北京市玉泉山泉恢复条件研究

A study on recovery condition of Yuquanshan spring in Beijing

西山地区岩溶水是北京重要的供水水源,年均开采量达到1.5×108m3。多年持续过量开采地下水导致了玉泉山泉断流近42年。南水北调来水进京后,有必要考虑调蓄区域含水层系统,恢复玉泉山泉景观。在深入分析区域水文地质条件基础上,结合数值分析方法,研究玉泉山泉恢复条件,取得认识:玉泉山泉的主要补给源为河道入渗补给,占总补给量的74.7%,其次是大气降水补给,其比例为25.3%;为实现玉泉山泉复涌,需要将区域岩溶水开采量从11 290×104m3/a压减至4 282×104m3/a,停采第四系地下水,同时在永定河河道进行人工回灌,回灌量为2×108m3/a;研究发现相对于压采措施,泉的恢复对回灌比较敏感,未来调蓄方案应优先考虑回灌措施。

Xishan karst system is one of the most important wellfields in Beijing which supply an average of 1. 5× 10^8m^3/ a. This over-extraction of groundwater has resulted in regional decline of water levels and the cease of Yuquanshan spring for about 42 years. The South-to-North Water Diversion Project may partly mitigate the issue of water shortage of the study area. We analyze the recovery condition of spring based on the hydrologic analysis and the development of a ground-water flow model. The results demonstrate the major recharge sources for the karst aquifer system are areal recharge of rainfall and infiltration of Yongding River bed which contributed around 74. 7% and 25. 3% of total recharge. In addition,the short-term scenario that provides a recovery for the spring is founded to be by reduce current abstraction of karst system from 11290 × 10^4 to 4282× 10^4m^3/ a,closing the no-public well of quaternary aquifers and implementing the high artificial recharge rates of 2 × 10^8m^3/ a. The recovery of Yuquanshan spring is much more sensitive to variations in recharge than pumpage,which indicates that the management of Xishan karst aquifer system should consider increase artificial recharge to save the spring.