Influence Of South - To - North Water Diversion Project On Groundwater System In Xishan Area

Beijing is a city of extreme water shortage. The shortage of water resource has become oneof the main factors affecting the urban development in Beijing. Beijing Xishan is an importantwater supply field which has the advantages of great water quality and wealth of water reserves.In recent years, due to the over-exploitation of groundwater in Xishan, problems like continueddropping of groundwater level and depletion of groundwater resources have been occurred.Thankfully,27.4104m3/d water will be assigned to Xishan to improve the water supply inBeijing, with the completion of the middle part of the South-to-North Water Transfer Project inOctober2014. At that circumstance, which strategy should be taken to utilize the water rationally,to achieve the optimal allocation of water resources will be a major concern. With the collectedphysical geography, fundamental geology and hydrogeology materials, the hydrogeologicalcondition is analyzed by combining hydrogeology survey and pumping test in Xishan, then GIStechnology is gathered to for spatial analysis and visualization. The three-dimensional conceptualand mathematical models which are consistent with the actual situation of the study area areestablished base on the classification of the hydrogeology parameters of the Quaternary aquifersand the Ordovician aquifers. By combining with the hydrogeological condition and the collectedborehole, lithology and long-term groundwater level in the research area, three water allocationschemes are designed according to the principle of South-to-North Water Transfer Project.The main contents and conclusions are as follows:The established numerical model is used to predict the variation of underground water flowfield under different schemes, and to identify the response characteristics of underground watercycle. Scheme three is determined as the optimal solution for water distribution by consideringthe variation of groundwater flow field, the rising of groundwater level and the recovery size ofthe Ordovician groundwater capacity. The Scheme three plans that, from2015to2030, the thirdwaterworks and the Yangzhuang waterworks will maintain the mining status quo; the watersource of Machikou will perform a50percent decrease of mining;884×104m3/a of foreign waterwill be recharged in the sand pit in the western suburbs. What is more, all the owned wells ofkarstic water in Haidian, Fengtai and Shijingshan, which are located in the six central districts inthe city, will be replaced. The amount of decentralized exploitation of the Quaternarygroundwater will decrease from6580×104m3to5141×104m3. In the suburb, the owned wells will maintain the mining status quo. Under this plan, the groundwater level in Ordovician will risefrom15to30m,20to30m and5to20m respectively in Shijingshan district, Mentougou districtand Haidian district. The annual average isostatic differential will be666104m3/a. The annualstorage of Ordovician underground water will be restored1361104m3/a approximately. Thedynamic storage capacity of the Ordovician groundwater will be enhanced.