Study On Ecological Water Demand And Its Restoring Measurement Of Minqin Oasis In The Lower Reaches Of Shiyanghe River

The basin of the Shiyang River is lack of water resource.At the Minqin oasis of the river lower,the lakes are shrinking and dry,the natural vegetation is withered and died,the process of the land desertification and salinization is speeding up,the groundwater level is dropping,the salinity is increasing,and the ecological degradation is serious.These are threatening the ecological system of the regional safety,and the protection and restoration are imperative.So it is most significant to study Minqin oasis ecological water issues.Firstly,through the status analysis of water demand about the ecological environment at home and abroad,the concept of ecological environment water demand on the Minqin oasis is presented.And the classification and method of ecological water demand is classified.Secondly,the land utilization of the lower reaches of the Shiyang River in Minqin Oasis is analyzed in detail from 1960s to 2001.The results show that the degree of desertification is much more severe than that of oasisment.Ecological water must be provided as soon as possible to rescue the Minqin oasis.The analysis and calculation for the different cases of ecological water demand are as follows.(1)Based on certain ecological protection and recovery goals,integrated with the actual situation in Minqin Oasis,the calculation methods of the ecological water requirements are presented which are fit for the Minqin oasis.In this thesis,the methods of FuBao-pu,Pengman formula and Avermectin diving evaporation model are used to analyze the Minqin oasis ecological water demand.Furthermore,coupled analysis is done for the calculation results of the three methods.It shows that the ecological water demand in this area is 1.856×10~8 m~3 at the present,while it will reach 2.716×10~8m~3 by the year 2020.(2)In this paper,ecological groundwater demand and supply are studied,and the computation method for restoring ecological groundwater demand are investigated. Through coupling the groundwater level with the plant in earth surface,the evaporation intensity of groundwater per year and the salt quantity accumulation in surface soil,a reasonable up/down limits is determined for the ecological level of underground water.And then the underground ecological water demand is estimated at 29.32×10~8m~3～35.27×10~8m~3 which is for the Minqin oasis restored.On the principle of balancing between the supply and demand,the measures for restoring the underground water in the Minqin oasis are analyzed,and the plan are conducted to prevent further deterioration of the groundwater ecological system.At the end of this paper,the strategy and measures that are solved the water crisis in the Minqin oasis have also been discussed.