In Hunan Province, water resources is sufficient for agricultural use and the supply is 2 58 times of the demands. But their spatial and temporal distribution varies greatly. Seasonal drought and torrential flood in hilly land, and flood and waterlogging in the plain areas occur frequently. Especially, every year the farmland damaged by drought accounts for over 66 47% of the total area affected by natural disasters. At the same time, the low exploitation and utilization rate of water resources, the potential increase of demands for water in cities and industry may make the water resource more...