Research On Groundwater Exploitation Scheme In Desert Area,Case Study Of Pishan River Basin

It is characteristic of criss-cross distribution between oasis and desert, whichare two confronting aspects of arid eco-system in desert area. The regulating andcontrolling role of ecology of groundwater is very outstanding in the arid land,especially in the fragile ecology. Groundwater level depth directly determines thevegetation growth, soil water-salt balance and degree of desertification. Ifgroundwater level is too deep, it may result in river running off, vegetationdegradation and desertification. Evapotranspiration and soil salinization wouldintensify if otherwise. So, the key to groundwater exploitation and utilization indesert area is how to control groundwater depth in the reasonable scope. Therefore,on the condition of effective protection and improvement of current situation of ecologicalenvironment, oasis reconstruction in the desert area of Pishan River basin was takenfor example to research the rational exploitation and utilization schemes ofgroundwater, taking water level depth as constraint condition.On the basis of the limited hydro-geological information as well as suppleme-mentary and necessary geophysical exploration, the hydrogeology conceptualmodel and mathematical model of research region were established according togeneralization of hydro-geological conditions and systematic analysis of thecharacteristics of aquifer distribution and groundwater circulation. Then， themathematical model was identified with water level dynamic observation data, inorder to simulate and predict the change of groundwater flow field under theconditions of development and utilization.In order to ensure the growth of Tamarisk which is the most importantecological protection barrier in the region, and prevent the saltwater intrusion anddesert retreat, there were six groundwater exploitation schemes had been developed,considering mining well space layout and irrigation regression infiltration, andforecasted the groundwater flow field of different schemes in the next twenty years.Compared with uniform wells and no irrigation infiltration, the scheme of unevendistribution of pumping wells in water-rich area and increasing the irrigationintensity near the Tamarisk makes the cone of depression and the drawdown nearthe Tamarisk minimum. It results in the drawdown around6.25m, reduced by2.09m than uniform well,1.05m than no irrigation infiltration. In addition, flood of Pishan river occurs in6~8month, and large amounts offlood resource evaporate in desert on account of large flow and shallow river,which make the time of recharge short and water utilization rate low. Engineeringmeasures such as excavation of river and dam could be taken to increase riverrecharge to groundwater, and if the water level elevates1m, recharge increase about18%than the current year.Groundwater recharge, runoff and discharge conditions are the basis of oasiswater resource, and eco-environment is the barrier condition of oasis in oasification.The rational exploitation and utilization scheme is the root of sustainable develop-ment of desert oasis and virtuous circulation of eco-environment.