GroMoPo Metadata for Shenzen FEFLOW model

During the 1990s, groundwater overexploitation has resulted in seawater intrusion in the coastal aquifer of the Shenzhen city, China. Although water supply facilities have been improved and alleviated seawater intrusion in recent years, groundwater overexploitation is still of great concern in some local areas. In this work we present a three-dimensional density-dependent numerical model developed with the FEFLOW code, which is aimed at simulating the extent of seawater intrusion while including tidal effects and different groundwater pumping scenarios. Model calibration, using waterheads and reported chloride concentration, has been performed based on the data from 14 boreholes, which were monitored from May 2008 to December 2009. A fairly good fitness between the observed and computed values was obtained by a manual trial-and-error method. Model prediction has been carried out forward 3 years with the calibrated model taking into account high, medium and low tide levels and different groundwater exploitation schemes. The model results show that tide-induced seawater intrusion significantly affects the groundwater levels and concentrations near the estuarine of the Dasha river, which implies that an important hydraulic connection exists between this river and groundwater, even considering that some anti-seepage measures were taken in the river bed. Two pumping scenarios were considered in the calibrated model in order to predict the future changes in the water levels and chloride concentration. The numerical results reveal a decreased tendency of seawater intrusion if groundwater exploitation does not reach an upper bound of about 1.32 x 10(4) m(3)/d. The model results provide also insights for controlling seawater intrusion in such coastal aquifer systems.

在20世纪90年代，深圳市沿海含水层因地下水过度开采而出现海水入侵现象。尽管近年来供水设施得到改善，海水入侵问题有所缓解，但在部分地区地下水过度开采依然令人担忧。本研究采用FEFLOW代码构建了一个三维密度依赖性数值模型，旨在模拟海水入侵范围，并考虑潮汐效应及不同的地下水抽采情景。模型校准基于14个井孔的数据，这些井孔自2008年5月至2009年12月进行了监测，并利用水位和报道的氯离子浓度进行。通过手工试错法，实现了观测值与计算值之间相当良好的拟合。采用校准模型对模型进行了为期3年的预测，考虑了高、中、低潮位及不同的地下水抽采方案。模型结果表明，潮汐引起的海水入侵显著影响了大沙河河口附近的地下水位和浓度，这表明即使考虑到河床采取了一些防渗措施，该河与地下水之间仍存在重要的水力联系。校准模型考虑了两种抽采情景，以预测未来水位和氯离子浓度的变化。数值结果表明，如果地下水抽采不超过约1.32 x 10(4) m(3)/d的上限，海水入侵趋势将有所降低。模型结果为控制此类沿海含水层系统中的海水入侵提供了有益的见解。