Rivers can differ in size and there is no strict rule on how big a flow of water must be to be called as a river.
河流的流域会有不同，对于有多大的流量才能被称为河流没有严格的规定。
Recently, there has been progress towards durable water treaties for several big African river systems, such as the waters that flow down off the Lesotho highlands.
最近，一些有关非洲大型河流系统（比如流向莱索托高地的河流）的稳固的水协议正取得积极的进展。
Water flow into homes is a big challenge, even in Accra.
让水流入家庭是个严峻的挑战，即使是在阿克拉。
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