河床地形影响潜流交换作用的数值分析

选取对潜流交换具有重要影响的河床地形作为主要研究内容,采用数值模拟(MODFLOW程序)的方法研究在河床横剖面地形不均匀的条件下,潜流交换量的空间分布以及地下水流场的演变机制。结果表明:在河床地形起伏不均的情况下,潜流交换量更易发生在河道的深水区域;地下水流向受河床地形影响较小;近河床界面处的地下水流速受地形起伏影响剧烈,深水区域的地下水流速远大于浅水区地下水流速;通过与现场试验结果对比分析,得出河床地形起伏是引起潜流带渗透系数非均质现象的重要原因之一。

Numerical analysis of the impacts of bedform on hyporheic exchange

The impacts of irregular bedform in cross section on hyporheic exchange are studied by means of numerical simulation computations. The computation of the hyporheic exchange rate is done using the modular finite-difference ground-water flow model (MODFLOW) developed by the United States Geological Survey. Results show that more hyporheic exchange occurs on the part of the streambed in deeper-water areas. The bedform has less influence on the groundwater flow direction. However, the groundwater flow close to the streambed exhibits a strong velocity gradient due to terrain effects. The groundwater flow velocity in the deeper-water area is far greater than that in the shallower-water area. In comparison with the hydraulic conductivity and the water depth obtained from the field experiment, the heterogeneity in hydraulic conductivity in hyporheic zone is likely due to the effect of irregular bedform in cross section.