滨海河网地区海水入侵引起的变密度地下水演化过程模拟研究

Seawater intrusion is one of the most common groundwater contaminations in coastal aquifers. A density-dependent groundwater numerical model is constructed to simulate chloride transport behavior and movement law of freshwater-seawater transition zone, to reconstruct the seawater intrusion process, and to predict the future extent of seawater intrusion in coastal aquifers. In seawater intrusion area based on river network system, the surface water and groundwater interact frequently which are needed to be treated as a whole. Combining with the previous research and the latest information, a distributed numerical simulation code of seawater intrusion, namely Xinanjiang-SEAWAT, is developed by coupling the improved Xinanjiang model with a density-dependent groundwater flow and solute transport simulator, SEAWAT, through the groundwater recharge. A simulation model is developed in Huangshui river basin of Laizhou bay in Shandong Province by running Xinanjiang-SEAWAT model, simulating accurately the changing position of freshwater-seawater transition zone in seawater intrusion area under the impact of the surface water system based on river network system, studying the density-dependent groundwater evolution process in seawater intrusion area based on river network system, providing the theoretical basis for predicting the future extent of seawater intrusion and controlling the future deterioration of groundwater quality in seawater intrusion process.

海水入侵是滨海含水层地下水水质恶化最普遍的方式之一。在滨海含水层海水入侵区建立变密度地下水模拟模型，可模拟氯离子运移行为及抽水条件下咸、淡水过渡带的移动规律，再现海水入侵过程并预测未来海水入侵趋势。滨海河网地区地表水和地下水转化关系较为密切，需要从过程上把两者作为一个整体系统进行研究。结合前人研究成果及最新资料，通过地下水补给量将改进的新安江模型与变密度地下水模拟程序SEAWAT相耦合，构建新安江-SEAWAT分布式海水入侵数值模拟模型，将其应用于山东省莱州湾黄水河流域滨海地区，较为精确地模拟河网发育的地表水系统影响下海水入侵区咸、淡水过渡带的移动，研究滨海河网地区海水入侵引起的变密度地下水演化过程，为预测海水入侵趋势并控制海水入侵程度进一步加重提供了理论依据。

海水入侵是滨海含水层地下水水质恶化最普遍的方式之一。在滨海河网地区，由于地表河网系统对变密度地下水系统的补给量在模拟中较难准确估量，故其对模拟精度及未来海水入侵程度预测精度影响较大。目前为止有关适用于滨海河网地区变密度条件下地下水模拟模型的研究尚较薄弱。本研究将尝试构建适用于滨海河网地区的地表水-地下水模拟模型，通过地表水文模型和变密度地下水模拟模型的松散耦合，选定山东省莱州湾黄水河流域滨海地区为代表性研究区，开展地表河网系统对变密度地下水演化过程影响的模拟研究，并基于收集数据进行了模型的校正和验证。研究结果表明，水流模型经校正后相关系数为0.9749，溶质运移模型经校正后相关系数达为0.8957，拟合效果良好，模型基本满足精度。研究成果将可为滨海河网地区地下水资源开采管理提供技术支持。