Abundance of Arbuscular Mycorhizzal Fungi with Deforestation and Regeneration, Jacob O’Connor

Dimensions of Disaster During Hurricane Katrina: Landscapes, Levees, and the Least Fortunate, Sarah McKinnell

Acid Rock Drainage in the Upper Snake River: The Presence of Heavy Metals in a Mineralized Watershed, Garrett Rue

Biogas Emissions and Bioenergy Potential from a Palm Oil Mill Wastewater Treatment System in Southwestern Costa Rica, Hana Fancher

Abundance of Arbuscular Mycorhizzal Fungi with Deforestation and Regeneration, Jacob O’Connor

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Deforestation and land transformation are widespread in tropical regions of the world. Land transformation leads to loss of mineral nutrients and alteration and/or destruction of arbuscular mycorrhizal fungi (AMF) communities. AMF are important for plants to extract nutrients and water while increasing resistance to pathogens and herbivory. This study investigates the AMF abundance of 30 root samples from four different habitats associated with deforestation and regeneration: pasture, pasture edge, secondary and primary forest. Root samples were cleared (KOH), stained (Trypan Blue), and quantified using a modified version of the grid line-intersect method. Pasture samples had the lowest mean AMF abundance of 0.270 (SE =0.046). Pasture edge samples had a mean AMF abundance of 0.318 (SE=0.028). Secondary and primary forest samples had the highest mean AMF abundances of 0.389 (SE=0.036) and 0.413 (SE=0.036), respectively. Pasture edge did not differ significantly from other habitats, but pasture was different from secondary and primary forest (ANOVA, F=3.086, df=3, p=0.045; Student’s t multiple comparison, t=2.056, p<0.05). This trend suggests that land transformation disrupts AMF, but they are quick to recover in secondary forest. Therefore, AMF communities are not particularly resistant but appear to be resilient to land transformation.




La deforestación y transformación del suelo están ampliamente dispersos en las regiones tropicales del mundo.  La transformación de los suelos conlleva a la perdida de nutrientes minerales y la alteración o destrucción de las comunidades de hongos micorrizicos arbusculares (AMF por sus siglas en ingles).  AMF son importantes en la obtención de nutrientes y agua por parte de las plantas y aumentan la resistencia a patógenos y herbívoria.  Este estudio investiga la abundancia de AMF en 30 muestras de raíces de cuatro hábitats diferentes asociados con deforestación y regeneración (pastizal, borde de pastizal, bosque secundario y bosque primario).  Las muestras se limpiaron (KOH), tiñeron (Azul de Tripan) y se cuantificaron usando una versión modificada del método de intersección de líneas de cuadrículas.  Las muestras del pastizal tienen la abundancia promedio menor de AMF 0.270 (DE=0.046).  El borde del pastizal tiene una abundancia promedio de AMF de 0.318 (DE=0.028).  Los bosques secundarios y primarios tienen en promedio la mayor abundancia de AMF con 0.3889 (DE=0.036) y 0.413 (DE=0.036), respectivamente.  El borde no difiere significativamente de los otros hábitats, pero el pastizal es diferente de los bosques primarios y secundarios (ANOVA, F=3.086, df=3, p=0.045; Student’s t multiple comparison, t=2.056, p<0.05). Esta tendencia sugiere que la transformación de los suelos destruye los AMF pero ellos son capaces de recuperarse en un bosque secundario.  Sin embargo las comunidades de AMF no son particularmente resistentes pero parecen ser elásticas a la transformación del suelo.




Nearly one-half of tropical rainforests has been transformed by human activity (Vitousek, 1997).  Tropical Rainforest originally covered 12% of the Earth’s surface and now occupy less than 5% (Butler, 2006). Further, the rate of tropical deforestation remains alarmingly high (Ehigiator et al. 2011). When deforestation occurs, erosion leads to substantial soil degradation and loss of soil fertility (Numata et al. 2009). Soil degradation in these areas may include the destruction and/or alteration of certain mutualistic mycorrhizal fungi communities within the soil (Carpenter et al. 2001).

            Most species of plants in the tropics have mutualistic associations with arbuscular mycorrhizal fungi (AMF; Smith et al. 1997). These AMF penetrate cortical cells of roots and develop mycelia that help obtain mineral nutrients from the soil. The symbiosis also aids in nutrient cycling and helps to protect plants against environmental stress (Azcón-Aguilar et al. 1997). AMF associations increase the availability of nutrients like Phosphorus, Nitrogen, Copper and Zinc. This can increase resistance to pathogens and insect herbivory while increasing drought tolerance as well (Smith et al. 1997). Finally, mycelia and hyphal hairs of AMF increase soil aggregation by connecting soil particles and helping to decrease erosion (Rillig, et al. 2006). Overall, AMF are a foundation species (Bruno et al. 2003). They create conditions that enhance soil fertility, plant diversity and diversity of associated species.  When AMF are disrupted, as occurs with land transformation, soil fertility declines. Consequently, sustained agriculture becomes unlikely and limits to regeneration are created.

The cycle of tropical deforestation permits primary forest degradation to agricultural or pastureland. Because fertility is quickly depleted, the degraded land lies fallow.  Over time, some becomes secondary forest. This secondary forest can become an important repository of tropical biodiversity (Wright et al. 2006). Furthermore secondary forests are becoming more common. So common that most tropical forests in the future will be secondary growth (Wright et al. 2006) How AMF respond to this cycle of degradation and regeneration is important to understanding the resistance and resilience of tropical areas because AMF protect soil fertility and allow plant establishment. 

This study considers the effects of land transformation and regeneration on AMF abundance within superficial roots. AMF abundance was determined for four different habitats associated with forest transformation and regeneration: pastureland, pasture edge, and secondary and primary forest. Pasture will show how resistant AMF are to land transformation; pasture edge will illustrate the spatial scale that AMF respond to transformation. Secondary forest will indicate the resilience of AMF once regeneration occurs and primary forest will act as the control or original condition. 




Study Site


Samples for this experiment were taken from the Torres Family farm about 4 km Northwest of Santa Elena, Puntarenas, Costa Rica, in the area known as Cañitas (10°15’N, 84°46’W).  The area has a mean annual precipitation of 2519 mm with an additional 22% of precipitation coming from wind-driven mist; the mean annual temperature is 18.8°C (Clark et al. 2000). The farm lies at around 1300 m and has several distinct land-use areas within 38 ha, but samples were taken from pasture, pasture edge, and secondary and primary forest.   

            Thirty samples in total were collected from the 4 study sites (pasture n=6, pasture edge n=8, secondary forest n=8, primary forest n=8). In each site I only collected root samples from topsoil (surface to 10 cm depth). Root samples were generally no heavier than 3 grams. Each root sample was placed into labeled plastic bags (17 x 15cm) after removing as much topsoil as possible. The root samples were stored in the refrigerator until they could be stained. Storage time did not exceed one week.

            Pasture was situated on a moderate slope with cattle actively grazing. Edge site was positioned directly adjacent to the pasture with vegetation of 2-6m growing just outside a fence that bordered pasture. Secondary forest was beyond the pasture edge site and had vegetation of up to 6-10m. This particular section of forest had a regeneration period of greater than twenty years. The primary forest had vegetation-exceeding 10 m and was located on a different section of the farm isolated from other sample sites (Figure 1).





FIGURE 1.     Four habitats associated with forest regeneration. All located on the Torres family farm (Cañitas, Santa Elena, Costa Rica). (a) Pasture with visible slope. (b) Pasture edge that abuts the pasture. (c) Secondary forest just beyond the pasture edge. (d) Primary forest isolated from other sites but still within the property.


AMF Staining and Counting


I used a method of staining that was modified from two sources (Brundrett 1996, Vierheilig 1998). No more than two grams of roots from each site were initially cut into manageable pieces of less than 3 cm and then rinsed thoroughly to rid the samples of soil. Next the samples were placed in 100 ml beakers and completely covered in 10% Potassium Hydroxide (KOH). The mixture was boiled for 15 minutes. After ample time to cool, roots were rinsed with tap water to remove excess KOH. The beakers were also rinsed before the cleared roots were put back into them. Next the root samples were covered in a 5% Trypan Blue solution and boiled for 10 minutes, again giving ample time to cool before rinsing. Lastly, roots that were well cleared and stained (light blue color) were selected and placed on microscope slides.

I used a modified version of the grid line intersect method (Giovannetti, 1980) to quantify the AMF abundance. Once root samples were placed randomly on slides they were photographed under 400x magnification using a standard microscope adaptor. For each photograph I used a simple photo editor and heightened the contrast to ensure that the AMF bodies were clearly displayed. Then each photo was fitted with a 7X10 grid in order to find the proportion of AMF abundance (Figure 2).




FIGURE 2.     Photograph of root sample at 400x magnification with grid placed over to quantify AMF abundance. This particular sample had an AMF proportion of 0.457.  The upper left hand corner is empty space




Generally, pasture had lower AMF abundance than all other areas of regeneration (ANOVA, F=3.086, df=3, p=0.045). Areas with more regeneration time had higher AMF abundance and primary forest had the highest. Pasture samples had a mean AMF abundance of 0.270 (SE=0.046). Pasture edge samples had a mean AMF abundance of 0.318 (SE=0.028). Secondary forest samples had a mean AMF abundance of 0.389 (SE=0.036). Lastly, primary forest samples had the highest mean AMF abundance of 0.413 (SE=0.036) (Figure 3).

            Although there was a trend of increasing mean AMF abundance, not all habitats showed significant difference.  Pasture and pasture edge (difference of mean =0.048) showed variation, but their difference was not significant. While pasture edge and secondary forest were adjacent to one another, they did show a slight difference (difference in mean =0.071). Similarly, pasture edge and primary forest differed (difference in mean = 0.095), but there was not a significant difference. Secondary and primary forest differed in mean AMF abundance (difference in mean =0.023), but again there was no significant difference. In fact, secondary and primary forest had very similar AMF abundances. Finally, pasture differed significantly from secondary forest (difference in mean =0.119) and from primary forest (difference in mean =0.142; Student’s t multiple comparison, t=2.056, p<0.05).




FIGURE 3.     Mean arbuscular mycorrhizal abundance for various land use areas (pasture, pasture edge, secondary and primary) in Premontane Moist/Wet Forest of Pacific slope Costa Rica at approximately 1300 meters altitude. Abundance is percent area of root in longitudinal section infected.  Bars labeled A and B represent groups that are not statistically significant (p > 0.05). Data that do not share the same letter bar are statistically significant.




Overall I found that pasture had less mean AMF abundance than other sampled areas. This makes sense because the transformation from primary forest to pasture greatly alters AMF communities (Carpenter et al. 2001). While the AMF abundance was significantly lower than primary forest, pasture still maintained AMF communities. This implies that pasturelands are fairly resistant to land transformation. Ultimately, this trend suggests that once areas of tropical forests are transformed to pastureland, regeneration brings back AMF that may have been eroded away or destroyed.

It is important to note AMF mean abundances did vary slightly between pasture and pasture edge sites. This suggests that even after a very short period of regeneration, found in pasture edge areas, AMF can return. Pasture edge was also a measure of spatial scale so this gives us an idea of how AMF respond to land transformation spatially. Pasture edge was intermediate to pasture and primary forest, differing from neither significantly, but the change was fairly abrupt.  Additionally, neighboring Edge and Secondary forest also varied marginally in AMF abundances. This small difference in AMF abundance suggests that there is a gradual re-colonization of AMF in habitats of longer regeneration.

            Secondary and primary forest AMF abundances did not differ greatly. The secondary forest site in this study had a regeneration period of over 20 years while the primary forest site had never experienced large-scale disturbances or deforestation. This means that within 20 years AMF abundance can return to levels found before the land was transformed. In more general terms this implies that AMF are moderately resilient to land transformation.

 As forests regenerate from disturbances, and diverse vegetation returns, nutrients begin to accumulate once again (Feldpausch et al. 2004). Furthermore, these data suggest that AMF abundance increases with forest regeneration as well. Transformation from primary to pasture greatly reduces AMF.  This disrupts erosion control, nutrient load, etc.  The change is abrupt, as shown by the pasture edge.  However, once left fallow, even over a relatively short time span of 20 years, deforested land can return to primary forest conditions.  Thus, AMF are not terribly resistant but appear to be resilient.  This is good news for tropical biodiversity.  Deforestation of tropical primary forest leads to degraded land conditions. But when the land is allowed to regenerate, AMF –as a foundation species- rebounds quickly, allowing nutrient load to increase and biodiversity to return.   




I would like to thank my advisor, Alan Masters, for all of his advice and support during my investigation, Maricela Pizarro, for helping me understand some crucial aspects of mycorrhizal fungi. A huge thanks goes to the Torres family for letting me roam around their farm collecting root samples. Last but certainly not least I would like to thank CIEE and the remaining staff (José Carlos Calderón, Branko Hilje, and Johel Chaves) for allowing the use of their chemistry room and equipment and the Estación Biológica for providing delicious meals and cozy beds for my entire stay.




Azcón-Aguilar, C AND., J.M. Barea. 1996. Applying mycorrhiza biotechnology to horticulture: significance and potentials. Scientia Horticulturae 68: 1-24.

Brundrett, M., N. Bougher, B. Dell, T. Grove, AND N. Malajczuk. 1996. Working with Mycorrhizas in Forestry and Agriculture. Australian Centre for International Agricultural Research.

Bruno, J.F., J.J. Stachowicz, M.D. Bertness. 2003. Inclusion of facilitation into ecological theory. TRENDS in Ecology and Evolution 18: 119-125

Butler, R.A. “http://rainforests.mongabay.com/0101.htm” Mongabay.com / A Place Out of Time: Tropical Rainforests and the Perils They Face. 9 January 2006. .

Carpenter, F.L., S.P. Mayorga, E.G. Quintero, AND M. Schroeder. 2001. Land-use and erosion of a Costa Rican Ultisol affect soil chemistry, mycorrhizal fungi and early regeneration. Forest Ecology and Management 144: 1-17.

Clark, K.L., R.O. Lawton, AND P.R. Butler. 2000. Monteverde; Ecology and Conservation of a Tropical Cloud Forest. Oxford University Press, New York, New York.

Feldpausch, T.A., M.A. Rondon, E.C.M. Fernandes, S.J. Riha, AND E. Wandelli. 2004. Carbon and nutrient accumulation in secondary forests regenerating on pastures in central Amazonia. Ecological Applications 14: S164-S176.

Fischer, C.R., D.P. Janos, D.A. Perry, R.G. Linderman, AND P. Sollins. 1994. Mycorrhiza inoculum potentials in tropical secondary succession. Biotropica 26: 369-377.

Giovannetti, M., AND B. Mosse. 1980. An evaluation of techniques for measuring vasicular-arbuscular mycorrhizal infection in roots. New Phytologist 84: 489-500.

Numata, I., M.A. Cochrane, D.A. Roberts, AND J.V. Soares. 2009. Determining dynamics of spatial and temporal structures of forest edges in South Western Amazonia. Forest Ecology and Management 258: 2547-2555.

Rillig, M. C. AND D.L. Mummey. 2006. Mycorrhizas and Soil Structure. New Phytologist 171: 41-53.

Smith, S. E., AND D. J. Read. 1997. Mycorrhizal Symbiosis. Academic Press, San Diego, California.

Vierheilig, H., A.P. Coughlan, U. Wyss, AND Y. Piché. 1998. Ink and vinegar, a simple staining technique for arbuscular-mycorrhizal fungi. Applied and Environmental Microbiology 54: 5004-5007.

Vitousek, P.M., H.A. Mooney, J. Lubchenco, J. M. Melillo. 1997. Human domination of Earth’s Ecosystems. Science 277: 494-499.

Wright, S.J., H.C. Muller-Landau. 2006. The future of tropical forest species. Biotropica 38: 287-301.


Dimensions of Disaster During Hurricane Katrina: Landscapes, Levees, and the Least Fortunate, Sarah McKinnell 

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            In 2005 Hurricane Katrina made landfall in Southeastern Louisiana as a powerful Category Three hurricane. The hurricane protection systems in place for the city of New Orleans and surrounding parishes were overwhelmed sending billions of gallons of water into local communities. This atypical flood volume inundated 80% of New Orleans, impeding rescue efforts and devastating infrastructure and emergency resources. Over 1,500 lives were lost and an estimated 125 billion US dollars were spent on emergency response, recovery, and reconstruction. Hurricane Katrina is the worst disaster in the United States in over a century.

            This paper analyzes why Hurricane Katrina was such a catastrophe. Three major reasons for the disaster are identified: construction of piecemeal levee systems, wetland loss, and social vulnerabilities. Throughout the history of southeastern Louisiana’s settlement, the natural hydrography was manipulated in order to protect life and property from flooding; a fragmented levee system was constructed based on under estimated storm risk resulting in the hurricane protection system that failed during Hurricane Katrina. Similarly, increased residential development, canal building, and natural land subsidence processes have degraded natural wetlands which function as protective barriers from storm surges. The population of New Orleans exhibited high social vulnerabilities, as many Katrina victims lacked the tools, knowledge, and capabilities necessary to evacuate in a timely manner or to exercise other self-protective measures.

            These three elements—fragmented levee systems, wetland degradation, and high social vulnerabilities—exacerbate the level of vulnerability of property and people along the Gulf Coast. In order to reduce the vulnerability and the probability of a similar catastrophic event occurring, an analysis of Hurricane Katrina can be utilized to improve future mitigation planning. Better mitigation could yield improvements in levee quality; areas of dramatic wetland decline can be monitored and perhaps protected from future development, and heavily populated areas with high social vulnerabilities can be recognized and considered priority zones for mitigation plans.

Accronyms Commonly Used:


B-LLP             Barrier-Low-Level Hurricane Protection Plan

CWPPRA                   Coastal Wetlands Planning, Protection, and Restoration Act Managing Agency

EIS                  Environmental Impact Statements

FEMA                        Federal Emergency Management Agency

HLP                High-Level Plan

IHNC              Inner Harbor Navigation Canal

LPHPP                        Lake Pontchartrain Hurricane Protection Plan

MRC               Mississippi River Commission

MRGO                       Mississippi River Gulf Outlet

NASA             National Aeronautics and Space Administration

NHC               National Hurricane Center

NOAA                        National Oceanic and Atmospheric Administration

NWS               National Weather Service

SPH                 Standard Project Hurricane

USACE                       United States Army Corps of Engineers

USGS              United States Geological Survey



Table of Contents:



            The Storm                                                                               5


            The Geography of New Orleans                                                        10

The Construction of the Pre-Katrina Landscape                                                 The Crescent City: 1733 to 1927                                                       13

            Flood Management: 1927 to 1965                                                      16

            Reassessment and Repeated Mistakes: 1965 to 2005                                    21

Wetland Decline                                                                               25

Social Vulnerabilities                                                                                 30

Future Mitigation and Conclusions                                                          34

Afterword                                                                                           38

References                                                                                         40




Introduction – The Storm








Figure 1: Hurricane Katrina making landfall, August 29, 2005. NOAA Katrina Homepage.





            On August 29, 2005 Hurricane Katrina battered the low-lying lands of the central Gulf states (Johnson 2006). The eyewall of the Category Three storm crossed over southern Plaquemines Parish, Louisiana with maximum wind speeds of 125 miles per hour (NOAA 2007). The devastation was widespread across the Gulf Coast as Katrina’s damaging winds and storm surge stretched over 230 miles outward from the center (Graumann et. al 2006). The city of New Orleans was pummelled by heavy rainfall, 100+ mile per hour winds, and in some areas a storm surge of up to 28 feet (NOAA 2007). Eighty percent of the metropolis of New Orleans was inudated by flood waters; some areas such as the Lower Ninth Ward and Lakeview were under up to twenty feet of water (Graumann et. al 2006). Much of the infrastructure in New Orleans, such as transportation networks, schools, government buildings, and emergency response services were damaged leaving neighborhoods unrecognizeable, highways impassible, and electricity knocked out for over 1.7 million people (NOAA 2007). The storm overwhelmed protective seawalls and the intricate levee system in the region forcing hundreds of thousands of residents to evacuate or endure the dooms-day-like conditions. Hurricane Katrina claimed between 1500 and 1800 lives, making it the second most deadly hurricane event in U.S. history, second only to the Galveston Island, Texas hurricane of 1900 (NOAA 2007).

            In the weeks after the storm, Americans and the global community witnessed surreal imagery and tragic accounts of death and survival. The United States, one of the most developed and prosperous nations in the world, had endured a large-scale natural disaster. Looting and violence broke out, surviviors were forced to wait on rooftops and in shelters for days without access to potable water and food, and corpses floated through toxic waters (Johnson 2006). In New Orleans and surrounding parishes the polluted mire remained stagnant for up to 43 days after Katrina’s initial landfall (Johnson 2006).

            Two flood maps (Figure 2 and 3) demonstrate the magnitude of flood waters in New Orleans Parish and the length of time it took for the waters to recede or be pumped out (NOAA 2006). Figure 2 shows the depth of flooding two days after the storm on August 31, 2005. Much of the city was flooded by four to eight feet of water, with some areas such as New Orleans East inundated by up to fifteen feet of water. Figure 3 shows flood waters still present on September 20, 2005. It took until October 11, 2005 for the floodwaters to be completely drained from the city’s limits (Johnson 2006). Figure 4 and Figure 5 show before and after satellite imagery of the lower Mississippi River Delta. Flooding was extreme throughout Southeastern Louisiana in addition to the New Orleans metropolitan area.




Figure 2: New Orleans Flood Map – August 31, 2005. Source: NOAA Flood Maps 2006.



Figure 3: New Orleans Flood Map – September 20, 2005. Source: NOAA Flood Maps. 2006.



Figure 4: MS River Delta flooded from Hurricane Katrina on September 4, 2005. The coloring has been amplified to make the landscape changes more apparent. Source: NASA Earth Observatory Terra-MODIS Satellite Imagery.2005.







Figure 5: MS River Delta unflooded on August 9, 2005. The coloring has been amplified to make the landscape changes more apparent. Source: NASA Earth Observatory Terra-MODIS Satellite Imagery. 2005.




Hurricane Katrina Floods the Southeastern United States


            Hurricane Katrina had surprisingly large impacts; however, Hurricane Katrina was not the strongest storm in history to make landfall on the Gulf Coast. Hurricane Camille struck the same region of the central Gulf States in 1969 as a Category Five storm according to the Saffir-Simpson Hurricane Scale (Table 1). This scale is based upon a hurricane’s maximum wind speed: categories three through five are considered major hurricanes, with categories four and five resulting in catastrophic damages and losses (Graumann et. al 2006). At one point during its formation Hurricane Katrina was considered a Category Five storm, but the winds died down considerably before making landfall in Louisiana on August 29 (Roth 2010). In the same 2005 hurricane season, Hurricanes Rita and Wilma also reached Category Five status and made landfall as intense Category Three hurricanes (Roth 2010). Yet, Camille, Rita, and Wilma did not produce the extensive and widespread flooding and damage witnessed during Hurricane Katrina.


Table 1: Categorization of hurricanes’ strength based upon wind speed. Source: Graumann et al. 2006.



The aftermath of Hurricane Katrina reveals continued vulnerability to natural disasters even for a highly developed nation and a region that has experienced many hurricane disasters. The storm exposed the shortcomings of engineering as well as emergency response. In order to reduce the likelihood of future hurricane losses in the Gulf states and other exposed coastal geographies, an analysis of the impact of Hurricane Katrina, with attention to the weaknesses in adaptation that it revealed, can provide lessons and insights into the relationships between humans and the environment that make the region vulnerable. This paper proposes three main reasons for the extent of destruction during Hurricane Katrina: piecemeal levee and seawall construction, wetland and natural buffer zone decline exacerbated by development of unsuitable lands and natural subsidence processes, and high levels of social inequalities that resulted in an extremely vulnerable population of non-evacuees. Analysis of these three key components could yield insight to improve future mitigation, prevention, and planning systems.



Background – The Geography of New Orleans

            The Mississippi River Delta is a low-lying geographic region characterized by wetlands, estuaries, and the meandering Mississippi River (CWPPRA 2011). The River Delta is located between Mississippi and Lousiana where the Mississippi River makes its way to the Gulf of Mexico (CWPPRA 2011). The river dominates the landscape of southeastern Louisiana and southwestern Mississippi, creating an alluvial valley with routine flooding (Miller and Rivera 2008). Geologic sediment samples indicate that the river has changed its route to the Gulf of Mexico through time depending on land elevation, sediment composition, and sea level (Van Heerden and Bryan 2006); this indicates a transient state for the entire delta-plain. Van Heerden and Bryan refer to the Louisiana coastal zone as a "living landscape", which exhibits a dynamic balance between sediment deposition and recession (2006, p 153). Before early settlement and land development, cypress swamps and marshes extended further south of Lake Pontchartrain than seen today (Kindinger 2001). Similarly, the barrier islands in the Gulf of Mexico were more prominent, acting as a natural line of defense against hurricane storm surges (Kindinger 2001). Today, the living landscape of Louisiana exists as an amalgamation of concrete, swamp, river, and infrastructure with high levels of wetland decline. (NASA 2005).

            New Orleans is referred to as the “Crescent City” due to its crescent-moon-like curvature along the banks of the Mississippi River (Miller and Rivera 2008). To the north of New Orleans, a levee system outlines the coast of Lake Pontchartrain, a large brackish water estuary that provides habitat for flora and fauna as well as recreational opportunities for surrounding populations (Moreau 2006). To the east, Orleans Parish is bordered by the Inner Harbor Navigation Canal (IHNC) otherwise known as the Industrial Canal (Moreau 2006); beyond the IHNC is New Orleans East, a newer residential section bordered by Lake Borgne, the gateway to the Gulf of Mexico (Moreau 2006). New Orleans and neighboring parishes are bordered to the south by the Mississippi River as it winds its way into the Gulf of Mexico (Moreau 2006); to the west of Orleans Parish lies the 17th St. Canal and Jefferson Parish (Moreau 2006).

            The major water features of New Orleans along with notable neighborhoods and roadways are visible in Figure 6. Figure 6 shows that New Orleans is bordered by water on all sides; to the north there is Lake Pontchartrain, to the east the IHNC which connects to the southern border of the Mississippi River, and then the 17th St. Canal on the western border which reconnects with Lake Pontchartrain. In addition to being surrounded by water, the city basin is located mostly below sea level with some areas up to eight feet below the sea surface (Figure 7). The low elevation of the city is problematic as the entire region is susceptible to flooding and storm surges. Figure 7 (below) reveals the predicament of New Orleans’ bowl-like geography. In flooding situations, the surrounding water features spill into the areas lying below sea-level, inundating most of the city.


Figure 6: A generalized map of prominent New Orleans features and the surrounding water systems. Source: Rogers, J.D. 2008.















Figure 7: Elevation of New Orleans and surrounding parishes. Scale: 1: 700,000. Source: Kosovich, John J. 2008.





The Construction of the Pre-Katrina Landscape – The Crescent City: 1733 to 1927

            The night before Hurricane Katrina struck the central Gulf region, the landscape existed as a product of hundreds of years of human alteration. The history of New Orleans is marked by frequent hurricanes, storm surges, and river flooding events; these events were perceived as manageable by early white settlers of the Mississippi River Delta (Miller and Rivera 2008). Beginning with the founding of New Orleans in 1733 by French colonists a precept was spread: the New Orleans region was a gateway that must be tamed in order to establish a pivotol port that would bring prosperity to the land (Miller and Rivera 2008). The mouth of the Mississippi was seen as a tempestuous entity and simultaneously as a financial wellspring. Miller and Rivera describe this desire to conquer the “shortcomings of the New Orleans topography” as “surprising evidence of what men will endure” (2008, p 26). The annual drowning of the land and non-routine flooding from frequent storms would prove to be harder to manage than originally believed, and they continue to be a “shortcoming” of the Mississippi River Delta today.

            Initially, the Crescent City was developed to have a network of roadways known as the “sixty-six block grid” (Miller and Rivera 2008). The sixty-six block grid was built on the highest ground between the Mississippi River and Lake Pontchartrain (Miller and Rivera 2008). This business epicenter did not provide enough housing for early settlers, however, which led to the establishment of “faubourgs”, or suburbs (Miller and Rivera 2008). The faubourgs were built to the north and west of the sixty-six block grid in low-lying, swampy areas. The faubourgs were subject to overspill from the neighboring Lake Pontchartrain during storm events, in addition to seasonal flooding from the Mississippi River (Miller and Rivera 2008). In order to cope with the annual saturation of the land, local farmers and land owners buffed up the landscape’s natural levees (Miller and Rivera 2008). There was neither congruency nor communication between levee systems and their constructors, resulting in a piecemeal and permeable “system”; this in turn caused continued flooding of the terrain (Miller and Rivera 2008).

            Major levee failures occurred during the city’s first century as a port. Notably, on May 5, 1816 and May 4, 1849, the Mississippi River breached the levees flooding St. Charles Place and the French Quarter (the sixty-six block grid) with up to eight feet of water (Miller and Rivera 2008). In addition, major hurricanes afflicted the region. The “Great Louisiana Hurricane” on August 9, 1812 sent fifteen feet of water into St. Bernards Parish just across the river from New Orleans proper; the “Great Barbados Hurricane” of 1831 swelled the levels of Lake Pontchartrain, creating a three foot storm surge that flooded New Orleans’ suburbs (Miller and Rivera 2008). During this era, the highest levee in New Orleans was a natural levee composed of silt deposits (Van Heerden and Bryan 2006). This levee stood ten feet above the city floor, which rested nearly eight feet below sea level, indicating only a two foot wall above sea level of protection from storm surges and annual flooding (Van Heerden and Bryan 2006).

            The mid-to-late-nineteenth century again saw major flooding of the Mississippi River. Local governments were in charge of the levees and floodwalls up until the 1860s, when the U.S.  federal government decided to provide financial assistance in order to establish a “continuous levee system” (Miller and Rivera 2008, p 29). This continuous system was proposed as a method to resolve seasonal flooding in the New Orleans area and to benefit navigation networks, not to provide flood protection from hurricanes (Miller and Rivera 2008). Thus, the levee construction was organized around containing the swelling of the Mississippi River, not providing protection along the Gulf of Mexico or from Lake Pontchartrain.

            In need of an overarching organization to manage levee building, in 1879 the U.S. government established the Mississippi River Commission (MRC) headed by the United States Army Corps of Engineers (USACE); the MRC was designed to be in charge of levee and canal construction and development for the entire Mississippi River Delta (Miller and Rivera 2008). The MRC initially set out constructing levees to support navigation and channeling in the Mississippi River Delta, but after widespread severe flooding in 1927, the U.S. government mandated that levee building and canal construction provide flood and storm surge protection to prevent life and property losses within the delta region (Van Heerden and Bryan 2006).

            The federal government shifted the focus of levee construction towards flood management due to the increasing population in New Orleans. From 1900 to 1950 the population doubled in size (USGS Coastal and Marine Geology Program 2010). Table 2 demonstrates the dramatic increase in New Orleans’ population from 1900 to 1950 (USGS Coastal and Marine Geology Program 2010). This escalation prompted new development in areas further away from the highest ground at the city center (Moreau 2006).  These suburbs were built on below-sea-level, wetland terrain, creating communities that were vulnerable to flooding (Van Heerden and Bryan 2006). This new development also necessitated new levees.


Table 2: Population of New Orleans Chart. Source: USGS Coastal and Marine Geology Program. 2010.

New Orleans Historic Growth            From its early settlement, New Orleans was a region marked by fluxing and tempestuous

water features. The shortcomings of the regional

topography, however, were considered to be

problematic but controllable. Despite repeated flooding events, development increased and the population expanded. In order to improve navigation canals and handle seasonal flooding for the growing city, the MRC was created to oversee levee construction for the lower-river delta. In 1927, nearly two centuries after New Orleans was founded, the purpose of levee construction was shifted towards hurricane protection. The early history of New Orleans suggests that the region was quickly over-populated and under-protected, leaving the dilemma of how to protect lives and property to future generations.



The Construction of the Pre-Katrina Landscape – Flood Management: 1927 to 1965

            From 1927 to 1960 the USACE constructed the levee and canal system that remains the heart of the modern levee system in place in New Orleans (Van Heerden and Bryan, 2006). Floodwalls were built in front of earthen levees to bar off Lake Pontchartrain, the Jefferson Parish levee and the INHC were constructed, and the Mississippi River’s seasonal inundation of New Orleans was mitigated by the construction of the Bonnet Carre Spillway, just 23 miles north of New Orleans (Moreau 2006; NOAA 2011). The Bonnet Carre Spillway is a floodgate-controlled outlet that can redirect up to 250,000 cubic feet of water per second into Lake Pontchartrain (NOAA 2011). The Spillway is currently still in use; its construction prevented what geologists predict would have been an eventual merging of the Mississippi River and the Atchafalaya River (Van Heerden and Bryan 2006). By redirecting seasonal floodwaters, the Bonnet Carre Spillway has allowed the Mississippi River to maintain its current flow path instead of fluxing in the direction of its overflowing waters (NOAA 2011).

            With seasonal flooding “under control”, the U.S. federal government sought to expand protection for storms. In 1965, Congress instructed the USACE to devise a hurricane and severe tropical storm protection plan that could harbor New Orleans from even the most severe of storms (Moreau 2006). The USACE proposed the Lake Pontchartrain Hurricane Protection Plan (LPHPPP) that was designed to protect the area from the Standard Project Hurricane (SPH) (Moreau 2006). The Standard Project Hurricane was described by the USACE as “the one that may be expected from the most severe combination of meteorological conditions that are reasonably characteristic of the region” (Moreau 2006, p 27). The USACE estimated the maximum winds of the SPH to be 100 miles per hour with a return period of two-hundred years, or an annual probability of .5% (Moreau, 2006, p 27). A return period refers to what Smith and Petley define as “the time that, on average, elapses between two events that equal, or exceed, a given magnitude” (2009, p. 55). In other words, the SPH, a Category Three hurricane on the Saffir-Simpson Scale, was expected to occur on average every two-hundred years.

            The LPHPP contained two potential protection designs: the Barrier-Low-Level Hurricane Protection Plan (B-LLP) and the High-Level Plan (HLP) (Moreau 2006). The B-LLP involved dredging wetlands for barrier enhancement of the current levee system (Moreau 2006). The HLP was more costly and called for floodgates to be constructed at major canal entrances, functioning as a blockade to storm surges (Moreau 2006). The floodgates could be closed before storms made landfall, preventing storm surges from rushing up canals and flooding the local neighborhoods (Moreau 2006). The Mississippi River Commission, which was now comprised of local levee bureaus, federal emergency management groups, and the USACE, chose to implement the B-LLP; however, both the B-LLP and the HLP were modelled after an undercalculated SPH (Richardson et al 2008).

            Recent calculations performed by researchers at the National Hurricane Center and the National Weather Service (NWS) indicate that rather than a two-hundred year return period of a Category Three hurricane making landfall in southeastern Louisiana, there is a twenty year return period (Blake et. al 2011). Figure 8 represents return periods of a Category Three strength storm or higher making landfall for the eastern coastal U.S. counties. Louisiana has one of the shortest return intervals, along with the southern coast of Florida and the coast of North Carolina, indicating a substantial under estimation by the USACE.


Figure 8: Estimated return periods for U.S. counties of a Category Three Hurricane or stronger making landfall. Blake et al. 2011.


            Table 3, created by David Roth in conjunction with the NWS and NOAA, displays the number of hurricanes and tropical storms to strike the coast of Louisiana from 1850 through 2000 (2010, p 7). Striking refers to the eye-wall or a portion of the eye-wall passing over part of the state of Louisiana. Fifty-four hurricanes were reported to have made landfall in a one-hundred and fifty year time period; this indicates that a hurricane should be expected to make landfall in Louisiana on average every 2.8 years (Roth 2010). In the 1960s alone, four hurricanes that struck Louisiana, three of which matched or surpassed Category Three intensity (Roth 2010). This again would indicate a major underestimation of the SPH’s return period.












Table 3: Table displaying Hurricane or Tropical Storm strikes for the entire state of Louisiana. Source: Roth, David. 2010.









            Besides a miscalculated return period, a case can be made that the USACE underestimated the intensity of the SPH; hurricanes of greater magnitude have directly and indirectly struck the Mississippi River Delta (Blake et al 2011). In 1969, just four years after the LPHPP was proposed, Hurricane Camille made landfall on the border of southeastern Louisiana and southwestern Mississippi as “the most intense hurricane known to ever make landfall in the United States” based upon wind speed and storm pressure (Roth 2010, p 42). Camille hit the coastline as a powerful Category Five hurricane on the Saffir-Simpson Scale (Roth 2010). Also, four Category Four hurricanes have struck the Louisiana coast from 1850 to 2004 (Moreau 2006). Two out of these four hurricanes to affect Louisiana occurred within the decade prior to the USACE’s LPHPP proposals. Although they made landfall in southwestern Louisiana and eastern Texas, Hurricane Audrey of 1957 and Hurricane Carla of 1961 were both stronger hurricanes than the SPH, and both created storm surges in the Mississippi River Delta that led to flooding in the New Orleans area (Roth 2010). The same year that the LPHPP was produced, Hurricane Betsy, a strong Category Three storm, struck just east of New Orleans (Roth, 2010). Betsy created a storm surge of over ten feet along the Mississippi River, sending nine feet of water into New Orleans East and Chalmette, inundating these regions for days (Roth 2010).  

            It is important to note the underrated SPH, because it justified the piecemeal levee system. If the SPH had been made equivalent to a Category Five hurricane, thus necessitating a superior hurricane protection plan, the fragmented construction and restoration produced by the LPHPP would not have been acceptable. However, the SPH was used as the framework for the New Orleans hurricane protection system for the next fifty years, and the lower sense of risk may have contributed to the catastrophe produced by Hurricane Katrina (Moreau 2006).





The Construction of the Pre-Katrina Landscape – Reassessment and Repeated Mistakes: 1965 to 2005

            The LPHPP construction, based upon the Barrier-Low-Level Protection Plan, did not commence until the late 1970s (Rogers 2008). When construction finally did start, it was carried out in a piecemeal fashion (Rogers 2008; ASCE 2007). Concrete was added to the French Quarter levee, levees at the east end of Plaquemines Parish were raised and fortified, and steel-sheet pilings were used to strengthen the IHNC (Van Heerden and Bryan 2006). These improvements benefitted specific areas of New Orleans, but the USACE neglected smaller communal levees in order to revamp the larger ones first (Rogers 2008). Thus, the smaller, local levees were reinforced to the USACE’s height standards by local levee boards, not the Army Corps of Engineers (Rogers 2008; ASCE 2007). While built up to USACE height standards, the local levee boards neglected to enlarge the levees’ bases, adding weight to a weakening base (Rogers 2008; ASCE 2007). Notably, the local levee boards made reinforcements along the 17th St. Canal levee and the London Avenue Canal levee, two levees that were breached by storm surges from Lake Pontchartrain during Hurricane Katrina (ASCE 2007).

            By 1982, about 50% of the hurricane protection system was completed (Van Heerden and Bryan 2006). The slow rate of construction was largely due to federal and state funding constraints and new legislation passed by Congress, such as the Environmental Policy Act and the Clean Water Act, that required Environmental Impact Statements (EIS) (Moreau 2006). The EIS that the USACE drafted resulted in a forced shut down of barrier enhancement projects, because much of the B-LLP called for dredging and wetland removal in order to maintain levees and support canals, measures that did not meet the terms of environmental legislation (Moreau 2006). Furthermore, while complying with federal requirements, the USACE also had to work with local levee boards within the Mississippi River Commission (Rogers 2008). Most local levee bureaus supported less costly improvement plans in order to save taxpayer dollars (Rogers 2008). Alternative plans, such as the grandious HLP, would have added an unsightly 300 meter-wide embankment on the shores of Lake Pontchartrain, along with the massive floodgates displacing some homes along the coast (Rogers 2008); local officials and communities would not agree to such disruptions (Rogers 2008). 

            In response to the slow onset of construction, the U.S. government instructed the USACE to reassess the 1965 LPHPP (Moreau 2006). The reevaluation began in 1984, upon which the USACE noted that the protection in place at the time was incomplete and not adequate enough to protect against the SPH (Richardson et. al 2008). In addition, levees and floodwalls in certain areas were found to be lower than their specified height and lacking uniform construction materials (Richardson et al 2008). This evaluation prompted two new plans for hurricane protection in the region: the Parallel Protection Plan and the Frontal Protection Plan (Moreau 2006). The USACE endorsed the Frontal Protection Plan which would build floodgates and high-functioning pumps at all major canal entrances and create a massive floodgate at the entrance to Lake Pontchartrain (Van Heerden and Bryan 2006); this plan would prevent storm surges from being able to enter the city through the canals and Lake Pontchartrain, effectively eliminating a significant portion of flooding in New Orleans (Moreau 2006). The local levee boards, however, supported the Parallel Protection Plan, which yet again called only for elevating the floodwalls and levee systems around the canals and included some barrier enhancement along the Pontchartrain lakefront (Moreau 2006); this further exacerbated the fragmented network of levees, because reinforcements were not uniform across the levee system (ASCE 2007).

            Federal and state funding was allocated for the Parallel Protection Plan (Moreau 2006). Piecemeal construction ensued in which different materials were used to attach sections of one type of levee system to another (ASCE 2007). Figure 9 depicts levees at the 17th St. Canal and the London Avenue Canals in which the USACE connected concrete reinforcements with steel-sheet piling reinforcements (ASCE 2007, p. 64). Nearly all areas where this sort of bridging between two different levee styles occurred failed during Hurricane Katrina (ASCE 2007). Of the 350 miles of levees and floodwalls, 169 miles were damaged during the storm, and roughly 50 locations were either breached or overtopped by the storm surge (ASCE 2007).


Figure 9: Levees demonstrating use of different building materials; these levees failed during Katrina. Source: ASCE. 2007.




            Additionally, levee and floodwall elevations varied throughout the network (ASCE 2007). While the Army Corps of Engineers mandated specific height requirements, these requirements differed depending on the materials used in levee section (ASCE 2007). For example, the type of floodwall known as the “I-Wall” called for an earthen levee to support its frame higher than a regular earthen barrier (ASCE 2007). When these two sections were connected, the I-Wall levees stood significantly higher than the earthen levees. Figure 10 reveals a portion of the 17th St. Canal levee in which this scenario occurred. The I-Wall levee was connected to an earthen barrier, the barrier was lower in elevation, and the lower barrier was overtopped by the powerful storm surge (ASCE 2007).


Figure 10: 17th St. Canal – Different elevations of levees along the same canal resulted in overtopping of the lower sections during Hurricane Katrina.. Source: ASCE. 2007.


            The Army Corps of Engineers estimated finishing the Parallel Protection Plan by 2008; later adjustments pushed that date back to 2015 (Moreau 2006). Hurricane Katrina made landfall in Louisiana on August 29, 2005, ten years before levee refurbishment was set to be complete. Even if the levee construction had been completed before Katrina struck, the Parallel Protection Plan was still modeled after the Standard Project Hurricane, leaving the city of New Orleans at the mercy of a powerful Category Three hurricane (ASCE 2007). David H. Moreau, a researcher at the University of North Carolina at Chapel Hill, considers the history of the New Orleans levee system a “repititious cycle” of expansion and development, construction and protection, landscape manipulation and degradation, and failure followed by new development (2006, p. 11). Moreau criticizes the U.S. Army Corps of Engineers stating that they had an “overreliance on 50-year-old forecasts” that they used to “justify their projects” (2006, p. 11).

            The levee system in New Orleans that faced Katrina in 2005 was what the American Civil Society of Engineers called “a system in name only – in reality it is a disjointed agglomeration of individual projects that were conceived and constructed in a piecemeal fashion” (ASCE 2007, p 63). Had the system been built with congruencies throughout and based upon the maximum possible hurricane, catastrophe might have been averted.

Wetland Decline

            Wetland decline has become a serious and complex issue for southeastern Louisiana. The wetlands provide ecosystem services by protecting inland regions from storm surges, functioning as sponges during heavy flooding events, and filtering out pollutants in the water (USGS Coastal and Marine Geology Program 2010). Over the past 150 years the Lake Pontchartrain watershed has been transformed by massive drainage of low-lying basins, cypress swamps, and marshes (Kindinger 2001). Estimates from the NASA Earth Observatory indicate that from 1937 to 2000 up to 35 square miles of coastal wetlands were lost per year, or approximately 1,900 square miles of wetlands disappearing in 63 years (NASA 2005). The three main causes of this swift wetland decline are natural land subsidence processes, rapid growth and urban expansion, and canal dredging (USGS Coastal and Marine Geology Program 2010; CWPPRA 2011; Van Heerden and Bryan 2006; Moreau 2006).

            The wetlands of southeastern Louisiana are part of the Pontchartrain Basin watershed making up one of the largest estuaries in the United States (Kindinger 2001). The basin is situated to the east of the Mississippi River and extends northward through Jackson, MS (USGS Coastal and Marine Geology Program 2010). The southern extent of the Pontchartrain Basin joins with the Mississippi River Delta creating a landscape of fresh water swamps, brackish water estuaries, and salt water marshes (USGS Coastal Marine Geology Program 2010). The soils in and around Lake Pontchartrain are mostly comprised of silts, clays, and sands along with organic material such as leaf litter, shells, and rootlets (Kindinger 2001). These marshy soils are often saturated with water creating a highly compressible, unstable land surface (Van Heerden and Bryan 2006).

            The American Civil Society of Engineers noted that, “New Orleans is sinking” (ASCE 2007, p 8); the land undergoes a process known as subsidence, a natural process of soil compression due to the decay of the organic materials present in the soils (ASCE 2007). Before human intervention in the natural hydrology of New Orleans, land subsidence was counterbalanced by sediment deposition from the Mississippi River, maintaining an at-sea-level landscape; however, fresh sediment layers are now prevented from deposition over old layers due to the massive flood control systems established along the entirety of the Mississippi River (ASCE 2007). This has resulted in the below-sea-level surfaces present today. Hence, the flood control measures taken in the last two centuries, such as the construction of the Bonnet Carre Spillway, have actually sped up natural land subsidence processes creating a sinking city (NASA 2006).

            It is important to note that the land is sinking when discussing wetland decline in southeastern Louisiana, because land subsidence has been attributed as one of the leading factors in wetland decline in the New Orleans region; land subsidence allows increased levels of salt water to infiltrate sensitive brackish water wetlands (CWPPRA 2011). Brackish water estuaries comprise 24% of the total wetlands in the Pontchartrain Basin, functioning as protective, salt water barriers for inland fresh water marshes and cypress swamps (CWPPRA 2011). Due to land subsidence, the brackish water marshes have been more susceptible to encroaching salt water from the Gulf of Mexico (CWPPRA 2011). Even subtle changes to the amount of salt water in a brackish water ecosystem can have severe consequences, such as the inability of wetland vegetation to adapt to the rapid changes in saline content resulting in high levels of plant die-off and wetland loss (CWPPRA 2011).

            Increased saline levels in brackish water ecosystems is crucial for the Crescent City, New Orleans East, and the eastern bordering wetlands. New Orleans East historically has had the greatest land subsidence throughout the delta plain, and the region is already five to eight feet below sea level (NASA 2006). New Orleans East also has a large land area covered by wetlands and is bordered by the Borgne Land Bridge, the largest brackish water marsh in the region (CWPPRA 2011). The Borgne Land Bridge separates Lake Borgne and the Gulf of Mexico from Lake Pontchartrain, functioning as a line of defense from damaging storm surges (CWPPRA 2011). Research conducted by the Coastal Wetlands Planning, Protection, and Restoration Act Managing Agencies (CWPPRA), a conglomeration of NOAA, USACE, the National Resources Conservation Service, and more, has shown that since 1932 approximately 24% of the Borgne Land Bridge has been lost, largely due to land subsidence and the resulting spike in saline content (2011). Consequences from such a high rate of wetland decline include increased erosion along the shorelines of Lake Pontchartrain and Lake Borgne, further exacerbating the issues of wetland loss, and increased storm surges passing from the Gulf of Mexico through Lake Borgne to Lake Pontchartrain, putting more people and property at risk to flooding (CWPPRA 2011).

            In addition to land subsidence, increased development of wetland regions has led to substantial wetland decline. When the population of New Orleans was booming in the late 1800s and early 1900s, areas outside of New Orleans Proper were sought for development (Moreau 2006). Figure 11 depicts the city of New Orleans before the districts of Lakeview and Gentilly were built in 1849 (ASCE 2007). The land cover feature that separated central New Orleans from Lake Pontchartrain was freshwater marshes and cypress swamps (Moreau 2006). The swamps acted as a buffer from lake-side flooding or flooding from storm surges that could assault New Orleans from the north, the same direction as one of the two main storm surges that Hurricane Katrina produced (ASCE 2007). As lakefront development was seen as the next best step for the city the swamps were drained, resulting in significant wetland die-off (Moreau 2006). Furthermore, soils from other wetlands were collected and redistributed in the form of floodwalls along the shores of Lake Pontchartrain to protect the new developments (Moreau 2006; USGS Coastal and Marine Geology Program 2010). This was known as the Lakefront Development Project of 1926 that resulted in significant wetland drainage and loss (Moreau 2006).












Figure 11: Historical Map of New Orleans displaying former swamp lands to the north of the city. Source: ASCE. 2007.





            In terms of development, the greatest devastation to local wetlands occurred between 1950 and 2000 when the brackish water, marsh land barrier east of the IHNC was urbanized. Deemed a “high-risk venture” by the USACE because of its exceedingly low elevation, the federal government supported levee construction east of the IHNC so that new residential areas could be built, the region is now called New Orleans East (Moreau 2006, p 24). The notion that the New Orleans region would need additional residential land cover came from population projections modeled after the rate of growth from 1900 to 1950, in which the population of New Orleans doubled (USGS Coastal and Marine Geology Program 2010). However, the rate of population growth leveled out in the New Orleans area soon after the population boom, negating the full need of the New Orleans East developments (USGS Coastal and Marine Geology Program 2010). As a result, the wetlands were replaced by non-porous infrastructures that were not necessary to the city’s overall expansion, and the natural wetland barrier was destroyed.

            In conjunction with the promoted development of New Orleans East in the 1950s, federal and state government also sought to build a shorter navigation route from the Gulf of Mexico to the Port of New Orleans (USACE 2012). The proposed canal would have a duel function as a safer shipping route while encouraging residential settlement in New Orleans East (USACE 2012). The canal was named the Mississippi River Gulf Outlet (MRGO, pronounced “Mister Go”) and was completed in 1968 (USACE 2012). MRGO allowed ships to avoid the unpredictable mouth of the Mississippi River and saved shippers time by cutting off the remaining 120 miles of the winding lower Mississippi River (USACE 2012). Figure 12 displays MRGO beginning in the Gulf of Mexico and joining up with the IHNC.


Figure 12: Map of MRGO – demonstrates quicker, more direct route to Port of New Orleans. Source: USACE. 2012.


Map showing the location of the Mississip River Gulf Outlet (MRGO)            Throughout its construction and usage, MRGO has had profound effects upon the surrounding ecosystems. The 38-foot-deep and 500-foot-wide canal was dredged through brackish water marshes, cypress swamps, and smaller bays (USACE 2012). In fact, the construction of the 75 mile long MRGO directly removed

27,600 acres of wetlands and salinized tens of thousands of additional acres of sensitive wetland habitats (Freudenburg et. al 2008). Rather than an “outlet”, MRGO functioned as an “inlet” for salt water to bombard sensitive fresh and brackish water vegetation (Freudenburg et al 2008). In addition, MRGO served as a funnel for the storm surge during Hurricane Katrina, which resulted in multiple levee breaches along the IHNC, the major cause of flooding in St. Bernard’s Parish, the Lower-Ninth Ward, and New Orleans East (ASCE 2007; Freudenburg et. al 2008). This flooding was not only problematic for people and property, but also devastated the surrounding wetland ecosystems (Freudenburg et. al 2008).

            MRGO is just one of multiple canals that characterize the lower-river delta. Other canals have been constructed by oil and gas companies in order to better navigate the oil and gas-rich marshlands (Van Heerden and Bryan 2006). While MRGO and the canals constructed by the oil companies served to improve the navigation of the Mississippi River Delta, they did so at the expense of the region’s natural hurricane defense system (Freudenburg et. al 2008).

            When Hurricane Katrina collided with southeastern Louisiana, the network of wetlands that protected the coastline had been hindered by an amalgamation of human influence and natural processes. Because of land subsidence and saline encroachment, development, and canal dredging, Katrina struck a deteriorating, sensitive landscape that was unable to function as an absorbent barrier. These factors have crippled the wetlands of southeastern Louisiana and may have exacerbated the damages produced by Hurricane Katrina.



Social Vulnerabilities

            The reasons for Hurricane Katrina’s destruction were not limited to preexisting features of landscape and piecemeal engineering. The citizens of the Mississippi River Delta were also struck by a storm that altered their lives forever. Estimates of lives lost during Hurricane Katrina range from 1300 to as high as 1800 (Richardson et. al 2008); yet, studies performed by NOAA and the NWS suggest accurate disseminations of warnings with sufficient time to evacuate the New Orleans region (Johnson 2006). Research by Joseph E. Trainor et. al suggests that non-evacuees were in fact aware that a powerful storm was headed their way (2006). With a functioning warning system in place, many were left questioning why there were such devastating consequences. Susan L. Cutter, Christopher T. Emrich, and fellow social scientists argue that “social vulnerabilities” of the non-evacuees resulted in a very high number of “excess mortalities” or untimely deaths (Cutter and Emrich 2006; Trainor et. al 2006; Gall 2011, p. 159).

            Social vulnerabilities are defined as “the susceptibility of social groups to the impacts of hazards, as well as their resiliency, or ability to adequately recover from them” (Cutter and Emrich 2006, p. 103). Social vulnerabilities are byproducts of preexisting social inequalities; they embody population characteristics such as age, gender, and class as well as personal factors such as physical mobility, knowledge and awareness of evacuation routes and emergency services, social networks, fears of looting or physical harm, and more (Cutter and Emrich 2006; Trainor et. al 2006). Trainor et. al describes people with social vulnerabilities as not having “the means” to evacuate or execute other self-protective measures (2006, p. 314). Many citizens of New Orleans were without the means, forcing them to weather the storm with limited resources and aid (Trainor et. al 2006).

            Different social vulnerabilities have been identified as the primary cause of such high death tolls and such high rates of non-evacuation. Cutter and Emrich note that two of the greatest determinants of social vulnerability in Orleans Parish were race and class (2006). Most of the non-evacuees during Hurricane Katrina were lower-class, African-American citizens (Cutter and Emrich 2006). Cutter and Emrich note that 27% of this particular demographic did not own an automobile, hindering their ability to evacuate. Additional research by Melanie Gall indicates that age may have been the most influential social vulnerability during Hurricane Katrina (2011). An analysis of the victims of Hurricane Katrina indicated that 50% of the victims were older than 75 years old, and 85% of the victims were 51 years or older (Gall 2011). Although age itself does not necessarily make an individual more vulnerable, it’s correlated with reduced physical and mental abilities and chronic diseases (Gall 2011). This implies that many Katrina victims may not have been able to mobilize quickly, if at all, or comprehend the impending dangers.

            Trainor et. al sights a different social vulnerability as playing a highly significant roll in the Katrina disaster. Trainor et. al interviewed non-evacuees asking why they did not or could not evacuate. Non-evacuees suggested the following reasons for remaining at home during the storm: physical immobility, financial limits/costs, lack of personal transportation, government failure to provide transportation, lack of knowledge of evacuation routes, lack of knowledge of public emergency protocol, cultural ties to neighborhood, weak personal and social networks, “wishful thinking”, past experiences, fears of robbery or looting, and the “normalcy bias” (Trainor et. al 2006). Trainor et. al noted that “wishful thinking,” past experiences, and the “normalcy bias” were the top three reasons among his interviewees for choosing to stay in New Orleans (2006). “Wishful thinking” is what Trainor et. al defines as a psychological phenomenon people undergo during times of imminent threat in which they hope or pray that a natural hazard will redirect its course and not cause harm to themselves or personal property (2006). This mindset was a common problem among non-evacuees during Hurricane Katrina, placing them at greater risk than those who chose to heed the public warnings (Trainor et. al 2006). Similarly, the “normalcy bias” kept people from leaving; this occurs when people feel as though emergencies are a routine, everyday occurrence and they should simply go on with their normal activities (Trainor et. al 2006). The “normalcy bias” occurs in many emergency situations as a coping mechanism for those who do not trust in warning systems or the organization managing warnings (Trainor et. al 2006).

            Trainor and his fellow researchers also discovered that past experiences with disasters impacted people’s decisions to stay (2006). Many of the non-evacuees had lived through Hurricane Camille in 1969; with Katrina being downgraded from a Category Five to a Category Three, they felt as though they could handle a weaker storm (Trainor et. al 2006). Past experiences often affect people’s behavior before, during, and after a disaster (Cutter and Emrich 2006); decisions that place them in greater danger are justified through the rationale that they have lived through a disaster before, so they can survive the next one (Trainor et. al 2006).

            Lastly, Freudenburg et. al poses the idea that the overall concentration of populations should be considered when assessing the social vulnerabilities of the New Orleans populous (2008). In New Orleans, there was a large clustering of people in a high hazard region. This clustered effect is what Freudenburg et. al notes as setting the stage for the catastrophe in the first place (2008). If the population had not been so concentrated in a region renowned for its hurricane activity, Katrina would not have impacted so many lives (Freudenburg et. al 2008).

            While different studies may suggest that certain characteristics outweighed others in terms of the capability of the New Orleans populous to plan, respond, and recover from Hurricane Katrina, the researchers all suggest that in most circumstances there was a multiplicity of social vulnerabilities that inhibited the application of survival techniques. Rather than there being one, dominating social vulnerability that dictated the nature of victimization, all factors interplay with one another creating an extremely vulnerable population in New Orleans. The academics mentioned above also suggest that not enough research has been done on social vulnerabilities and cite a need to prevent “tragedies” like Katrina from repeating (Freudenburg et. al 2008, p. 1029). Cutter and Emrich disapprove of “broad-brush approaches” that create overarching formulas for addressing the social vulnerability issue. Instead they suggest individual and community level based planning that assesses who has the greatest need (2006, p. 112).

            In sum, it is important to show that the citizens of New Orleans exhibited social vulnerabilities before Katrina struck, because these vulnerabilities were amplified during and after the storm. New Orleanians were unable to prepare for the storm due to these social vulnerabilities, and therefore were unable to defend themselves against the rising waters, resulting in a shocking death toll (Gall 2011). Furthermore, the social vulnerabilities that impeded evacuation of the residents of southeastern Louisiana were heightened because the piecemeal hurricane protection system and the diminished natural environment were unable to protect them.


Future Mitigation and Conclusions

            Three major reasons for the extent of destruction caused by Hurricane Katrina have been identified: piecemeal construction of the hurricane protection network, wetland loss, and elevated levels of social inequalities. These three factors contributed to the loss of over 1,500 lives, widespread damage, and the extreme financial burdens of recovery. There are many arguments that try to explain the devastation of Hurricane Katrina: government initiatives failed at nearly all levels (local, state, federal), FEMA lacked proper decision-making skills and capable upper-management personnel, or that too much emphasis within emergency management had been redirected to terrorism since the terrorist attacks on September 11, creating confusion in terms of protocol and policies. However, these critiques blame the storm’s devastation on short-term factors that emerged as a result of the storm. The reasons for disaster presented in this paper are long-term, preexisting conditions that created an environment vulnerable to Katrina’s power. Therefore, these preexisting conditions require mitigation efforts to lower the probability of another Katrina-like event.

            By utilizing a tool developed by FEMA known as “STAPLEE” I have analyzed several potential ways in which we might lower the probability of another Hurricane Katrina catastrophe from occurring. STAPLEE allows emergency managers to assess the ways in which a proposed hazard mitigation plan is effective or ineffective. STAPLEE stands for social, technical, administrative, political, legal, economic, and environmental – the areas of society that would be affected by the mitigation plan. Social refers to community acceptance; technical refers to feasibility of a mitigation goal; administrative refers to capable staffing and allocation of funding; political addresses political support; legal looks at  legal limitations and potential challenges to authorities; economic infers costs and benefits of a mitigation plan; and environmental addresses the impacts on surrounding habitats and effects on global environmental goals.

            Based upon the three dimensions of disaster, Table 4 analyzes possible mitigation actions that have been proposed in the wake of Katrina to decrease the loss of life and property in the future. Each action is rated on each of the STAPLEE dimensions based on the history and assessment of the main causes of the Katrina disaster described earlier. Negative (-) symbols indicate an undesirable or impractical condition or outcome and positive (+) symbols indicate a positive condition or outcome; the zero (0) indicates a neutral or indeterminate condition or outcome.










Mitigation Plans


Do Nothing/

Abandon City

(-) Historical significance of city is strong; public outrage would ensue


Getting people out of the city will be a problem; unknown how to decommission a city


Unclear how local government dissolves itself


Heavy political opposition; some support as witnessed after Katrina


Land ownership and compensation will likely cause multiple legal issues


Large economic losses due to loss of major port/ tourist destination


Pollution due to abandoned city not properly managed/



Rebuild to Status Quo


Public will be upset that standards did not improve


Requires same technical operations as the past 40 years


USACE would continue to be in charge of levee construction


Political outcry due to lack of government



Lawsuits likely due to repetition of failed system


High costs for levee system repairs


Continued environmental degradation/ negative ecosystem effects

Levees: Address Engineering Problems/ Fix Height Problems and Different Materials Issues


Public will support improving the levees to benefit their properties and safety


May require removing some levees entirely; could be difficult


USACE would continue to be in charge of levee construction


May create political support for levee revamping


May increase property values with revamped levees


Higher costs due to improved levee building


Continued environmental degradation/ negative ecosystem effects

Levees: Mitigate to Category Five Storm


Public will support improving the levees to benefit their properties and safety


May require removing all levees entirely; could be difficult


Outside staffing needed to assess USACE’s

Cat-5 storm protection


May create political opposition due to tax increases


Will likely cause home displacement and lawsuits over reclaimed land compensation


Extremely high costs due to improved levees; may bankrupt city/ state


Continued environmental degradation/ negative ecosystem effects

Mitigation Plans








Wetlands: Protect Wetlands/ Limit Public Use


Public may support wetland protection; may be discouraged by land use restrictions


Overall limited technical challenges


May need more staff in U.S. Dept. of Fish and Wildlife or local wetland protection offices


Public support for “green” actions taken by government


Land restrictions may cause legal battles; issues with former land use capabilities


Substantial costs due to erecting of barriers/ signs


Environmental benefits due to decreased land disturbance/ possible wetland re-growth

Wetlands: Aggressive Reversal of Wetland Decline


Banned use of public lands will create public outcry


May be difficult to replant wetlands/ facilitate re-growth


May need additional staffing to replant/ monitor wetlands


May be seen as an overly aggressive political move


Restricting land use may cause legal action from oil and gas companies


High costs due to improving wetland regions


Wetland re-growth possible; habitats restored


Increase Community Planning/ Improve Evacuation Plans/Routes


Public will support better evacuation plans and increased focus on poor areas


Not a complex technical task


Need to hire city planners to reassess evacuation routes and community education leaders


Political support for helping the vulnerable


Relatively minimal legal problems


Some cost increases for paying staff members and city planners


Not directly related to environment; may increase pollution from increased use of transportation


Make Vulnerable Populations Only Focus of Hazard Planning


Narrow focus of mitigation likely to upset other members of public


Not a complex technical task


Need to reassign staff; hire experts in social vulnerabilities and emergency management


Political outrage over narrow focus of hazard planning


Law suits over negligent government


Narrow scope of emergency planning may free up money


Environmental issues may be neglected altogether


Table 4: STAPLEE tool assessing potential mitigation plans for the three major dimensions of disaster during Hurricane Katrina. Source: Created by Sarah McKinnell for “Dimensions of Disaster: Landscape, Levees, and the Least Fortunate.” 2012.



            Based upon Table 4, it is evident that the remedies to the piecemeal levee construction, wetland decline, and social vulnerabilities are complex. Utilizing STAPLEE as an assessment tool, however, can aid in deciding the next best steps for mitigation in New Orleans and in other coastal regions. Choosing to abandon the city and do nothing in response to the levee failure had negative results in every category of STAPLEE, indicating that this solution should not be implemented. Rebuilding the levee systems to the pre-Katrina standards had similar results, suggesting that this mitigation plan would be ultimately ineffective. Rebuilding the hurricane protection system to withstand a Category Five storm also produced negative effects. Although it would more than likely receive public approval so that there is not a Katrina-repeat, the feasibility of this endeavor could potentially bankrupt New Orleans, the state of Louisiana, and the USACE.

            Addressing the previous engineering faults, however, may yield constructive results. Creating a unified, reliable hurricane protection system with conformity in construction materials, equivalent heights throughout, and constructed by a singular organization may provide viable hurricane protection throughout the New Orleans region. Cost increases can be expected, along with an increased difficulty in the technical engineering of the levees, but overall the public would support levee improvements that do not result in significant tax increases, as would be expected with redoing the levee system to withstand Category Five hurricanes. In addition, legal complications would be minimal and property values may even increase in New Orleans due to enhanced storm protection. 

            Wetland decline would best be mitigated over a long-term time scale. By limiting public use of highly vulnerable wetlands and attempting to reconstruct wetland habitats, improvements may be seen over time; however, other factors play a role in wetland decline, such as land subsidence, which could hinder the wetland reclamation process altogether. Overly-aggressive actions that bar people access to job sites and recreational activities would more than likely damage the economy, have little political support, and bring about technical implication issues. Similarly, too much emphasis on populations with high social vulnerabilities may hinder New Orleans’ overall ability to react to disaster, because it neglects other populations that are at-risk as well. Increased community planning may help the most vulnerable populations in New Orleans by preparing them with the knowledge and tools to evacuate the next time a storm comes.

            In conclusion, the mitigation efforts proposed and analyzed with the STAPLEE tool might improve the three preexisting conditions that exacerbated the disaster in 2005. With better community planning and emergency response tools, the people of New Orleans might reduce their social vulnerabilities and be better prepared for the next disaster. Further wetland decline might be prevented and re-growth could result in a more stable landscape. Future damages to infrastructure, property, and people might be prevented with adjustments and improvements made to the previous, piecemeal hurricane protection system. Learning from catastrophes and analyzing the conditions that generated widespread destruction allows mitigation planners, governments, emergency response organizations, engineers, and citizens to improve mitigation strategies and decrease the vulnerabilities of property and people.




            In addition to increased community planning, wetland reclamation efforts, and addressing and improving upon the missteps of previous engineering, mapping can be used as a tool to improve upon these three dimensions of disaster. Through the use of modern mapping, including Geographic Information Systems (GIS), remote sensing, LANDSAT imaging, and more, vulnerable landscapes, levee systems, and populations can be identified and analyzed for future mitigation planning. For example, by combining U.S. Census data with terrain elevation data in a GIS, we can create maps that identify where high-risk populations reside, as well as which groups are more likely to experience flooding because they live below or at-sea-level. With these maps, emergency managers can focus evacuation planning and public awareness outreach on the identified vulnerable communities. This will ensure that when another disaster occurs, these communities may be more capable of defending themselves or be given priority in terms of where resources are allocated.

            Mapping can also be used to show spatial – temporal relationships of the region’s natural habitats. By using LANDSAT imaging and other satellite imagery, we can map wetland decline or growth over time. This will allow emergency planners to identify areas with limited natural storm surge barriers. The USACE can run detailed analyses on storm surge patterns and wetland availability to assess where levees may need to be higher than expected due to a lack of a wetland barrier. Mapping can also be used to monitor levee construction progress. Richardson et. al noted that the USACE used maps that were “more than a decade old” when constructing levees and floodwalls in New Orleans (2008, p 36). This is problematic especially when building a hurricane protection system on a landscape with significant land subsidence. The land surface data may have changed within that decade, creating substandard levees that do not meet height requirements. Similarly, events such as Hurricane Katrina can alter the landscape, entirely removing portions of land and changing local hydrologic systems (NASA 2005). Lastly, mapping can ensure better quality construction if conducted on a routine basis, which would improve the overall hurricane protection system.

            Spatial analysis tools are fundamental to mitigation efforts, and mitigation efforts are essential for disaster resilient societies. With greater and more reliable use of mapping, emergency organizations such as FEMA can have eyes on a hazard zone before disaster strikes. Relationships can be predicted in advance based upon location, specific demographic characteristics, and established defense mechanisms in which people may be more susceptible to loss of life and property. By analyzing previous disasters, like Hurricane Katrina, we become aware of the shortcomings of human and environmental interactions. Wetland decline, piecemeal levee construction, and social vulnerabilities worked together to generate serious shortcomings for the entire New Orleans region. Mapping as a foundational tool for mitigation preparations can decrease these shortcomings and establish a greater understanding of the vulnerabilities all people exhibit in the face of disasters.




American Society of Civil Engineers Hurricane Katrina External Review Panel (ASCE). The New Orleans Hurricane Protection System: What Went Wrong and Why. Virginia: American Society of Civil Engineers, 2007.

Blake, Eric S., Christopher W. Landsea, and Ethan J. Gibney. “The Deadliest, Costliest, and Most           Intense United States Tropical Cyclones from 1851 to 2000” National Oceanic and Atmospheric Adminstration, NOAA Technical Memorandum NWS NHC-6. 2011.

Coastal Wetlands Planning, Protection, and Restoration Act (CWPPRA). "The Mississippi River Delta Basin." USGS National Wetlands Research Center. Accessed October 3, 2012.     http://lacoast.gov/new/about/basin_data/.

___.“The Pontchartain Basin.” USGS National Wetlands Research Center. Accessed October 3,   2012.http://lacoast.gov/new/about/basin_data/po/default.aspx

Cutter, Susan L., and Christopher T. Emrich. "Moral Hazard, Social Catastrophe: The Changing Face      of Vulnerability along the Hurricane Coasts."Learning from catastrophe: quick response             research in the wake of Hurricane Katrina. Boulder, Colo.: Institute of Behavioral Science,             University of Colorado at Boulder, 2006. 102-112. Print.

Freudenburg, William, Robert Gramling, Shirley Laska, and Kai Erikson. "Organizing Hazards,     Engineering Disasters? Improving the Recognition of Political-Economic Factors in the       Creation of Disasters." Social Forces 87.2 (2008): 1015-1030. Print.

Gall, Melanie. “Social Dynamics of Unnatural Disasters: Parallels between Hurricane Katrina and the      2003 European Heat Wave.” In Dynamics of Disaster: Lessons on Risk, Response, and     Recovery, edited by Rachel Dowty and Barbara L. Allen, 159-168. Washington D.C.:        Earthscan, 2011.

Graumann, Axel, Tamara Houston, Jay Lawrimore, David Levinson, Neal Lott, Sam McCown, Scott       Stephens, and David Wuertz. 2006. Hurricane Katrina, A Climatological Perspective.           NOAA’s National Climatic Data Center Technical Report 2005-01. Asheville, NC: U.S.     Department of Commerce NOAA/ NESDIS.

Johnson, David L. 2006. Service Assessment: Hurricane Katrina August 21-31, 2005.NOAA’s     National Weather Service. Silver Spring, MD: U.S. Department of Commerce      NOAA/NWS.

Kindinger, Jack L.. USGS, "Holocene Geologic Framework of Lake Pontchartrain Basin and Lakes of       Southeastern Louisiana." Last modified October 17, 2001. Accessed September 18, 2012.       pubs.usgs.gov/of/1998/of98-805/html/kindingr.htm.

Kosovich, John J., State of Louisiana – Highlighting Low-Lying Areas Derived from USGS Digital          Elevation Data . 1:700,000. Map 3049. Washington, D.C.: USGS, 2008.

Miller, DeMond Shondell, and Jason David Rivera. Hurricane Katrina and the redefinition of       landscape. Lanham: Lexington Books, 2008.

Moreau, David. "Levees and Land Use: The Making of a Disaster in New Orleans." InLearning from      catastrophe: quick response research in the wake of Hurricane Katrina. Boulder, Colo.:            Institute of Behavioral Science, University of Colorado at Boulder, 2006. 11-30.

National Aeronautics and Space Administration (NASA). 2005. “Hurricane Katrina Floods the    Southeastern United States.” NASA Goddard Space Flight Center, New Orleans,   Louisiana. Earth Observatory Terra-MODIS Imagery. Web. (accessed October 1, 2012).

___. "Subsidence in New Orleans." Last modified June 3, 2006. Accessed October 8, 2012.           http://earthobservatory.nasa.gov/IOTD/view.php?id=6623.

National Oceanic and Atmospheric Administration (NOAA). 2006. “Hurricane Katrina Flooding and       Spill Maps.” http://www.katrina.noaa.gov/maps/maps.html (accessed September 19, 2012).

___. 2007. “Hurricane Katrina – Most Destructive Hurricane Ever to Strike the U.S.” NOAA Home        Page – Hurricane Katrina. www.katrina.noaa.gov (accessed September 19, 2012).

___. “Land Cover Data for Hurricane Katrina Impacted Areas.” NOAA Coastal Services Center. http://www.csc.noaa.gov/crs/lca/katrina/ (accessed September 19, 2012).

___. "Mississippi River Flood History 1543-Present." Last modified October 12, 2011. Accessed           October 8, 2012. http://www.srh.noaa.gov/lix/?n=ms_flood_history.

Richardson, Harry Ward, Peter Gordon, and James Elliott Moore. Natural disaster analysis after             Hurricane Katrina: risk assessment, economic impacts and social implications.         Cheltenham, U.K.: Edward Elgar, 2008.

Rogers, J. D. "Development of the New Orleans Flood Protection System Prior to Hurricane        Katrina."Journal of Geotechnical and Geoenvironmental Engineering. (2008): 602-617.            10.1061/(ASCE)1090-0241 (accessed September 19, 2012).

Roth, David. 2010. “Louisiana Hurricane History”. National Weather Service. Camp Springs, MD:          NOAA. http://www.hpc.ncep.noaa.gov/research/lahur.pdf.

Smith, Keith, and David N. Petley. Environmental Hazards: Assessing Risk and Reducing Disaster.        New York: Routledge, 2009.

Trainor, Joseph E., William Donner, and Manuel R. Torres. "There for the Storm: Warning, Response,    and Rescue Among Non-evacuees." In Learning from catastrophe: quick response research   in the wake of Hurricane Katrina. Boulder, Colo.: Institute of Behavioral Science, University of Colorado at Boulder, 2006. 314-320.

United States Army Corps of Engineers (USACE) New Orleans District. 2012. "History of MRGO."     Accessed October 2, 2012. http://www.mrgo.gov/MRGO_History.aspx.

United States Geological Survery Coastal and Marine Geology Program, "Geologic Framework and          Processes of the Lake Pontchartrain Basin." Last modified March 10, 2010. Accessed October 1, 2012. coastal.er.usgs.gov/pontchartrain/.

Van Heerden, Ivor, and Mike Bryan. The storm: what went wrong and why during hurricane Katrina.     New York: Viking, 2006.

Acid Rock Drainage in the Upper Snake River: The Presence of Heavy Metals in a Mineralized Watershed, Garrett Rue

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            This project would not have been possible without a UROP Grant, and Dale Miller’s Environmental Writing class, which was instrumental in teaching the skills necessary. The involvement of Dr. Diane McKnight and her vast experience, encouragement, and insight into the issues made this daunting project seem achievable. The logistical support and consultation of Caitlin Crouch proved invaluable, especially in polishing the design, refinement of testing procedures, and site marking.  A special thank you to fellow Snake River Team members and TV stars Greg Lackey, Neil Stewart, Chris Poeppling, and Ben Miller. Without their patient assistance and involvement, it would have been impossible to collect all the necessary measurements and samples. Furthermore, the valuable addition of Dr. Mark Williams as 2nd Committee Chair was greatly appreciated.  And lastly, thank you to Fred at LEGS for the speedy analysis and additional interpretive assistance. Without the support of all the aforementioned, their previous research and expertise, this project would have never come to fruition.









The coupled environmental impact of acid rock and acid mine drainage is a problem facing countless waterways across the Rocky Mountains.  Here we examine the Snake River watershed, located near the former mining boomtown of Montezuma. Over the three decades, researchers for numerous government agencies, the Institute of Arctic and Alpine Research, and graduate students at the University of Colorado have closely monitored changes here in water chemistry and heavy metal contamination present in its contributing streams, resulting from both over a hundred and fifty years of mining activities and the natural weathering of pyrite-laden rock.

The purpose of this project, funded in large part by an Undergraduate Research Opportunity Grant, is to test the dissolved metals present in the upper Snake River, an undisturbed portion of the reach that is naturally acidified and loaded from both surface and subsurface flow. Augmenting this data are field measurements of stream flow, pH, and total dissolved solids collected at a one-week interval between September 22nd and 28th, 2012. The follow-up lab analysis of samples was performed by the Laboratory for Environmental and Geologic Studies using Inductively Coupled Plasma Mass Spectrometry to determine concentrations of Aluminum, Cadmium, Copper, Iron, Manganese, Sulfate and Zinc present at 15 sites distributed among the Upper Snake; the headwaters, 3 main tributaries and their conflux, and the confluence downstream with the pristine Deer Creek. Certain sites were chose due to availability of water chemistry data going back over 30 years, with others chosen because of their reflection of similar climate conditions at the time of sampling.  By choosing sites which have been heavily studied and measured over a large temporal scale, it is therefore possible to correlate these new results with pre-existing data to draw new conclusion regarding the presence of heavy metals in the upper Snake River as to whether these levels have increased, further enrichment is occurring, and how these change in relation to drivers such as climate.





Chapter 1



The Snake River is located west of the Continental Divide in the Rocky Mountains of central Colorado. A long history of hard-rock mining in the region and its location in the Colorado mineral belt, which supports natural weathering processes, is respectively responsible for the problem of Acid Mine Drainage and Acid Rock Drainage in the Snake River.  The parent material from which these mountains were formed contains high concentrations of the mineral Pyrite. It is often called “fools gold” for it’s shiny resemblance to the real thing and the similar depositional features. But an interesting thing happens when water flows over this mineral. Ferrous iron, sulfate, and sulfuric acid are created through a redox reaction when water and oxygen interact. Bacteria can contribute by catalyzing the reaction, speeding up the rate in which the water becomes acidified. As these acidic waters move through a watershed, in the process coming into contact with other minerals and exposed rocks, they dissolve and mobilize more heavy metals like iron, aluminum, copper, cadmium, iron, and zinc. The following formula shows the reaction where Fe is oxidized and O2 is reduced, which creates as a byproduct ferrous iron, sulfuric acid, and reduces the pH of the water.

2 FeS2 + 7 O2 + 2 H2O à 2 Fe2+ 4 SO42- + 4 H+


This ferrous iron can now be further oxidized into ferric iron by extremophilic bacteria.

                              4 Fe2+ + O2 + 4 H+ à 4 Fe3+ + 2 H2O





These heavy metals can also precipitate out when this acidic water is neutralized with more pristine waters, which are then deposited on the rocks and streambed material of a river. Visually, it looks as if the rocks and river bottom have been painted with metals, be it the chalky silver sheen of aluminum or the red rusting of iron, with continued exposure to air furthering these processes. Due to the decreased solubility of certain metals from rising pH conditions, here we see how ferric iron precipitates out of water as ferric hydroxide to coat the streambed. 

                        4 Fe3+ + 12 H2O à 4 Fe(OH)2 + 12 H+




As more ferric iron is rendered into the stream, it also accelerates the oxidation of other pyrite-bearing minerals from which the water may contact. This highlights a significant increase in hydrogen ions and more sulfuric acid to which pH will further decrease, acting to further the dissolving of metals.

            FeS2 + 14 Fe3+ + H2O à 12 Fe2+ + 2 SO42- + 16 H+


In the case of the Snake River, the problem of reduced pH and metal-enrichment is worsened further by later tributaries such as Peru Creek that are themselves laden with metals because of mine drainage. Where metals such as iron and aluminum precipitate out when pH conditions normalize, others such as zinc remained dissolved in the water column and present a serious challenge in maintaining water quality downstream.

Although the Snake River, along its contributing creeks and streams, has levels of metals that seriously affect stream ecology and biotic life, the nature of its sourcing being both due to natural weathering and the legacy of mining in the area makes it difficult to address. Some of these metal concentrations well exceed limits of toxicity set by the state and mandated federally through the Clean Water Act, particularly zinc; however it is important to note that they present a minor health risk to human beings. The Snake River is only 15 miles long and flows into the larger Blue River, later discharging into the Dillon Reservoir. And even though this reservoir serves as a source of drinking water for Denver, this water becomes so highly diluted and neutralized from other water sources downstream as well as groundwater contribution that it possesses no serious threats to human health. Taking this into account, along with the high projected costs of mine site cleanup, and the metal enrichment already taking place naturally in the upper Snake, it has remained a low priority for state and federal cleanup efforts even though it represents one of the most contaminated watersheds in the state. Even if millions of dollars are spent on addressing even a priority site such as the Pennsylvanian Mine, natural metal loading would still take place and such cleanup may yield marginal results. In this regard, it may never be possible for certain parts of the Snake River to become compliant with clear water standards set by the EPA. 

The Snake River currently cannot support a self-sustaining fish population due to the concentrations of metals proven toxic to aquatic life. The Colorado Department of Wildlife stocks this river periodically, to maintain the indigenous populations; however this is a losing battle due to the coupled impact of acid rock drainage and acid mine drainage on water quality. In an effort to better understand these influences on water quality by ARD and AMD, the Snake River Task Force was founded. This highlights a partnership between the following stakeholders: Colorado Department of Public Health and Environment, EPA, Keystone Ski Resort, the Blue River Watershed Group, and conservation groups such as Trout Unlimited. These partner groups have extensive experience with abandoned mine cleanups.  The focus has centered on understanding the factors that influence water quality, as improvement proves difficult due to murky issues regarding liability as outlined in the Clean Water Act, high costs, and prior failed attempts at mitigation by the Colorado Division of Minerals and Geology in the 1980s. It’s important to again note that even serious reductions in AMD only represent part of the problem; as to date there are no remediation strategies for ARD. Therefore, it is possible that the Snake River will never meet the water quality criteria necessary to support fish and a rich aquatic biota.  




Chapter 2

Site Description


            This particular project, adapted from a previous study completed in 1998 by a partnership between Institute for Arctic and Alpine Research and United States Geological Society, focuses on a 4.55 square mile upper portion of the Snake River that serves as the headwaters for the catchment. The valley floor is largely bog iron ore, with portions of glacial till on the western slope and further down the reach (north). Sedimentary rock known as the Idaho Springs Formation is the predominant material from which the surrounding mountains are composed; however, there are small deposits of Quartz Monazite at the southern most portion of the valley. Silver Plume Granite deposits are also present on the eastern slope, roughly half way down the valley.

Figure 2.1


Study Sites


            There are six tributaries of the upper Snake River; however, only three were flowing beyond a trickle during the time of sampling. This was due to warm temperatures in March, which facilitate an early spring melt, and the above-average snowpack quickly disappearing to leave only 19% of average on May 1st.  These conditions and the summer drought to follow were greatly similar to those to the 2002 diel sampling study performed by Laura Belanger. Due to this, her previously evaluated sites, which were also based off the earlier study (Boyer et al., 1999), were chosen for this project to help correlate results with pre-existing data sets in periods of reduced flow. Measurements for pH, TDS, and temperature were collected at each site as well, in some cases at a temporal interval of one week to highlight any change in stream chemistry. Stream discharge was also measured via pygmy meter at multiple spatial and temporal intervals, to indicate any changes in flow or possible addition contributions by lateral inflow of groundwater.

            At each site, samples were taken from both the Snake River and tributaries 10 meters above the conflux as well as 25 meters below the mixing zone. This was the protocol outlined in previous studies and such distance is necessary to maintain that samples not influenced by overlap of hyporheic zones. Additional samples were  taken from the headwaters (0m) to establish baseline loading and pH of the Upper Snake, as well as at interval sites located at 1875m and 1935m to coincide with previously collected data. Further downstream, at the confluence of the Snake River and Deer Creek, each stream and their confluxes were sampled to better understand how a pristine stream serves to alter the water chemistry and precipitation of metals.

             Figure 2.2

USGS Topographic Map, Montezuma Quadrangle, 1:24000


Site Conditions

            Late September was chosen as the best time for sampling. According to 30 years of USGS stream flow data, this is a period of lowest flow and least contributions of “new” water. In 2012, further exacerbating this trend was an early snowpack melt and dry summer that reduced flows of the Snake River to near-record lows. During times of sampling, the USGS gauge station near Keystone showed relatively similar levels of discharge on between days (9/22 and 9/29) and highlight that flows are well below median daily values over the last 63 years of collection. Using pygmy meter measurements of discharge below the Snake River and Deer Creek, it was possible to correlate these measurements for accuracy with its estimated 20% contribution to the gauge at Keystone (Boyer et al., 1999).


               Figure 2.3






            Sample collection will be done according to the Colorado Department of Public Health and Environment’s methodologies and standards for testing surface water (CDPHE, 2001) along with EPA Method 200.8. Samples were collected in 60ml HDPE plastic containers, with a sample volume of no more than 50ml.  Prior to collection, each container was first bathed overnight in a 3% mixture of above reagent-grade nitric acid in ultra-pure deionized water, followed by two flushes of ultra-pure deionized water, then left to dry. During collection, samples will be acquired through 60ml syringes, with .45 um nylon filters to prevent colloidal or eigencolloids contamination. After collection, samples will be labeled with their respective pH, total dissolved solids, and then acidified with trace-metal-grade nitric acid to a value near or less than 1.5 for laboratory analysis. A field blank was prepared using ultra-pure deionized water, also acidified to the same value, to quantify any further possible contamination from containers or acids used. Samples will then be delivered to the Laboratory for Environmental and Geological Studies for ICP-MS (metals) and IC (sulfate) analysis.

            In-site measurements of pH and total dissolved solids were obtained using Eutech instruments that were calibrated twice daily, and rinsed between sampling. Interval measurements of one week were also made to indicate any significant changes in stream chemistry. Discharge measurements were also made using a USGS Pygmy Meter (model 6205) at the Snake River and Deer Creek confluence on September 22 and 29, and at select points of the Upper Snake on September 29.

            Included in the results/analysis section is historical data from the Boyer diel study completed in July of 1998, particularly because sites for this project were chosen from here to allow for corollary comparison. Due to the low-flow conditions observed prior to this project, certain sites were omitted because of a lack of measureable discharge. More recent studies (Belanger, 2001. Crouch, 2009), which took place during times of similar climate conditions and flow, further focused on certain tributaries of upper Snake River as significant sources of metal loading. Accordingly, discharge measurements were taken at select points above and below site (trib) 2095, a previously identified major source of enrichment, to provide insight into concentration and subsequent dilution of solute metals in terms of mass balance. However, due to changing lateral inflow of groundwater at this site and only a single discharge measurement, these mass loads were highly inaccurate when compared to concentrations observed with ICP-MS analysis. Due to more accurate discharge measurements, which were corollary at 20% of that recorded by the USGS gauge station at Keystone, mass loads were instead calculated for sites SN-2 and SN-3, which lie above and below the confluence with Deer Creek. The following equation was used for calculating actual mass metal loads per unit time (sec) at a particular site.

Mx = QxCx


This equation was used to estimate mass loads using known values for discharge and concentrations of metals above the sites of confluence, and was also rearranged algebraically to solve for estimated concentrations above the confluence using observed concentrations from below. 


                        (CaboveQabove) + (CtribQtrib)/ Qbelow = Cbelow




• 9/22: Collect initial pH, TDS, and discharge measurements, as well as samples from select sites.


• 9/29: Collect primary samples from 13 sites, as well as auxiliary measurements of pH, TDS, and discharge to quantify any change in stream flow or chemistry from previous week.


• 9/30: acidify samples, catalog data, and deliver samples to LEGS


• 10/13: Collect secondary pH and TDS measurements from select sites



Chapter 3

Literature Review


The purpose of this project is to better understand the metals present in the contributing streams of the Snake River. Through the testing of 4 sites within the Upper Snake, collecting samples at the confluences of contributing streams and their respective tributaries, concentrations and sources of metal loading can be evaluated.  In particular, where smaller streams conflux with one another and how their heavy metal concentrations change relative to water volume (discharge).  By also collecting field measurements of pH, TDS, and temperature at time of sampling, it can be further understood how water chemistry changes throughout this upper portion of the river and which tributaries are most influential. It is through the establishment of these baseline levels of metal loading present at the headwaters of the Snake River that a standard of water quality can be created in which to evaluate other sources of contamination such as acid mine drainage, which has a significant role in this watershed.

            The compounding of acid rock drainage with acid mine drainage has served to worsen water quality in areas such as the Snake River watershed. This is certainly the case for other places located in the Colorado mineral belt; in the town of Silverton both processes are also serving to exacerbate the levels of metals that are discharging into streams. As a result, 3 out of 4 indigenous fish species have disappeared from portions of the Upper Animas River (Church et al., 2000). To a lesser degree, this is also the case for the Snake River and the coupled worsening of water quality due to these two factors. However, because ground waters in the Snake River area percolate through bedrock rich in conservative elements, and because multiple high-order streams such as the North Forks and Deer Creek are relatively pristine, acid drainage tend to be neutralized and diluted further down the catchment.

            Long-term data sets of precipitation, temperature, and river discharge at many sites throughout the Colorado Rockies show decreasing trends in summer flows (Rood et al., 2008). These correlate to other, more recent findings, which highlight a snowpack that is melting 2-3 weeks earlier (Clow, D. 2010). Using snow water equivalent measurements from SNOTEL sites nearest to the Snake River, a trend was shown between advancement of peak stream flow by an earlier melt season and rising metal concentrations in summer months (Todd et al., 2012). A thirty-year water chemistry data set from the upper Snake River further shows that fluctuations from 100-400% of baseline are occurring during these low-flow months. However, these increases cannot simply be explained by shifting snowmelt timing or by decreased dilution from reduced discharge. It has been postulated that increasing temperatures observed in the Rockies over the last few decades could affect the rates of oxidation of sulfide minerals, but there is uncertainty that this can account for such drastic increases in metals. The coupled influence of all these factors, including their relation to dropping water tables due to reduced recharge of groundwater, and how there is more exposed rock because of reduced snow cover and duration, which also increases rates of weathering, are all explicitly linked and appear to be driven by changes in climate.

            Between 2001 and 2005, a study was done to deduce the quality of groundwater prior to mining at an active site near Red River, New Mexico. An un-mined catchment nearby was also evaluated to provide an analogous idea as to the groundwater composition. It was discovered that two types of water are dominant here, which related to their overlying geology and location. The headwaters of the Red River are fed by springs buffered by conservative elements such as carbonate, keeping groundwater pH around 7.5-8.5.  At middle and lower portions of the Red River, it was found that the water chemistry was vastly different and altered by acid drainage and mineralized water discharging into these lower reaches both above and alongside the mine site. Similar to the Snake River, these acid mineralized waters were formed from debris created by weathering and rapid erosion of pyrite-bearing minerals. Also observed at the site was how rainstorms had large impacts and alterations on the water chemistry of the Red River. This was further confirmed by later analysis of BLM historical data between 1982-1985. The increase in discharge in the spring due to snowmelt served to dilute solutes present in the river, with their concentration continually rising through the dry season until the next snowmelt. If a lackluster snowpack occurred, and no definitive peak in spring discharge, these concentrations continued to rise. Rainstorms in the summer served to slightly dilute these mineralized water systems, but more importantly it was observed that heavy rains actually reversed this diluting trend to create a drastic increase in metal concentrations such as zinc and a profound drop in pH from roughly 7.8 to 3.8. Here we see a flushing effect from an extreme rainfall event, with materials effloresced from evaporation due to prolonged drought being washed into the river. Another interesting observation was that the highest levels of metals and sulfate in the Red River occurred during an intense rainstorm in the valley, where no mining activities take place. This highlights that natural acid rock drainage can serve to alter water quality just as severely, if not more, than acid mine drainage. This becomes an important acknowledgement when we look to understand water quality in areas with high amounts of exposed sulfate-bearing minerals that have undergone mining actives, as well as how changes in precipitation frequency and intensity can serve to alter water quality.

            In the context of these examples of ARD and AMD from differing areas across the US, the aforementioned author of the study, D. Kirk Nordstrom, translated these processes within the context of available long-term climate data and hydrologic change. Particularly troubling was that in 2009 the western U.S. experienced an increase in average temperature upwards to 70% higher than that of the global average. These changes were analyzed in relation to such influencing factors as the Pacific Decadal Oscillation (PDO), El Nino Southern Oscillation (ENSO), North American Monsoon (NAM), and global warming. Though these oscillations all act on differing scales, where ENSO serves to alter weather patterns for a few years and PDO acts on a longer time scale, their combined oscillations can serve to compound the effects of climate change, or help reduce the effects of each other. Careful examination of climate records dating from 1948-2000 in the Sierra Nevada, Rocky, and the Pacific Northwest mountains showed a quickening of snowmelt streamflow timing by 1-4 weeks (Dettinger et al., 1995). This shift in snowmelt has serious consequences in terms of acid rock and mine drainage for the following reasons: it extends the summer dry period, increases the rates of evaporation that leave more residual effloresced salts and decreases the time in which they may accumulate. It is also important to note that in terms of global warming, warmer temperatures have the potential to decrease rainfall frequency and increase the intensity of rains when they do occur. This again has large, looming implications in terms of water quality as it relates to AMD/ARD. As was demonstrated in the data, intense storms had the tendency to reverse the trend of metal concentration dilution and to instead flush higher and higher levels of metals into the studied catchments. Therefore, greater shifts in climate, whether due[DA1] to natural or anthropomorphic causes, have the potential to further mobilize acid rock drainage and worsen its effects by increasing the frequency of these flush-out events. Though not specifically mentioned in this study, recent work has highlighted that a decreasing snowpack, whether due to climate change or not, can further the problem of acid rock drainage because it leaves more exposed, mineral-laden rock to be weathered by less frequent, more intense rainfall events.

            The impact of acid rock and mine drainage on the water quality of the Snake River watershed has led to numerous studies to quantify sources of metal loading and their respective amounts over the last 30 years. In 2001, a grant from the EPA andNational Science Foundation supported an 11-month University of Colorado/INSTAAR project to assess this issue. Across numerous sites in the watershed, sampling was done during periods of high flow (Spring) and low flow (Summer/Fall), in order to observe how heavy metal concentrations changed seasonally. It was observed at most study sites, many of which are shared with this study, that concentrations were at their highest during the summer and decreased as snowmelt contributed to streamflow. Follow-up studies in 2010 evaluated groundwater contributions and subsurface metal loading through tracer analysis in the Upper Snake. More recent research has focused on interpreting long-term data from this area to establish trends in metal loading in relation to influences such as climate change (Crouch, 2011).

The most recent study, done in partnership by the USGS, EPA, and INSTAAR, evaluated increases in metal concentration in the Snake River utilizing the entire 30 years of available water chemistry records, and focused particularly on the influence that climate change may be playing in exacerbating a decrease in water quality. Correlating these large increases in metals with long-term climate, snowpack, and observed hydrologic measurements, a trend can be established between warmer temperatures, decreased stream flow, and earlier shifts in spring melt as having a major influence on a decrease in water quality. Because the study focused on analysis of large temporal and spatial records, as well as combining previous research on changes in Colorado climate (Clow, D. 2010) utilizing similarly comprehensive data, there are valid concerns on how anthropomorphic influences are altering water chemistry and metal concentrations in high alpine streams. Accordingly, as it is estimated that some form of acid rock or acid mine drainage affects over 40% of the headwaters in Colorado rivers and streams (Forhardt, 2003), there are serious implications as to how this may play out in the future. If the trends indicative of this research are indeed correct, then climate change and its influence on the hydrology of the Rocky Mountains are cause for concern. Decreasing water quality not only disrupts biotic communities, disturbs delicate stream ecosystems, and endangers indigenous aquatic species, but can also affect later utilization in terms of recreation, drinking water sourcing, along with other human uses.  

            The inherent variability of factors that drive our climate can serve to exacerbate or reduce the impacts of acid rock drainage, but the problem will not simply go away. The shown variability in metal concentrations has serious implications for both water quality and the ecology of the Snake River. The natural metal-enrichment occurring in the Upper Snake already makes this portion of the stream all but inhabitable for aquatic life. Only a few species of benthic invertebrates are able to survive in such extreme conditions.  Flushing events similar to those documented in New Mexico by Nordstrom are quite possible here, if not inevitable in years of earlier snowmelt and prolonged summer drought. Instances of mass fish kills have already been observed after large flood events in the watershed when sediments and precipitates have washed from primary sources of contamination, such as the Pennsylvania Mine, into Peru Creek which confluences downstream with the Snake River (Berwyn, 2007). There remain portions of the Snake River and Peru Creek that cannot support self-sustaining fish populations, and rely on stock efforts by state wildlife officials to maintain their presence. Zinc concentrations also remain well above clean-water standards.












Chapter 4



Field Observations:


            In an effort to provide a better understanding as to the steady state of water chemistry of the upper Snake River, measurements and sampling were done in a one-week time series. In addition to water sampling, discharge rates, pH, and total dissolved solids measurements were taken throughout the reach as well as the downstream confluence with Deer Creek. All measurements were collected within 2 hours of the time taken the previous week, many within 1 hour, so that any diurnal fluctuations were minimized.

            The headwaters of the Snake, marked as Site 0, showed the highest pH measurements and lowest total dissolved solids. This provided a suitable baseline level and a basis of comparison for observations further down the reach.

            Site 450, above tributary 460, showed slightly more acidic conditions, but only marginal increases in conductivity. Slight precipitation of iron was visually present and water temperatures here were near identical to the previous site, suggesting no additional subsurface inputs. The tributary itself, however, had the second lowest measurements of pH and second highest level of conductivity recorded. Visually reinforcing this data was an entire streambed coated in iron which continued for at least 10 meters below its confluence with the Snake. Below the confluence, at Site 485, we see a rebound of pH and total dissolved solids to levels similar to those above the conflux. 

            Site 900, tributary 915, and the confluence at 940 showed near identical levels of tds, pH, and temperature which continued for a further 1000 meters, as corroborated by readings at sites 1875 and 1935. Iron precipitation was still present throughout this section, although still relatively minor. 

            Previous research from tracer experiments suggested that site 2095 had additional groundwater inputs  (Crouch, 2011). This was also evident in measurements taken by the presence of significant decreases in water temperature and conductivity from a point above the road (a2095) to 25m below (2095b). Differences in pH were also observed, with dilution by groundwater seemingly increasing pH as well as reducing the amount of solids dissolved in solution. Accordingly, iron precipitates were highly visible in the streambed of tributary 2095. Upon mixing with the Snake River (2120), a reduction in acidity occurred and total dissolved solids decreased. Discharge measurements were taken at this site on 9/29 to show how high concentrations with relatively low volume were further diluted by the dominant Snake River flow.

            Further downstream, above the confluence with Deer Creek, the conductivity of the Snake River had increased as well as a slight increase in pH. Iron precipitates were also visually present here. Upon mixing with Deer Creek, a radical change in pH and conductivity occurred. This is likely due to the pristine sourcing of Deer Creek, combined with its high pH and extremely low total dissolved solid. Immediately noticeable at this conflux is a color gradient of orange (iron) and white (aluminum) precipitates. Further downstream, at sample site SN-3, pH increased and conductivity remained at over double that which was present in Deer Creek. The chalky silver coating on the streambed here suggested that aluminum was now the predominant precipitant, with any remaining metals present in solution to likely remain insensitive to low pH conditions. Metal mass balance calculations will be possible with ICP-MS results and discharge measurements to confirm this.


Field Data:


pH & TDS


September 22nd




temp ©

























September 29th




temp ©





















































Snake River above Deer




Deer Creek




Snake River below Conf












        Figure 4.1


        Figure 4.2





















             Figure 4.3













ICP-MS & IC Results


Chapter 5



            The presence of sulfate as a byproduct of the weathering reaction of pyrite serves as an important proxy for determining flow source. Samples were analyzed by LEGS, using Ion Chromatography, providing concentrations present in the solute. In evaluating the data, it is clearly evident that the source of sulfate is in the upper Snake River. Tributaries 460 and 2095, which both had extremely high levels of dissolved metals, show a similar trend in sulfate concentrations. This is indicative of a weathering as well as contact with mineralized material as the water percolates through the subsurface. Water temperatures well below what was observed upstream of these tributaries further hint that lateral inflow was making significant contributions. Of additional interest is how high these concentrations are above that which was measured in 1998, although the higher mean discharge values of July are much greater than those of September. This would hint that as inputs of “new” water decrease, and snowmelt tapers off, sulfate solute concentrations rise to the corresponding lack of dilution occurring.





             Figure 5.1


As previously detailed, the reaction in which sulfate is generated also creates hydrogen ions.  With this established, a clear relation between changes in pH, the rendering anions, and the subsequent dissolving/mobilization of metals is exhibited. Here we see a statistically significant (r2>95%) trend between observed pH and measured sulfate concentrations for both sampling days.  As similar levels were observed at sites tested a week apart, this process would appear relatively intransigent.



            As aluminum is a metal that is sensitive in terms of solubility to pH, we expect to see high concentrations that correlate to observations of low pH along the upper Snake River. Tributary 460, which had high amounts of sulfate present, showed significant levels of dissolved aluminum, at least a four-fold increase from that recorded in 1998. Though again this does not account for differences in discharge that would serve to reduce concentrations through dilution. 

        Figure 5.2.1


Assuming an average water hardness value of 41 mg/L (Boyer et al., 1999) to calculate CDPHE Aquatic Life Standards, it is very clear just how high these aluminum concentrations are in comparison. The logarithmic scaling highlights a difference by nearly 2 orders of magnitude at its highest concentrations. This infers how these concentrations change relative to observed pH, particularly, how pristine inflows such as Deer Creek make drastic reductions in dissolved concentrations of aluminum. Despite reductions, aluminum levels still remain high enough to be acutely toxic to most aquatic species.








  Figure 5.2.2


But if these concentrations are falling with the neutralizing effect of high pH, with pristine waters present beyond the amount needed for dilution to occur, then what explains the significant mass reductions? Using discharge measurements and known concentrations from lab analysis we are able to calculate a mass balance to help explain this. Through a mass load calculation outlined in the methods section, we can empirically solve for the unknown mass load after the confluence of the Snake River with Deer Creek and additionally compare this with the actual observed concentration. As seen in the results, taking into account the dilution occurring by Deer Creek inflow, a significant reduction in dissolved aluminum mass is occurring. This can be attributed to its precipitation from solute due to the rise in pH that makes such high levels no longer soluble. This is also visually evident in this portion of the reach below the confluence, as chalky silver residue coats the streambed.

         Figure 5.2.3




            Cadmium is an extremely toxic metal that is often found in zinc ores. Concentration levels of cadmium observed in upper Snake River were relatively low throughout the headwaters, with notable increases in tributaries as well as below their conflux. The concentrations observed below Trib 940, which extends to Site 2086(m), seemed governed by in-stream processes and chemistry. However, Trib 2095 exhibited a concentration almost 10 times above those observed below Trib 940. When compared to Trib 460, which has similar pH/TDS characteristics and similar trends in metal concentrations, this was still exceedingly high. The differing geology of this tributary is perhaps responsible for the increased loading observed, with granite being the predominate material in which (low pH) groundwater would contact and hence dissolve. 

        Figure 5.3.1


There is an overall lack of definitive information regarding the toxicity of cadmium in terms of an Aquatic Life Standard (EPA, 2001), as there is no testing method known to accurately express this. However, cadmium is regulated and listed as a primary contaminant for EPA Clean Water Standards its concentrations pertain to drinking water. Regardless of water hardness, the maximum levels for cadmium allowed is 5 ppb or 5 ug/L. In the graph below we see that much of the upper Snake is well below this amount with only a slight exceedance at Trib 460. Although further downstream we see that Trib 2095 is well above this amount. But 25m below the conflux these levels are highly diluted and levels of cadmiun concentration fall very near to the standard again. Between Site 2120 and SN-2 further enrichment is occurring. This is perhaps due to the river flowing through a noted iron bog, but again cadmiun levels fall below 5 ppm just after the conflux with the pristine waters of Deer Creek.


              Figure 5.3.2


From the calculated and actual mass loads above and below the confluence with Deer Creek, there are slight differences that would indicate precipitation is occurring. But it’s important to note that due to the variability between calculated loads versus actual loads, this amount could be well less than the 100 ug/s observed.   





      Figure 5.3.3



Concentrations of copper observed through the upper Snake River show a much differing distribution than other heavy metals. Though Trib 460 and 2095 exhibit spikes in concentration. Copper levels are not much higher than measurements taken in 1998, which could again be explained by differences in water inputs, discharge, or dilution. Particularly interesting is that Trib 915, which showed almost no elevated metal concentrations above stream baselines across the panel, is the highest concentration. This tributary shared nearly identical physical characteristics with the Snake River in terms of pH, TDS, and temperature, so this is a peculiar result. This is also indicative of surface in-stream loading of metals as there is no indicators of lateral inflow or seepage that are present at other tributaries. 



         Figure 5.4.1


Again, using an average water hardness value of 41 mg/L (Boyer et al., 1999) to calculate CDPHE Aquatic Life Standards for copper, we see that concentrations observed above Trib 915 are actually lower than historical data. This is the only metal to exhibit this trend. This further supports the idea that in-stream processes are the primary enrichment source. Periods of lowest flow and least water inputs, such as September, show an inverse relationship with the levels measured in July of 1998. Trib 2095, a primary loading source of other metals, here shows only slightly increase above 1998 data.  Of further concern is how elevated copper levels remain through the remainder of the reach, exceeding acute toxicity levels even below the confluence with Deer Creek.





             Figure 5.4.2


From computing the mass loads, there is evidence of precipitation occurring. Though we again see a variation between calculated and actual measurement, so the amount is likely well less than the .8 mg/s. 

       Figure 5.4.3




            As iron is implicit in the creation of acid rock drainage, we can draw similar conclusions to its concentration as proxy for pyrite weathering. Throughout the upper Snake River, it appears that iron concentrations are well above historical data. Similar to copper, this can be possibly explained by periods of decreased flow, such as September, having less water inputs to dilute. But because 2012 had a premature snowmelt this could have additionally exposed more (pyrite-laden) rock sooner than normal, therefore increasing the rates of weathering. Trib 460 shows an extremely high level of dissolved iron, much higher than that observed elsewhere, which was very visually evident for there was a reddish rust coating on the streambed of both the entire tributary and 25m downstream from the confluence where the sample was collected. The peaks in concentration at Trib 460 and 2095 are similar to those of aluminum, although significant variations between 9/22 and 9/29 support the inherent variability of iron concentrations due to photochemical influence at different times of day or different UV conditions (Bencala et al., 1988). Therefore, any conclusion regarding these concentrations when such fluctuations in the data exist are highly dubious.














       Figure 5.5.1


Iron is a difficult metal to evaluate against CDPHE Aquatic Life Standards due to its influence on water hardness and how it is calculated.  But using the average water hardness value of 41 mg/L for the upper Snake River (Boyer et al., 1999) it is still possible to make a basic comparison that for most of the reach concentrations of iron exceeded the 1000ppb (ug/L) standard. However, as similarly observed with aluminum, the solubility of iron is particularly influenced by low pH.














           Figure 5.5.2


The largest discrepancy in mass loads between calculated and observed concentrations for all metals evaluated was with iron. The aforementioned dependence of iron solubility on pH is well demonstrated here by the near 50% reduction in mass load after the pristine inflow of Deer Creek. This subsequent loss of mass from the water column as precipitate could have been eventually remobilized by photochemical reactions that render ferrous iron back into its ferric state, which helps explain the variation and sources of error between calculated and actual loads.









       Figure 5.5.3








Of all the metals evaluated for this project, lead showed one of the most stable concentrations observed throughout the reach. There were no great fluxes or excessive enrichment, but results did exhibit significant fluctuation in measurements between 9/22 and 9/29 at certain cites.



















        Figure 5.6.1



Lead concentrations remained below CDPHE Aquatic Life Standards for nearly the entire reach, only spiking at Trib 2095 and remaining only slightly above the standard until after the conflux with Deer Creek. No mass loads were calculated due to the relatively small concentrations and high inherent sources of error due to data variability. Lead is perhaps the least harmful metal present in the upper Snake River in terms of concentration in relation to discharge, even though it has a low threshold for toxicity.













       Figure 5.6.2






            Manganese did not display much variation in the data along the upper Snake. Tributaries were where the peak concentrations were observed, particularly at site 2095, which was 12x above baseline. This proved well above historical data levels and likely due to low flow conditions reducing dilution.   

















        Figure 5.7.1


Manganese is difficult to evaluate against CDPHE Aquatic Life Standards due to its abundance as a mineral and taking into account how water hardness affects toxicity levels.  By using a water hardness value of 41 mg/L for the upper Snake River (Boyer et al., 1999) the acute toxicity standard of manganese is 1556 ug/L. These levels are exceeded below Trib 2095 and remain so after the confluence with Deer Creek, though only slightly.



















      Figure 5.7.2

Manganese showed very similar calculated and actual concentrations in terms of mass load. It indicates that precipitation could be occurring. However, it is also possible that uptake with sulfate,  to render magnesium sulfate, could help explain this decrease.





















       Figure 5.7.3





The levels of zinc measured throughout the upper Snake River are extremely high. Zinc presents a particular hazard in such high concentrations due to its intransigence to pH. Tributaries seemed to be a primary source; even in those tributaries such as Trib 915 that hinted that water chemistry was dominated by surface flows. Concentrations observed at Trib 2095 were a full order of magnitude above stream baseline levels, which results in a doubling of in-stream amount after its confluence with the upper Snake. Another 50% increase occurred between Site 2120 and SN-2, a trend similarly observed with copper and also perhaps due to flow through more mineralized material.










      Figure 5.8.1


The necessary logarithmic scaling of measurements throughout the upper Snake River makes obvious the exceedingly high concentration of zinc present. Again using the 41 mg/L water hardness average (Boyer et al., 1999), we further see that zinc concentrations exceed acute toxicity levels for aquatic life by at least a full order of magnitude at each site in the reach. For Trib 2095 this proves to be a conservative estimate, as the results show concentration amounts up to two orders of magnitude beyond the standard. This nearly doubles the in-stream concentration below confluence with the Snake. Zinc is a metal of serious concern and a primary limitation in the stream in terms of biotic life. As zinc also demonstrates insensitivity to changes in pH in terms of solubility, this metal is being transported further downstream than any others observed, extending its threat well below the sampling area of this project. 



            Figure 5.8.2


Here we see the intransigence of zinc to pH conditions demonstrated in the mass loads calculated and observed at site SN-2 and SN-3. Of particular interest is how these amounts are nearly identical, inferring that almost no precipitation is occurring and this metal load is remaining in solute well after the additional pristine inflow of Deer Creek. This exemplifies the dangers surrounding the presence of zinc in the water column, especially when accounting for its exceedance of toxicity standards. It also serves to explain why fish stocking is necessary to maintain fish populations; zinc loading at the headwaters of the upper Snake is implicit in making the stream largely uninhabitable.



       Figure 5.8.3



























Chapter 6




            When comparing collected field observations of pH to levels of sulfate observed, a relationship was indicated between increasing concentrations of sulfate and reductions in pH. Both sampling days showed this trend, with high r2 values indicating significant correlation.

              Figure 6.1


            The presence of sulfate is a proxy for pyrite weathering and the rendering of hydrogen ions. This provides additional insight into stream chemistry and dominant processes of metal enrichment occurring. Tributary 915, for example, demonstrated levels of sulfate (and pH conditions) slightly below the Snake River above its confluence, indicating groundwater sourcing. The observed lower temperature of this inflow further supports this hypothesis of groundwater sourcing. Other tributaries with high concentrations of sulfate had corresponding levels of iron, which is implicit in the weathering of pyrite-bearing minerals. However, a statistically valid correlation could not be established between iron and sulfate concentrations. This could be due to fluctuations in observed iron concentrations between 9/22 and 9/29 due to photochemical reactions and precipitate processes.

            All sampled sites did show sulfate concentrations well above historical data, but it is difficult to say exactly what is the cause. It could reflect increased weathering, higher discharge values of the Upper Snake during mid-summer months, or decreased groundwater contributions due to falling water tables from reduced recharge. More recent data would provide greater insight into these changes, allowing for a more conclusive comparison.        



            Metal concentrations did not unilaterally increase when compared to historical data. In the case of copper, the upper portions of the reach had significantly lower levels. For the reductions of copper observed at Trib 460, there were massive increases in other metal concentrations such as aluminum and iron.  High sulfate concentrations further indicate that this is due to weathering byproducts.  Trib 915, on the other hand, showed relatively smaller increases in these metals and drastic increases in copper. Trib 915 shows water chemistry characteristic close to those observed in the Snake, and temperature well below baseline; this suggests that lateral inflow has become the dominant source of water and helps explain the rise in copper concentrations. Since Trib 460 is at a higher elevation, a decreasing water table could have also reduced groundwater contributions to this particular stream. This is supported by a decrease in copper and a rise in metals that are more soluble at a low pH and is indicative of weathering processes. Increased concentration of copper at Trib 2095, a stream with high contributions of lateral inflow, as demonstrated in tracer testing by Caitlin Crouch and evident in observed low water temperatures on sampling days, provides additional evidence of copper and is indicative of groundwater processes.

            Despite results showing metals at extremely high concentrations, such as aluminum and iron, throughout the upper Snake, concentration levels were reduced drastically upon the confluence with the pristine waters of Deer Creek.  Zinc, on the other hand, with similarly high concentrations, remained in solute even after the confluence. This was demonstrated in the mass loads, highlighting both the intransigence of zinc towards pH changes in terms of solubility and the threat it presents to water quality further downstream.

            The concentrations of zinc observed at SN-2 were high and well above average, though less than those taken in 2010. However, when the averaged data from 9/22 and 9/29 was added to the existing available record, a higher statistical correlation value resulted. This provides greater confidence in the findings of previous research that indicated an exponential increase of zinc concentration in the upper Snake River is occurring.    













                           Figure 6.2



            Dsicharges of the Snake River observed on 9/22 and 9/29 were nearly 40% below average than the 63 years of previously collected data. If trends in early snowmelt continue, coupled with increased warming in the Rocky Mountains and reductions in summer precipitation due to climate change, these flows may become the norm. Water table levels will drop accordingly, as they did in 2002, exposing more mineralized material to both weathering and oxidation. The transition from a linear to an exponential increase in zinc concentration observed appeared to be related to these periods of reduced flow, indicating for a future potential of even greater metal-enrichment in the upper Snake. As the river later confluences with Peru Creek, an AMD-impacted stream, this problem will only be enhanced.  

            As evident in observation from this project and those previous, groundwater contributions play a significant role in changing concentrations of certain metals. As recharge is reduced the water table is reduced, and some tributaries may become further dominated by ARD inflows. Massive increases in sulfate, aluminum, iron, and zinc in certain tributaries are already evidence of this when compared against historical data. Greater reductions in stream pH will play a role in rendering waters more soluble to metals and enhancing the transport of metals further downstream.

            When observations from 2012 at Site SN-3 are included with the long-term yearly means from September, the frequency of anomalously low flow years appears to be increasing. If such trends continue, metal concentrations may exceed even exponential increases. The corresponding reductions in pristine inflows that currently serve to dilute these concentrations and neutralize low pH conditions will only serve to compound this.  As a result, environments downstream that are currently marginal for aquatic life will become acutely toxic. This presents a unique challenge to resource managers and stakeholders who must maintain access to clean waters because the Snake River is already on the EPA 303(d) Impaired Waters list. Without the implementation of remediation strategies, currently hampered by outdated provisions of the Clean Water Act, the presence of metals in the Snake River will also remain “in perpetuity”.



                   Figure 6.3



Presence of Rare Earth Metals

            Thanks to the diligent work of Fred in the Laboratory for Environmental and Geologic Studies, the results of ICP-MS analysis show extremely high levels of rare earth metals in Trib 2095. Here the concentrations of Samarium , Neodymium , Uranium, Lanthanum, Gadolinium, Dysprosium, Erbium, Praseodymium, and Terbium were above an order of magnitude of those observed elsewhere in the reach. Considering the extremely low flows of this tributary, this is quite surprising. This site did not correspond with any know surveyed ore or mineral deposits in the area which would explain such high levels, making their occurrence all the more peculiar. As such rare earth metals are just as their name implies, the presence of them into a low-flow, high alpine stream is a topic that merits greater research. Tracer and isotope testing could possibly provide additional insight, as well as continued sampling of Trib 2095 to determine if these levels are rising. 




















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Biogas Emissions and Bioenergy Potential from a Palm Oil Mill Wastewater Treatment System in Southwestern Costa Rica, Hana Fancher 

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The global awareness around sustainable products and practices has accelerated the support for research in developing applied solutions to contemporary climate and energy crises. Biogas capture and recycling technologies are a focus of renewable energy research efforts as they minimize climate change impacts and produce energy. The focus of this study was to quantify greenhouse gas emissions (GHGs), in particular methane, from palm oil mill wastewater and to evaluate the viability of using the emissions as a potential energy source at a palm oil mill in southwestern Costa Rica.




Palm oil and palm oil derivatives have a wide variety of uses in products ranging from biodiesel, to soap, to margarine. Demand for palm oil across diverse commercial markets has led to rapid growth of the industry. Oil palm is also the highest yielding of all edible oil crops, producing up to ten times more oil per cultivated area than other major oilseed crops such as soybean and sunflower (Rupani et al. 2010). High yield and high demand have made oil palm a very attractive cash crop, especially for developing nations throughout the tropics. However, rapid development has brought the sustainability of oil palm cultivation and oil production techniques into question.


During the lifecycle of palm oil production, from oil palm cultivation to final palm oil product, there are many sources of waste. Palm oil extraction produces four main biomass waste groups: mesocarp fiber, shell, empty fruit bunches, and organic-rich wastewater—palm oil mill effluent (POME). Untreated POME is considered to be the most environmentally damaging waste product from palm oil production if it is untreated; not only will it eutrify any stream upon discharge, but POME emits large amounts of GHGs during the wastewater treatment process. POME makes up about 52% of the total waste by weight generated from palm oil mills (Rupani et al. 2010) and yet it is the only type of mill waste that is not re-used by the industry. Approximately 5-7.5 tonnes of POME are produced for every 1 tonne of palm oil (Ahmad et al. 2003), specifically the wastewater comes from three main sources along the oil extraction process: clarification (60%), sterilization (36%) and hydrocyclone (4%) units (Ma, 2000). Generally steam is used in each of these unit processes, which causes POME water to be very hot upon entering the wastewater treatment. Raw POME is a viscous, brownish liquid that is acidic and rich in proteins, lipids, and carbohydrates. Other common environmental features of POME are indicated in Table 1.


Table 1

Typical characteristics of POME










Chemical Oxygen Demand (COD)



Total Suspended Solids (TSS)



Total Volatile Solids (TVS)



Oil and Grease



Ammonia-Nitrate (NH3-N



Total Kjeldahl nitrogen (TKN)



Sources: Ma et al. (2000), Ahmad et al.  (2003), Rupani (2010)


The conventional POME treatment method reduces the organic load prior to discharge into natural waterways through a series of open, gravity driven settling lagoons. The lagoon system has some advantages such as low capital cost, low maintenance and operating costs, high efficiency even under variable organic loading rates (OLRs), and reduced chemical oxygen demand (COD) concentrations by up to 97% (Yacob et al.2006). Although there are advantages to using the lagoon system especially in terms of reducing COD, the lagoon system is a carbon hotspot and major biogas producer that has other disadvantages such as lengthy residence times and large land requirements,. Open lagoon systems utilize mostly anaerobic digestion to reduce the organic loads to a safely dischargeable concentration; however, the anaerobic process also releases large volumes of harmful GHGs—carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O).


Methane has become central to climate change and renewable energy research. Methane is an extremely potent GHG having a warming effect 21 times that of carbon dioxide; however, methane can also be captured and used as a renewable energy source. This dichotomy of harmful versus helpful traits makes identifying sources of methane critical to combating climate change and exploiting renewable resources. For this reason methane is the focus of our research; however, CO2 and N2O are analyzed equally as all of the gases are needed to fully understand biogas production. Table 2 identifies typical feedstock sources of methane with corresponding organic concentrations represented via COD.  




Table 2

COD and methane emissions from various feedstock common in tropical regions

Feedstock Source

COD Range


Average Methane Yield (m3/kg volatile solids)

Palm Oil Mill Effluent

50 – 150


Pig Manure

30 – 90


Dairy Manure

18 – 48


Sugar Beat

1.5 – 5.5


Municipal Solid Waste

15 – 50


Sources: Lam and Lee et al2011, Amon et al. 2007, Chynoweth et al. 1993, Forster-Carneiro et al. 2007; Kabouris et al. 2009, Møller et al. 2004.


There is a statistically significant and positive correlation between COD and average methane yield. Compared to typical feedstock in the tropics, POME contains among the highest concentrations of COD as well as a methane yield. The primary question motivating this research was, “Could this methane yield be captured and transformed into a viable bioenergy or biofuel source?” The goal of our research was to conduct an incubation experiment in order to measure biogas emission rates, patterns, and composition at a typical POME treatment system. Secondarily, we were interested in investigating the role of environmental and biogeochemical controls on the biogas production within our experiments.  




Study Site


This research was conducted at a cooperative palm oil mill located in the Coto Sur Valley of southern Costa Rica (Figure 1). This area of Costa Rica receives an average of 350 mm/month of rainfall for eight months (April through November) of the year, and for the other four months (December through March) receives an average of 100 mm/month (The World Bank Group Climate Portal 2012). Although this may seem a dramatic precipitation difference, seasonal dilution effects have not been considered; the rational is as follows. Annual variability in precipitation may dilute POME by 3%-7%. In open lagoons systems, this seasonal difference in POME dilution by precipitation may cause small differences in biogas production rates. Luckily, the implementation of biogas capture would provide a solution for this issue since it would prevent the influx of precipitation.


The oil mill refines fruits cultivated from surrounding oil palm plantations—approximately 10,000 hectares—placing it globally as a mid-sized mill. The mill produces approximately 300 tonnes of crude palm oil (CPO) per day from 2000 tonnes of fresh fruit bunches (FFB). Unlike many of the other oil mills in Costa Rica, our particular site further refines the CPO into other commercial palm oil derivatives such as margarine. As a by-product of palm oil production, the mill generates 1000 cubic meters of organic-rich wastewater each day, which is piped 0.75 km to the effluent treatment lagoons.


Figure 1

POME Treatment System 

Sources: Google Earth


The effluent treatment system is comprised of 13 gravity-fed lagoons connected by a network of concrete lined channels (Figure 1). The system utilizes eight descending elevation levels to drive the flow path, generally having one set of parallel lagoons per elevation level (Figure 1). The total area of the treatment lagoons is approximately 0.03 km2 and the average depth of the treatment lagoons is 3m. Each individual lagoon is at least the size of one-half of a soccer field. The treatment system has a retention time of 50 days. POME treatment begins in cooling lagoons 1.1 and 1.2; Figure 1, and continues (following numerical labeling scheme) through a series of settling lagoons (Figure 1). Along the earlier stages of the flow path, the particulate matter begins to settle and accumulate on the base of lagoons 1.1-4; however, after lagoon 4, all fine sediment has settled out. At the outlet of lagoon 8 the COD of the POME has been reduced to a regulatory standard of 300 mg/L or below and is discharged into a stream adjacent to the treatment complex. To promote COD removal, the palm oil mill operators periodically add slurries of yeast and molasses in the channel between treatment lagoons 1.2 and 2.1 (Figure 1).


Sample Collection


We collected samples from treatment lagoons 1-6 and 8 on February 29, March 1, and March 2, 2012. We used a sampling rod fashioned out of 3m x 15cm PVC pipe to collect sediment and water samples. In order to capture the spatial variability within treatment lagoons, we collected composite samples of sediment and water from multiple locations within a lagoon and duplicate lagoons when applicable (e.g., lagoons 1.1 and 1.2). Sediment-water slurries were strained through a 263µm sieve into a bucket, and material left in the sieve was homogenized and then used as sediment for the incubation experiments. We preserved aliquots of sediment on ice in the field for downstream analyses. Thereafter sediments were frozen at -20°C. Sub-samples of lagoon water were filtered at 0.22µm in the field immediately after collection, and were stored at 4°C.


Incubation Preparation


We performed two types of incubation experiments: water-only incubations and sediment-water incubations. To constrain fluxes of CH4, CO2 and N2O from POME lagoons each day (three days) we conducted four replicates per incubation type, per lagoon. At the end of the study, 132 incubation experiments had been performed. Water-only incubations were prepared by adding approximately 60ml of the composite water samples to four replicate 125ml glass serum vials. To prepare the sediment-slurry incubations we added an average of 18g of homogenized sediment to four replicate incubation vials, and then we added 60ml of the composite water samples. After anaerobically sealing each vial, we purged the sample with dinitrogen (N2) gas for 2 minutes at 4psi in order to purge incubations of any remaining oxygen in the water or headspace.


Gas sampling


We sampled the headspaces of each incubation vial at four time intervals over the course of nine hours. We collected the first sample of headspace gas 30 minutes after the conclusion of flushing the headspace with N2 gas (sampling time point t0). Our next headspace samples were collected 3.5hrs, 6hrs and 9hrs after t0. We inserted each headspace gas sample into 20ml serum vials flushed with ultrahigh purity, helium-flushed sealed with butyl rubber stoppers (Bellco Glass, Vineland, NJ, USA). Over the course of 3 days, we collected headspace gas samples at four time points for each of the 132 incubation vials; approximately 528 gas samples were transported back to the University of Colorado for analysis.


Gas Analysis


We used a gas chromatograph (GC) equipped with a thermal conductivity detector, an electron capture detector, and a flame ionization detector to analyze concentrations of CH4, CO2 and N2O in sample vials (Shimadzu Scientific Instruments, Columbia, MD, USA). CH4, CO2 and N2O flux rates were calculated for each incubation vial over time points 0 and 6; we saw no increase in concentration after t6 so fluxes were only calculated using the first three data time points (t0, t3.5, t6); the nine hour time point was not included in the analysis. Further discussion of the gas concentration plateau after t6 is provided in the results section.


Aqueous Chemistry


The chemical oxygen demand (COD) of water samples collected from lagoons 1-6 and 8 was determined using Hach Method 8000—Standard U.S. EPA Reactor Digestion method adopted from Standard Methods for the Examination of Water and Wastewater. The total suspended solids (TSS) of water samples were determined in accordance to methodology outlines in Standard Methods for the Examination of Water and Wastewater, (Eaton 2005). The total dissolved organic carbon and total dissolved nitrogen in lagoon samples were analyzed on a Shimadzu TOC-V CSN Total Organic Carbon Analyzer, and nitrate concentrations were determined with a Lachat QuikChem 8500 Flow Injection Analyzer at the Kiowa Environmental Chemistry Laboratory at the University of Colorado.


Gas Data analyses

Gas fluxes were determined from the Shimadzu analyzed concentration data for t0, t3.5,and t6 samples. Detected gas concentrations were determined using the following equation:





                                                                                                                                   Equation 1


Variable: Equation 1


Mass of gas present


Mass of incubated POME slurry


(Concentration of gas)/(headspace injection)

ppm = mg/kg

(Molar mass of gas)/(molar volume of ideal gas)


Volume of incubation bottle headspace


He dilution



Fluxes were calculated for each incubation vial based on linear regression trends. Final t9data points were not included in the flux calculations because our data analysis demonstrated that there was no increase in headspace gas concentrations between t6and t9. Then, the linear regression slope between t0, t3.5, and t6, was used to calculate the gas flux. Fluxes each incubation bottle were then assembled into groups based on corresponding lagoon location and incubation type (e.g. 7 groups for water incubation data, 4 groups from sediment-water incubation data). Any negative production fluxes were then removed from the group (eight fluxes were negative and removed from the group), followed by group mean calculations (µ) and standard deviation calculations (σ), and the calculation of outliers +/- 2σ of the mean. Using Matlab box and whicker Figures A- F were assembled to display group distribution. Outliers are represented as red crosses, the box encompasses data from the 25th and 75th percentiles, and the whiskers extend to the data points not considered outliers.


3.0 Results

Environmental Conditions

In order to understanding the mechanisms, recognize patterns, and investigate controls on biogas production we analyzed the biogeochemical parameters in Table 3.


Table 3

Environmental conditions of POME perLagoon





TSS (mg/L)

COD (mg/L)


(mg C/L)


(mg N/L)

NO3-+NO2-(mg N/L)

































































As expected, temperature, TSS, COD, DOC, and TDN all display descending trends as POME settles and is organic degraded along the treatment system. The alkalinity moves from an acidic influent POME to a neutral discharge. The anaerobic condition of the lagoons is confirmed with dissolved oxygen measurements well below 1.0 (mg/L). For the organic matter to be fully degraded to methane there are several different and important metabolisms at play, all of which are sensitive to available substrates, DO, pH and temperature. In hydrolysis, the first step in organic degradation, lipids, carbohydrates, and proteins substrates are converted into alcohols, fatty acids, amino acids and sugars. During hydrolysis no mineralization of organics occurs so there is no reduction in COD, Eckenfelder (1989). It is likely hydrolysis is occurring in lagoons 1 and 2, and the spike in COD is a result of the addition of yeast and molasses between lagoons 1 and 2 in the connection channel. The yeast and molasses addition is done to increase the rate of the hydrolysis reactions.


Also in lagoon 2 it is probable that the next phase of degradation is occurring; acidogenesis. The fermented bacteria (i.e. added yeast) absorb the hydrolysis products and in turn produce a variety of by-products depending on the starting substrate. Most desirable for methanogens is the production of acetic acidic, but a large portion of fermenters also produce carbon dioxide. Based on site observation and figure 3, lagoon 2 has the highest rate of CO2 production and fermenting occurring. It is important to note that with such a large volume and slow flow rate it is possible to have multiple pathways coexisting such as hydrolyzing organisms and acidogenesis coexisting. Having the coexistence of multiple organisms in one lagoon is a problem that leads lagoon 2 to the most productive lagoon in the system. To account for the large percentage of methane being released from lagoon two and beyond methanogenisis must be occurring. 


The final step in methanogenisis is the conversion of acetogens by-products to methane. Some bacteria will utilize the organic products such as propanol, butanol, acetate, H2and sometimes CO2 to create methane. This step is happening in all lagoons but primarily between lagoons 2 and 4. This leaves lagoons 5-8 for speculation as to what processes are occurring in the later lagoons. As the dramatic drop in methane coincides with a relative leveling of COD reduction, perhaps the majority of preferable substrate has been used up by the time the POME makes it into lagoon 5.


Magnitude and variation in biogas emissions across the lagoons


Figures 2 and 3 show biogas emission rates and compositions for the lagoon system, each of which is comprised of 2 types of incubation data. Fig 2 A-C and Fig 3 A represent data collected from lagoon sediment-water incubations; Fig 2 D-F and Fig 3 B represent data collected from lagoon water-only incubations. Lagoons 2 and 3 were found to be the largest producers of biogas. Maximum biogas production occurred in lagoon 2 sediment-water incubations at approximately 0.50 (mg) of CH4 per incubated slurry (g) per day (Fig. 2 A). Carbon dioxide rates also peaked in lagoon 2 sediment-water incubations with an average production of 0.63 (mg) CO2 per incubated slurry (g) per day (Fig 2B). The production rate of both methane and carbon dioxide begins to decline after lagoon 2; however, in lagoon 3 of the sediment-water incubations, the majority of the biogas mixture emitted is comprised of methane with 64% (Fig 4). This is the only lagoon (for either incubation method) in which methane content dominates carbon dioxide.   







Figure 2

Gas fluxes per lagoon, A-C represent data collected from lagoon sediment-water incubations; D-F represent data collected from lagoon water incubations only

The average composition of methane gas found for the system was approximately 39% and ranged from 2% to 65% across lagoons. The average composition is similar to the findings of Yacob et al. and Shirai 2003; however, both of these studies were performed on open digestions tanks rather than open lagoons: open digestion tanks are the most analogous treatment system to open lagoons. Commonly referenced studies of Yacob et al. (2005), Ma et al. (1999) and Quah and  Gillies (1984) indicate typical methane content of digested POME to be nearly 50%-65%, much of the variability among methane compositions can be attributed to differences in digester type, environmental conditions, chemical properties of POME, and variability in experimental controls (lab versus in-situ studies).







Figure 3

Gas flux compositions per lagoon. Figure 3A represents data from

sediment-water incubations and Figure 3B represent water only incubations

Figure 4

Gas flux composition and Carbon dioxide

 equivalence across the system.


A commonly used parameter for estimating methane emissions is COD. Table 3 shows COD concentrations per lagoon. The untreated, or raw POME, enters the treatment system with a COD of ~32,000 (mg/L), typical raw POME can have a COD as high as 80,000 (mg/L) and on average is approximately 50,000 (mg/L) (Yacob 2005). The average maximum COD of 74,226 (mg/L) was found in Lagoon 2. The highest emission rate is also found in Lagoon 2. The coinciding correlation between methane generation and maximum COD is expected and can be attributed to environment and microbial conditions.  The average methane emitted per lagoon per day is approximately 2,000 kg. Table 3 also displays the biogeochemical characteristics of POME, which strongly determine the rate and composition of biogas emitted.




In this study we found that magnitudes of biogas rates and compositions vary along the flow path. General trends of emission flux data and composition data demonstrated the lagoon system to be front-loaded: the majority of biogas activity and successive substrate degradation occurred in the first half of the treatment process, suggesting that the microbial communities, quantity, and types of substrates present are crucial to the successful digestion of organic matter and biogas production. We determined an average methane composition of 39% comparable to that of Yacob (2006) and Shirai (2003) with 36%. However 39% is lower than an anticipated 50-60%, and significantly lower than the 65% conversion factor adopted by Clean Development Mechanism (CDM) projects (Chong and Philip 2001). This is especially worth noting since CDM projects typically tend to be conservative. The 65% methane concentration has been established using data generated from studies mostly of open tank controlled bioreactor experiments such as in (Ma el al. 1999). Numerous factors have been identified as contributing to this discrepancy between industry estimation and actual measurements: variability in quality and quantity of influent POME due to mill operations, oxygen exposure, pH variation, volatile fatty acids concentration, addition of fermented microbes pushing composition towards CO2, and accuracy of lab versus in-situ measurements.


Despite the discrepancy in gas composition, the biogas production rates we measured indicate high bioenergy potential (Table 4). Presently, biomethane is being emitted into atmosphere, rather than being recycled and used for renewable energy. In an effort to predict the bioenergy potential of the lagoon systems, should these gases be captured calculations, Equations 2 and 3, as well as CDM conversion factors were used to quantify annual methane flux:



Equation 2




Equation 3




Parameters: Equations 2 & 3


Gas emission flux / pond*day


 Incubated gas flux/ incubated POME slurry


Total POME per pond

Power Potential

Est. CH4 emitted/system

Density of 

to kWh (adopted from CDM projects for a methane fermentation capture system)

Composition correction (*CDM assumes a methane composition of 65%, our data produced an average of 39%)



see Table 5

0.66 kg/m3

2.77 MWh/m3


Source: “Engineering Toolbox”,  (Shirai et al. 2003).


Some assumptions made in order to apply the CDM conversion of volume of methane to kilo-watt hours: we assumed our system to be mid-sized and capable of producing 65,000 tonnes of CPO per year. Second, in order for estimates of possible power generation to be made, a closed fermentation system capable of capturing methane must be chosen to replace the existing lagoon system—otherwise no gas will be captured. In this scenario we choose to estimate power production of the system as if the lagoons were replaced with a series of large, closed-tank digesters. Final estimates yielded a potential annual power production range of (11*106  kWh/year)  to (16 *106  kWh/year) from this site alone. This is equivalent to 1-2 power stations capable of producing 500 kW (Shirai et al. 2003).


Table 4

Estimations: Biogas emissions and power potential

Biogas Emission Estimations

Water incubation

Sediment/water incubation

Average CH4 emission rate (per lagoon)

1821 kg/day

4560 kg/day

Average CO2 emission rate (per lagoon)

2423 kg/day

4926 kg/day

Estimated CH4 emitted

(from system)

12750 kg/day

18242 kg/day

Estimated CO2 emitted

(from system)

16963 kg/day

19703 kg/day

Total CO2 equivalent emitted (from system)

Total potential power generated per year (fromsystem)

284712 kg/day


11*106 kWh/year

402794 kg/day


16*106 kWh/year





This study validated the quantity and composition of greenhouse gases being emitted from palm oil wastewater lagoons. The importance of this research is that it will not only increase awareness of untapped energy sources, but it will also hopefully bring applied solutions to other similar situations. Biogas reactors in particular are uniquely beneficial compared to other environmental technologies because of their ability to convert a harmful pollutant into a beneficial energy source. Latin American palm oil plantations and mills soon will need to find energy solutions to become more sustainable to address growing public concerns about the environmental problems of the industry. Costa Rica has recently taken a pledge to become carbon neutral by 2020; POME biogas is an opportunity that could help accelerate this goal. We show that a POME biogas capture system would yield high bioenergy, bringing local socioeconomic and environmental benefits, as well as an overall more sustainable industry. It is important with industries such as palm oil, which are rapidly increasing and do not show signs of slowing, that research and infrastructure be put in place to help them responsibly grow.



 methane bubbles.tiff


Authors Note:


Thank you to all professors, friends, and mentors I have had for the past two years of this projects—the experience has changed my life.













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