It is not essential to build a storage or impounding reservoir if the water can be stored in the ground. 如果能将水储存在地下，就没有必要建造水库或蓄水池。
To begin to understand why, remember that water in a reservoir naturally flows preferentially to any crack in the dam. 要探究原因，可以联想一下蓄水池的水，当水坝有裂缝时，水很自然的会先由裂缝流出。
