And when we did that, we had to build storm sewers to get the water that fell on the cities out before it could cause flooding, and that's a waste of a vital water resource.
这样一来，我们必须修建巨大的排水管道， 将落在城市里的雨水排出去， 以免引发洪灾， 这对水资源是极大的浪费。