Beijing Xishan Karst Water Resources Evaluation Can Be Mined

Beijing is a seriously water shortage city,two thirds of whose water usage is groundwater. As the rapidly development of urbanization, imbalace of water supply and demand becomes sharper and sharper.Beijing XiShan is located in the westsorth area of Beijing.XiShan karst-water is the back-up water resource of Beijing for its quantity is large and quality is good. In recent years, the continuous water explotion and water shortages have caused geological environment problems in Xishan areThe level of assessment of water resourse in study area is low, so this paper try to on the basis of field investigation,numerical simulation method and water balance method to evaluate sustainable yield in Xishan area to provide a scientific basis for water resources usage.Discussed karst-water condiction of recharge,runoff and discharge by analysis of groundwater dynamic field,regional geological structure and engineering investigation.The karst-water accepts precipitation in naked karst limostone areas,Yongding River leakage and Dashihe River lateral recharge.Runoff is affected by topography and tectornic structure.Karst-water accepted in Lujiatan area runs from southwest to northeast.Karst-water accepted in Junzhuang area divided into two parts,one part runs along Yongdinghe fault to Babaoshan fault,another part runs along Jiulongshanxiangyu syncline to Wenquan area.Karst-water discharge includes artificial exploitation and recharge upwards.Using numerical simulation method and water balance method evaluate and assess the sustainable yield under the condition of keeping current exploitation,the south-to-north water transfer and emergency exploitation.The result shows:keeping current exploitation will cause geological environmental problems;Decreasing50%percentage exploitationof Shuityansanchang will lead to the rise of water level and the sustainable yield is8100.2×104m3/a;Adding the exploitation of3X104m3/d in Shahe、Changping area has not caused serious influence on water level in the study area and that can work with the emergency exploitation in the region and the sustainable yield is10765.7×104m3/a.