Any rainfall that excess the handling capacity of the downstream drainage network will be temporarily stored in this water tank.

雨量一旦超过地下排水系统的处理能力，则会被暂时储存在这个水罐中。

Like take a look at a drainage network for the Luangwa tributary of the Zambezi.

比如看看 赞比西河卢安瓜支流的排水网络。