USGS YUKON RIVER STUDIES
DORNBLASER, MARK . USGS.
Striegl, Rob . USGS.
Hooper, Richard . USGS.
Aiken, George . USGS.
Eberl, Dennis . USGS.
Krabbenhoft, David . USGS.
Schuster, Paul . USGS.
Study Objectives: The Yukon River basin covers 330,000 square miles in northwestern Canada and central Alaska, an area greater than Texas (Figure 1). It is one of the largest and most diverse ecosystems in North America, and is of prime importance to the ecology of the Bering Sea, contributing most of its freshwater runoff, sediment load, and dissolved solutes.
The Yukon River basin is changing. Air temperature records between 1961-1990 show a warming trend of about 0.75 degrees C per decade at latitudes where the Yukon River is located. Continued warming will affect permafrost distribution, glacial runoff, and biogeochemical fluxes within and from the basin. The exact effects are unclear. The USGS National Stream Quality Accounting Network (NASQAN) is developing a baseline characterization of water quality conditions in the Yukon Basin that will serve as a benchmark for future studies of the river. In addition, USGS is conducting a variety of process studies in the basin, investigating such topics as the production and utilization of dissolved organic carbon in headwater areas, Hg methylation, water-atmosphere exchange of greenhouse gases, and sediment chemistry.
Study Approach: NASQAN is performing fixed station sampling at five sites during 2001-2005 (Figure 2) to estimate annual mass fluxes. Scientists will also conduct intensive boat-based synoptic samplings to create a broader spatial characterization of the river and it's sub-basins. In addition, lake sediment cores will be analyzed for trends and seasonal input of atmospherically transported contaminants.
Fixed Site Network: The five fixed sites will be sampled for a variety of organic and inorganic constituents over a five year period to establish a baseline database. Each year, these sites will be sampled approximately seven times, including one under-ice measurement. Mass fluxes calculated for the fixed sites will be used to identify source areas of contaminants, and to estimate delivery of these contaminants to the Bering Sea.
Synoptic Sampling: Scientists will conduct intensive boat-based sampling of the Yukon River twice per year, once near peak flow conditions in early June and once near base flow conditions in August/September. The entire Yukon River will be sampled by this method over a three year period. In 2002, sampling will occur through Yukon Flats between Eagle and Stevens Village, Alaska. In 2003, between Stevens Village and Pilot Station. And in 2004, between Whitehorse, Canada, and Eagle, Alaska. The synoptic sampling will increase the interpretability of the flux measurements, and will provide an alternate data set that may be a more sensitive indicator of change.
Figure 1. Figure 1: Location of the Yukon River Basin in Alaska and Canada
Figure 2. Figure 2: Locations of fixed station sites in the Yukon River Basin
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