The Characteristics and Variation of Precipitation and Water Resource of Sichuan and Chongqing Basin on the Eastern Side of the Plateau
高原东侧川渝盆地降水与水资源特征及变化

Water is an important resource for basic human survival,for ecosystems,and for many key economic activities.In many parts of the world,water already is a scarce resource,and this situation seems certain to worsen as demand increases and water quality deteriorates,even in the absence of climate change.Moreover,most major impacts of climate variability and climate change on water resource are very uncertain.The Sichuan and Chongqing basin lies on the eastern side of the Plateau,and is influenced by many kinds of monsoon,such as tropic monsoon,subtropic monsoon and the Qinghai-Xizang Plateau monsoon,so its climate is complex and especial.At the same time,this region,as a transferring station on the water transport way from the South China Sea and the western Pacific Ocean to Northwest and North China in summer and autumn,plays a great role in the water budget of the areas around.Therefore it is important to study the characteristics and variation of precipitation and water resource of the Sichuan and Chongqing basin.Based on the monthly temperature and precipitation data of 1951-2000 in the Sichuan and Chongqing basin,the characteristics of precipitation and water resource have been analyzed.In this paper,F=P-E,where F denotes water resouce,E is evaporation and P is monthly precipitation.It is found that,the annual total water resouce in the region is 457 mm and mostly distributes in summer that contributes 56 percent to the annual amount in the region,and especially the water resource in July can reach 106.5 mm.In addition,the percents contributed by other three seasons are as follows: 21 percent by spring,21 percent by autumn and 2 percent by winter.So it is clear that the seasonal difference of water resource is obvious in the Sichuan and Chongqing basin.From 1951 to 2000,the precipitation and water resource in the Sichuan and Chongqing basin had decreased and the decrease trend is the most obvious between 1990 and 1997.There is an evident difference of water resource in the eastern and western part of the Sichuan and Chongqing basin.The precipitation and water resource in the western part had decreased during the 50 years,and contrary to the western part,the water resource in the eastern part shows an increased tendency.The descending of the water resouce are mainly influcenced by the decrease of the precipitation in the Sichuan and Chongqing basin,especially by the rainfall in the western part of the basin.The weakeness of northward and westward expansion of the water vapor transport with summer moonsoon has an important influence on the variation of precipitation in the region,and the variation of the precipitation further affects the change of water resource.