液态的水总是最快的路线降低高度。雨水会流垂直到地下水表面如果不是渗透率(有限)[1]的[材料属性][2]。渗透率控制水的速度(渗透)[3]和穿透材料。例如,地表径流水量的硬路涂料,当水从一个喷壶进入花坛的软土。砾石、砂和破碎岩石渗透率高的页岩和non-fractured火成岩低渗透。如此之低,这在许多情况下,似乎是完全令人费解的人类时间尺度。这同样适用于一条河。如果河流透水岩石,典型的沉积物沉积在河边本身*(见图)*,地下水也会流入河床下的沉积物,允许水仍然是进入上游。一种更好的方式来了解河流或湖泊在这种背景下,是它的表面表现(地下水位)[4]。如果你挖一个好身体旁边的水你会达到地下水与河水表面相同的高度。 The gradient of the groundwater surface and the permeability of the material controls the direction and velocity of the flow. However, if more water enters a system than the surface can infiltrate, the surplus will flow as surface runoff, typical for wadis *(See picture)* in desert areas. ![Wadi. Photograph taken by Mark A. Wilson, The College of Wooster][5] So, to answer your question. It depends on the local geology, but ground water will always flow from the [precipitation][6] area to the oceans (or a lower point where it can evaporate or being pumped up). Ground water exists everywhere and the gradient of the hydrostatic pressure controls the direction of the flow. As viable rivers shows the ground water table, it is usually rather safe to assume that the ground water under the dry river flows more or less the same direction. However, ground water flow can be changed by e.g. pumping from irrigation wells. Imagine a flat lying river bed with a well upstream. When enough water is removed from the well and eventually evaporated, ground water will flow towards the well. The water don't 'remember', but follows the law of gravity. [1]: https://en.wikipedia.org/wiki/Darcy%27s_law [2]: http://all-geo.org/highlyallochthonous/2011/01/geology-is-destiny-globally-mapping-permeability-by-rock-type/ [3]: https://en.wikipedia.org/wiki/Surface_runoff [4]: https://en.wikipedia.org/wiki/Water_table [5]: http://i.stack.imgur.com/JWOl5.jpg [6]: https://en.wikipedia.org/wiki/Precipitation