GIS/EM4 - Land-Use GIS Study for Environmental Conservation of Lake Biwa

Land-Use GIS Study for Environmental Conservation
of Lake Biwa

GIS/EM4 No. 135

Kayoko YAMAMOTO
Masahisa NAKAMURA

Abstract

This paper describes a GIS analysis of land use transformation in the Lake Biwa region, Japan. Development of a Lake Biwa environmental information system was initiated in early 1980s as a pioneering attempt in Japan to promote environmental GIS, which resulted in the compilation of "the Lake Biwa Environmental Atlas". It also provided a basis for computational assessment of the magnitude of waste load discharged into Lake Biwa. The conversion of the earlier GIS into more a generalized system took place in the following years for meeting specific policy assessment needs in the fields of forest resource management and urban land use control.
Today, the application of GIS analysis is being expanded to broader environmental policy issues including those pertaining to the assessment of the change in ecosystem value of the coastal land around Lake Biwa.

Keywords

Land Use, Environmental Conservation, Lake Biwa, Ecosystem Restoration, Resource Information System

1.Introduction

Japan's post-war economic achievements owe greatly to the national industrial development policy to convert rural and agricultural lands to urban and semi-urban lands. While implementation of such a policy contributed greatly to enhance regional economic development, it also led to gradual deterioration of land quality in many regions. To facilitate strong public interest today in restoration of ecotone (land-water interface) functions, for example, the analysis of land use transformation becomes quite crucial. This paper describes the procedure and the findings of GIS analysis applied to assess the land use transformation over the past decades in the Lake Biwa region, Japan.

2.Study Area

2-1.Lake Biwa

Lake Biwa is the largest Lake in Japan and presently supplies some 15 million people in four prefectures, Shiga, Kyoto, Osaka and Hyogo with drinking water, making it the single most important source of water in Japan. It is also important from a geographical perspective. It is natural lake born some five million years ago and is therefore geologically one of the oldest lakes in the world.

Lake Biwa occupies one-sixth of Shiga Prefecture, which is located in the middle of Japan's main island, Honshu (Figure1). The climate is temperate, with some variations from the northern section to the southern section of the Lake. The mountains, which from the northern border of the Lake trap more than 100 cm of, snow each winter, as storms come across the Japan Sea from the Siberian Plains. The southern portion of the lake receives much less snow, and can be oppressively hot and humid during the summer. There is a rainy season early each summer (usually lasting from mid-June through mid-July) and a second, less severe period of rain and windstorms each September. The monthly average air temperature and rainfall for Hikone, located midway along the lake' eastern shore, are presented below.

Lake Biwa is 63.5 km long from north to south and is strongly constricted, reaching a minimum width of only 1.35 km about 16 km from its southern end. The main basin north of the constriction is called the North Basin, while the sub-basin south of the constriction is called South Basin. The North Basin has an average water depth of 44 m, but the south Basin is only 3.5 m deep on average.

Figure 1. The Location of Lake Biwa

2-2.The Basin of Lake Biwa

Lake Biwa's drainage basin is surrounded by mountains ranging from several hundred to over 1,000 m above sea level. It is about 5 times the size of the lake itself, and the Shiga Prefectural boundary closely correspond to the basin boundary. Approximately 60% (exclusive of Lake Biwa) of the land area is forest-covered hills and mountains, while 25% is farmland mostly for paddy agriculture. Most of the forest vegetation is pine (pinus densiflora) and mixed deciduous broadleaf. The area surrounding the lake's basin have recently become popular suburbs of the larger cities of Kyoto and Osaka, and there has been a steady increase in population since the mind 1980s.

There are some 460 streams of various size flow into Lake Biwa. The only out-flowing river, the Seta River becomes the Yodo River joined by two other rivers downstream, flows into Osaka Bay. A weir constructed in 1906 at the uppermost end of the Seta controls both the river's flux and the water level of the lake. The lake is a major source of water supply and a popular destination for recreational activities for the downstream residents.

3.Lake Biwa Comprehensive Development Project

The quality of water in lake has been profoundly influenced by the economic development of the 1960s and early 1970s, when the trophic level of the Northern Basin changed from oligotrophic to mesotrophic and that of the Southern Basin from mesotrophic to eutrophic. The lake's biota exhibited corresponding drastic changes; tap water drawn from the lake developed a foul smell caused by certain planktonic algae in 1969; and freshwater red tide caused by the bloom of a fagellate alga, Urogkena americana, first appeared in 1977. These phenomena have recurred every summer since their initial appearances.

Since 1970, the national and local governments have undertaken several projects to prevent and ameliorate pollution of Lake Biwa. In 1970 the national government implemented control of waste water discharge into the lake, slowing europhication considerably. In 1980, the Shiga prefectural government enacted an ordinance entitled, "the Ordinance for the Prevention of Europhication in Lake Biwa", which specified even stricter control of waste water discharge and, for the first time in Japan, prohibited the use of phosphate-containing synthetic detergents.

The Lake Biwa Comprehensive Development was inaugurated in 1972 and completed in 1995 by the national government and the governments of Shiga and the downstream prefectures. The project was concerned with the development and conservation of the lake's water resources, flood control in the drainage basin and along the Yodo River, and the watershed conservation and development. Among the project's specific goals were: (1) to increase the water supply available to the downstream communities by a maximum of 40m3s-1 to meet the increasing demand, (2) to construct a regional wastewater system with advanced treatment to prevent further pollution of the lake's water, and (3) to construct a round-the-lake levy for flood control and for maintaining the stable lake level.

4.Analysis Method

The primary objective of this study was to make a comparative analysis of land use changes in the Lake Biwa watershed between 1965 and 1994. The analysis results have been used to assess the land use transformation and its implications. The analysis system used in this study were ARC/INFO and ArcView.

The GIS functions use in this study are, as shown in Figure 2, as follows:

Processing digital map ARC/INFO; the functions of transforming files and overlay
Analysis of land use ARC/INFO; the functions of spatial analysis and map-making
Presentation ARC/INFO; the function of transforming files, ArcView ; the function of map-presentation

The 1965 and 1994 data mentioned above were developed applying the map-making function of ArcView to the respective topographical and land use maps.

Figure 2. The Process and GIS's Functions

5.Analysis Results

The major findings of the current study include;

Urban encroachment and other land use transformation such as land clearing for golf link development have severely impacted the ecological resource profile of the Southern Basin of Lake Biwa.
Several modes of land transformation over the past decades were identifiable with regard to land use changes from rural and semi-rural uses to urban (urban residential, industrial and commercial) use.
Exploratory assessment was made of the potential gain in value of ecosystem restoration with regard to, for example, increase in self- purification capacity and enhancement in bio-diversity along the coastal land.

The large-scale land transformation began to take place in the Lake Biwa watershed in association with the implementation of LBCDP. While its primary objective was to make available additional 40 m3 of lake water for downstream uses, the associated regional development projects transformed the watershed from the primarily rural and agricultural land to the land dedicated to urban and industrial development with highly mechanized paddy agriculture with extensive irrigation. As a result, the rate of population increase as well as the per capita income in the past decades have become among the highest in the nation.

For countering development impacts on lake environments, a number of conservation policies has been introduced in Shiga Prefecture since. Today, the policy orientation is to restore and realign the ecosystem functions damaged or lost due to the large scale land transformation in the past decades, particularly in connection with implementation of LBCDP.

Figure 3. The Land Use of The Basin of Lake Biwa

Figure 4. The Land Transformation of The Basin of Lake Biwa

6.Conclusion

The final goal of this study is to use the application of GIS analysis in specific environmental policy issues including those pertaining to the assessment of the change in ecosystem value of the coastal land around Lake Biwa. Although the availability of data was limited in this study, it was possible to make some general observation on the land use changes for past thirty years.

Based upon the analysis, it was found that the land use have remarkably changed along the southern coast, suggesting the growing need for better forest resource management and land use control. The current GIS study will have to be further refined and combined with management models to address such policy issues.

References used

Kayoko Yamamoto(1999)A Study on The Land Use Changes on The Basin of Lake Biwa in Shiga Prefecture. Papers on Environmental Information Science NO.13, 239-250

Kayoko Yamamoto et al.(1999)A Study on The Land Use from The Viewpoint of The Properties of The Rivers Basin on The Shore of Lake Biwa in Shiga Prefecture. Lake Biwa Research Institute Bulletin NO.17, 52-61

Jorgrnsen, B.B. et al.(1996)Eutrophication in Coastal Marine Ecosystem. Coastal and Estuarine Studies NO.52, 272p.

Masahisa Nakamura(1999)Lake Biwa and The Asian Environmental Agenda. Integrated Environmental Management, Lewis Publishers�C19-28

Hideji Yokoyama(2000)The Landscape-ecological Approach to Landscape Conservation in Drainage Basin of The Lake Biwa. Journal of Japan Society on Water Environment VOL.23, NO.1, 17-20

Masahisa Nakamura(2000)Toward Transformation of Social Systems Suitable for Achieving Comprehensive Conservation of Lake Environments. Journal of Japan Society on Water Environment VOL.23, NO.1, 21-25

Authors

Kayoko Yamamoto, PH.D, Lake Biwa Research Institute
1-10 Uchidehama Otsu Shiga 520-0806 Japan
Email:yamamoto@lbri.go.jp, Tel: +81-77-526-4800, Fax: +81-77-526-4803.

Masahisa Nakamura Director, Lake Biwa Research Institute
1-10 Uchidehama Otsu Shiga 520-0806 Japan
Email:nakamura@lbri.go.jp, Tel: +81-77-526-4800, Fax: +81-77-526-4803.