北京市平原区地下水开采量反演的数值模拟方法

Numerical simulations for groundwater withdrawal inversion in Beijing plain

准确获取地下水开采量统计数据是进行水资源管理的基础,但是由于诸多人为因素,北京平原区调查统计得到的开采量数据与实际产生的开采量有出入.本文提出了地下水开采量反演的地下水数值模拟方法.为获取更接近实际的地下水开采量,基于有限元数值模拟软件FEFLOW,建立了北京市平原区(不包括延庆盆地)地下水流数值模型,依据各行政区开采量对平均水位的灵敏度系数,利用2012—2014年111孔地下水监测井的月动态数据,通过拟合模拟水位和实测水位,采用人工试错法对各区的开采量数据进行反演校正.反演后得到北京市平原区2012—2014年总开采量分别为23.16亿、21.77亿和23.44亿m3.反演后各单孔模拟和实测地下水位拟合较好,模型能较为真实地反映北京平原区地下水动态.以顺义区为典型,利用模型分析了区域地下水位与地下水开采量的关系.模拟结果可为北京市分区县地下水管理考核工作提供决策支持.

Accurate measurements of groundwater withdrawal are essential for water resource management. Measurement errors are unavoidable in Beijing plain areas due to human factors. A method was proposed in the present study to inverse groundwater withdrawal by groundwater flow numerical simulations. A groundwater numerical model for Beijing plain areas （minus Yanqing plain） was developed with the popular finite-element software FEFLOW. Sensitivity of groundwater withdrawal to average groundwater level in each administrative county was used to adjust groundwater withdrawal. Groundwater withdrawal was inversed through artificial trials and errors by matching simulated and measured groundwater levels, which were obtained from 111 observation wells. With this method, estimated annual groundwater withdrawal in Beijing Plain was found to be 23.16× 10^8 m3 , 21.77×10^8 ma and 23.44×10^8 m3 respectively in 2012, 2013 and 2014. Simulated groundwater level fitted well with measured values in each county after inversion and the numerical model could be used to simulate groundwater dynamics in Beijing plain. The relationship between regional groundwater level and groundwater withdrawal was analyzed for Shunyi County. These results will provide decision support for county-based groundwater management in Beijing plain.