Ecological and Environmental Water Requirements for the Weihe River in Shaanxi Province

Weihe River, the largest tributary of Yellow River, is the "Mother River" of Guanzhong region in Shaanxi Province. Its ecological and environmental health directly affects the sustainable development of local society and economy. Aiming at the main problems existing in the ecological and environment of the Weihe River, the EEWR including minimum water requirements for aquicolous biotops maintenance, water requirements for channel seepage, water requirements for channel evaporation, water requirement for stream's self-purification and sediment transportation were estimated in this paper. The instream in Shaanxi reach of the Weihe River is selected in the study; the temporal scale of typical years include P = 25 % (1963), P 50 % ( 1990), P 75 % ( 1982) and P = 90% (1979). The results show that the EEWR for the Weihe River mainly include water requirements for the stream's self-purification and those for sediment transportation. During different typical years, the shortage of EEWR for each river section varies with different extents. From wet year to dry year, the amount of water requirements decreases except that of Linjiacun section. Comparing the EEWR with runoffs, the degree of the water requirement shortage for the Weihe River is serious.