Mechanism of Groundwater Replenishment in Ejin Basin

Ejin Basin underlying complex aquifer,lies in the lower reaches of Heihe River with arid climate and 39.8 mm mean annual precipitation.In Ejin Basin,because the balance of natural ecosystem is frangible to upset,it is very important to estimate and to rationally utilize the limited groundwater resources in order to maintain the balance.Water samples were collected from the Heihe River and from wells for chemical and isotopic measurement all over the basin.Piper diagram gives two main types of hydrochemical features.On the background of regional geology,combining isotope δ~(18)O,Tritium and chemical analysis with groundwater flows indicated by shallow groundwater level's contour map,different kinds of groundwater source and how to replenish groundwater were discovered.In the north of the study area,artesian wells get them replenishment from the mountainous area at the boundary between China and Mongolia.Most of the groundwater resources replenishment in Gurinai oasis comes from Heihe River seepage flow by the highly conductive paleochannel,not from Badain Jaran Desert in terms of TDS and Tritium analysis.By radioactive isotope Tritium analysis,different groundwater's ages were approximately estimated,which are younger than 35 years.On such efforts,groundwater resources can be effectively evaluated with the engineering impact of The Heihe River Project.