Study On Pattern Of Rational-Utilize And Circle-Change Of The Groundwater In The Inland Basins Of Northwest China

The inland arid area in northwestern China is characterized by a close geographical environment,independent water resources system, scarce water resources and vulnerable environment. In these area,surface-water and groundwater exchange frequently with large amount and therefore is regarded as asingle resource. Much water loss is due to evaporation. Since large amount water was used with therapid extend of irrigation area and the construction of hydraulic engineering in the upper to middlereaches of the rivers during past several decades, oases are withdrawing and the area of landdesertification is expanding. Furthermore, some salt marsh and salt lakes change into salt desert andgroundwater resources are depletion. In addition, local water unbalance between irrigation and drainagein agricultural area cause large area secondary salinization. Thus, on the principle of sustainabledevelopment, the main purpose of this study is to establish rationalization pattern for water resourcesdevelopment and to ensure sustainable development of water resource and eco-environment bydiscussing changes of water resource and eco-environment in condition of natural state and humanactivity.Taken the Heihe River catchment as case study, the present work is firstly to illuminate geographicenvironment and its change on a wide spatial-time range, which controls the changes of water resourcesin this basin and adjacent basins by using results from recent studies. Then focused attention on thechanges of water resources in the Heihe River basin, the changes of precipitation and runoff arediscussed by analyzing the data series from 1940s to 2000s by using the methods of climate statistics,precipitation and stream flow anomaly, residual mass curve, hydrograph separation and spectrumanalyses. Meanwhile, the main hydrogeologic setting, aquifer characteristics, groundwater flow systemand interaction between surface water and groundwater in middle to lower reaches of the river, aredemonstrated in detail on the basis of large number of borehole data, water chemistry and isotopes data.The changes of groundwater recharge in catchment under the conditions of present and differentclimate or runoff are estimated by analogue method using results from numerical groundwater flowmodeling in typical area. The degree and phase of water resources development and the inducedchanges of water resources in middle reaches of the river are further discussed by analyzing thestatistical characteristics of stream discharge difference from the data series of Yingluoxia andZhengyixia station. Based on the above results, the patterns of water resources changes are given out.The suitable water table range for vegetation in oases is quantified according to the previousstudies of groundwater dependent ecosystems. In view of this range and water resources situation inrecharge area under the conditions of performing water resources allocation, level of the per people andthe per infield, ecology and environment water requirements and demand and supply analysis of waterresources, the Heihe River basin is classified into three types area for water resources development andeight subarea. Finally, some measures on rationalization of water resources development in inland aridbasins in northwestern China, are recommended based on the common features established in this study.