The Study On Theory And Method Of Ecological Water Demand In The Lower Reaches Of Heihe River

The study of ecological water demand is very important for the shortage of water resources and the severity of ecology degradation and the endanger of ecology safety in the lower reaches of Heihe River. Little efficient precipitation in the lower reaches of Heihe River is supplied to natural vegetations. While its ecosystem is depend on the underground water to maintain the balance. The ecological water demand in the lower reaches of Heihe River includes the water amount to maintain the stability of natural oasis ecosystem and to improve statue of ecoenviroment and protected oasis ecology.Based on the panel of Arc GIS, using the remote sensing image of 1980s' and 2000 year, the degradation tendency of landscape pattern in the lower reaches of Heihe River is analyzed. The study is showed that intensity of desertification is much more than that of oasis. Ecology protection and restoration in the lower reaches of Heihe River is imperative. According to the water resources of study area, the method of special decision-making is applied to set the target of ecology protection and restoration in the lower reaches of Heihe River based on some ensure measures and the scheme of water allocation, the landscape pattern of natural oasis in the lower reaches of Heihe River reaches the scale of the initial of 1980'.According to the target of ecology protection and restoration and considering month as temporal scale, the ecological water demand of natural oasis, of water area and of underground table is analyzed in the area of surface water allocation: The formula of phreatic evaporation model is applied to compute the water demand. The ecological water demands of different targets of ecology protection and restoration of different level yearin the lower reachers of Heihe River are put forward, which provide the scientific gist for rational water resources allocation.