Effect Of Tidal Fluctuations On Ground Water Levels In Coastal Areas

The study area lies in the northern coast of the Beibuwan, Beihai, Guangxi. The sea exists in the northwest, west and southwest, and the land in the north and east. The area in general is high in the north and low in south. The southern are is widened and relatively smooth. The study area is underlain by an unconfined aquifer and three confined aquifers. The groundwater in the confined aquifers receives recharge through leakage from the unconfined aquifer. Hydraulic connection exists between them, making a coastal loose the pore medium flowing multi-layer aquifer system. Precipitation, groundwater exploitation, surface water and so on will affect the change of groundwater level. Because the study area is a special area which is one of the three sides by the sea, So the influence of groundwater levels change one important factor also includes the periodical change of tides. This paper main task is to use Visual Modflow software simulation in coastal area by ocean influence the dynamic characteristics of groundwater aquifer,ocean and coastal regions of the fluctuation of groundwater cycle time,and each observation Wells a wave curve fitting and prediction.This paper mainly uses the observation data and Visual Modflow software for simulation, comprehensive analysis due to tidal influence of groundwater wave and tidal wave aquifer relationship in the coastal area. And there should be summarized in coastal area the groundwater variation amplitude with the distance of coast's change rules.This paper mainly use the each observation wells actual observation data of tidal to simulate, then compare with simulation value and observations, to determine Visual Modflow software simulation method of accuracy. Research area can be reference four times observation data as follows: the September, 1987(about 1 day), the November, 1987 (about 6 days), the January, 1993 (about 5 days), the December, the 1986 (about 37 days) ,the interval of observation is one hour.This paper use the VM software to simulate tidal cyclical change costal aquifer groundwater cyclical change and not performed at the same time, Costal aquifer underground water level fluctuation backward the tidal.The curves of water level fluctuation of the November, 1987, use the software of Visual Modflow to calculate every observation point's groundwater levels chart, in error allowed range, simulation with actual observation water figure drawing consistent. Therefore reoccupy 1986 37d and 1987 1d the observation data for verification, the results show that the model can better curve fitting of volatility, can use the model prediction of long-term underground water level and obtain satisfactory results.