Study On Groundwater Flow And Solute Transport In Coastal And Estuarine Region

This paper presents a systematic research on the groundwater environment in the coastal and estuarine region with the masterstroke of "tidal property". Te groundwater flow, especially the tidal groundwater dynamic in sandy beach and estuarine deltaic zone; and solute transport in the coastal and estuarine region, especially the tidal motion of fresh-salt water mixing zone in the subterranean estuary; and a new optimal method is induced in the simulation. As a result, some beneficial results are obtained.(1) Simulating the groundwater fluctuations effected by cutoff wall by use of analytic method, which is based on principle of similitude. The similarity parameters can be got through method of function analysis. Combined with the differences of groundwater levels with cutoff wall or not, analytic solutions are used for the evaluation of groundwater environmental effect.(2) Classical control theory is introduced in to the problem of groundwater fluctuations response to the tidal signals. Semi-infinite aquifer is defined as a single input-output system and the aquifer system is described by use of transfer function. It is the testify of principle of similitude.(3) A new two-dimensional model of groundwater fluctuations in estuarine zone is built. Using complex transform, the two-dimensional flow equation subject to periodic boundary condition (sea tides and estuarine tides) is changed into time-independent elliptic problem. Based on Green's function method, an analytical solution for groundwater fluctuations in fan-shaped aquifer is derived. We describe how groundwater's response to tidal loading in an estuary and ocean. Result shows its more extensive application than recent studies.(4) Based on the property of governing equations for problem of two-dimensional estuarine tidal groundwater fluctuations, this paper adopted method of coordinate transformation to derive the analytical solutions of tidal groundwater fluctuations in anisotropic media. These solutions are the extension of newly derived analytical solutions for tidal groundwater in fan-shaped anisotropic aquifer.(5) As a basic factor in the environment of coastal zone, tidal effects in the coastal aquifer have recently attracted much attention because tidal dynamic also greatly influences the solute transport in the coastal aquifer. As we know, tide-induced head fluctuations are a natural phenomenon in a coastal aquifer. Groundwater level change corresponding to the tidal waves. Tide is the power of salt-freshwater mixing. Based on density dependent numerical model, this paper focuses on tidal effect on the dynamic of salt-freshwater mixing zone. Results show that tide fluctuations induce the local circulation in the subterranean estuary.(6) Based on limited observed data, a pilot study is focused on groundwater motion in subterranean estuary with effects of surface estuary which become groundwork for future study.(7) Tabu search method, a meta-heuristic approach, with which simulated annealing and genetic method are extensively used in combinational optimization. Tabu search method is applied and validated its effectiveness to get the optimal parameter zonation in the simulation of groundwater movement in the north branch of Yangtze River Estuary This method, which is based on human memory, has shown the predominance of random search.