大兴迭隆起隐伏岩溶水资源评价及开采方案预测

The covered karst water resource evaluation and mining plan prediction in Daxing overlapping uplift area

大兴迭隆起地区隐伏岩溶地下水是北京市的重要水源,为保障水源地能持续为大兴、通州地区提供优质的城镇生活用水,需对研究区岩溶地下水进行水资源评价和开采规划预测分析。利用数值模拟法,应用GMS模拟软件对研究区岩溶水系统进行地下水流数值模拟及水位变化预测。建立的岩溶水系统模型分为5层,模拟验证期为12年9个月。由模型评价的岩溶水系统补给资源量为14 425.74×10~4m^3/a,可开采资源量为14 310.52×10~4 m^3/a,其中岩溶含水层可开采量为2 309.36×10~4 m^3/a。在模型识别验证后,分4种开采方案对水源地进行开采预测,通过对典型观测孔水位过程线拟合和研究区水均衡分析可知,按2020年之前维持现状开采,2020年后停采念坛水源地,2025年后全区按可开采量进行开采的开采方案最为合理,可分批逐次实现水源地的采补平衡。

The Daxing overlapping uplift area is located in the middle and lower reaches of the alluvial-proluvial plain of the Yongding and Chaobai rivers in the south of Beijing.The karst water under the quaternary aquifer has good quality and large storage.With the development of the urban area,the demand for groundwater has increased.Leadings to increased use of the karst water.With the continuous decline of the karst water level,it is essential to assess the groundwater resource and analyze the exploitation plan.A numerical model was set up by means of GMS,simulating the karst groundwater flow system and predicting variations in the groundwater level.The model was conceptualized with five layers,the 1st and2 nd layers are quaternary aquifers,the 3rd to 5th layers are karst aquifers.The model was calibrated using historical data spanning 12 years and 9 months.According to the model＇s water budget,the recharge of the groundwater system is 14,425.74×10^4m3/a,the total allowable exploitation of the groundwater system is14,310.52×10^4m3/a,of which the karst aquifer is 2,309.36×10^4m3/a.Analysis of the groundwater budget indicates,that the main recharge of the karst water aquifer is the leakage from the upper quaternary aquifer.Considering the local hydrogeological condition and the groundwater supply conditions,four exploitation plans have been proposed,（1）Maintain current exploitation;（2）Exploit according to the allowable exploitation level;（3）Maintain current exploitation until 2020,exploit by according to allowable exploitation level after 2020;（4）Maintain current exploitation until 2020,then stop the Niantan water source exploitation after2020,and exploit according to the allowable exploitation level after 2025.By analyzing the stage hydrograph of typical observed well and the water balance,The 4th plan is the best exploitation plan.In conclusion,the model is fit to describe the local hydrogeological features and has been successfully applied to predict changes in groundwater level.