地下水动力系统对填海造陆的时空响应机理

Land reclamation is an effective measure to alleviate increasingly severe problems of land scarcity and to expand the space for survival and development. The implementation of land reclamation can disturb the original balance of water exchange between freshwater and seawater, and result in the redistribution and re-equilibrium processes of freshwater and saltwater resources, which influence the two most important processes in coastal aquifers: seawater intrusion and submarine groundwater discharge. The temporal and spatial response of groundwater hydrodynamic systems to land reclamation could be affected collectively by a number of factors, including coastal hydrogeological conditions, boundary hydrodynamic conditions, shoreline morphology, materials used in reclamation, and reclamation speed. With the research background of extensive land reclamation activities in our country, the project aims to investigate comprehensively and systematically the impact of land reclamation on groundwater hydrodynamic systems, using the methods of field investigation, on-site monitoring, laboratory experiments, and numerical modelling. In specific, the coupled effects of various hydrogeological factors and land reclamation on groundwater level, saltwater wedge, freshwater-seawater mixing, and groundwater outflow will be explored, and the quantitative model between land reclamation and the response of groundwater hydrodynamic systems will be constructed. The results expected could provide an important scientific basis and theoretical support for the feasibility assessment of land reclamation, and the protection of coastal aquifers and offshore environments.

填海造陆是海岸带解决日益严峻的土地赤字，扩大生存和发展空间的有效途径。填海工程会打破海岸带地下水系统中原始的海陆水交换平衡，使咸淡水资源进行再分配、再平衡过程，从而影响海岸带含水层两个最重要过程：海水入侵和海底地下水排泄。海岸带地下水动力系统对填海造陆的时空响应受多因素的协同影响，包括：海岸带水文地质条件、海陆边界水动力条件、海岸线形态、填海材料的渗透性与造陆速度。本项目以全国大规模填海造陆活动为研究背景，拟采用野外调查、现场观测、室内试验、数值模拟等手段，全面、系统、深入研究填海造陆对地下水动力系统的影响，探索各种水文地质因子与填海活动耦合作用下地下水位、盐水楔位置、咸淡水混合及地下水出流的时空变化规律，建立填海造陆工程与地下水动力系统响应之间的定量模型。研究成果将为填海造陆工程前期的可行性评估、滨海含水层和近海水环境的保护提供重要的科学依据和理论支撑。

随着全球人口数量的增加，土地资源越发匮乏，人们开始转向海洋寻找更多的生存与发展空间。填海造陆工程由此应运而生，并逐渐发展，但该工程势必会打破海岸带地下水系统中原始的海陆水交换平衡，其对海岸带海水入侵的影响有待研究。海岸带地下水动力系统对填海造陆的时空响应受多因素的协同影响，本课题综合考虑了海岸带水文地质条件、海陆边界水动力条件、填海材料的渗透性等影响，部分主要结果如下：1）给出了海岸带分层含水层咸淡水交界面的解析解，可减少实际问题中海水入侵位置估计的不确定性；2）给出了海水入侵与回退的时间不对称性的解析解，揭示了其时间不对称性主要依赖于内陆边界淡水流量的初值与终值；3）给出了海平面上升对分层含水层海水入侵的解析解，揭示了承压与非承压含水层，定流量与定水头边界条件对海平面上升的不同的响应机制；4）将填海造陆由海岸带推广至人工海岛，从而提出了通过在靠海侧构建低渗透介质层的方法来增加海岛淡水储量，结果表明该方法可极大地增加海岛淡水储量。研究结果可为填海造陆工程前期的可行性评估、滨海含水层和近海水环境的保护提供重要的科学依据和理论支撑。