潮汐引起滨海承压含水层地下水位变化的数值模拟

摘要

Tidal fluctuations can cause coastal groundwater level fluctuations. Based on the finite difference method, we establish a numerical model in the coastal area of one - dimensional confined aquifer of groundwater. Described the tidal wave as sine wave, we obtained the tidal fluctuation change of underground water level. The results show that, under the tidal influence, the coastal aquifer underground water level and tide have similar volatility but amplitude decreases, along with the increase of the distance from the coast, groundwater level fluctuation and tidal efficiency was negative exponential declined, underground water level on the lag time linearly increased. For example, when confined aquifer water conduction coefficient is 31.25 m^2/h, water storage coefficient is 4.5 × 10^-4 and the amplitude of 2. 5 m, cycle of 24. 7 h, at a distance from the coast at 500 m, amplitude is 1. 352 68 m, tidal efficiency is 0. 541 07, the lag time of 1. 825 h. From the shore of up to 4 389 m, we can think groundwater levels affected by tidal fluctuations.%海潮波动可以引起海岸带地下水位发生波动。建立基于有限差分法的滨海地区一维承压含水层地下水运动数值模型。通过将潮汐波动概化为正弦波，模拟滨海地区地下水位随潮汐波动的变化。结果表明，受海潮影响的滨海含水层地下水位与海潮有相似的波动特征，但变幅减小，受海潮的影响程度与离海岸的距离有关，随着离海岸距离的增加地下水位的变幅及潮汐效率呈负指函数衰减，地下水位对海潮的滞后时间随距离呈线性增加。例如，当承压含水层导水系数为31．25m^2／h、储水系数为4．5×10^-4及海潮振幅为2．5m、周期为24．7h时，在距离海岸500m处，振幅为1．35268m,潮汐效率为0．54107，滞后时间为1．825h。在距海岸达4389m以远时可以认为地下水位不受海潮波动的影响。