Mesh Data Analysis of Watershed Environment Focusing on Land Use and Water Supply-demand

Abstract

This study intended to create the watershed environment database compiled by recalculating some mesh data in the 1990s and the 2010s, and to discuss comparatively regional characteristics of Japanese major 109 river basins by analyzing land use type and water supply-demand estimation of the basins based on the database. Land use type changed in 13 river basins from the 1990s to the 2010s, and the changing patterns varied basin to basin. While both agricultural and residential water demands in Japan as a whole have decreased since the 1990s, some river basins have experienced water demand increase. River basins that experienced the increase of agricultural water demand are located in eastern part of Japan. The increase is not brought about by agricultural area expansion but the increase of water requirement per area. On the other hand, river basins that experienced the increase of residential water demand are located in main urban areas in Hokkaido, Tohoku, Chugoku, and Shikoku Regions. This fact shows that water demand gap between urban area and the surrounding area has expanded. Water supply-demand ratio has great differences among river basins. To manage the stable water supply, despite such regional differences of water balance, one possible solution is the cooperation between a river basin with high water supply-demand ratio and a river basin with low water supply-demand ratio.