Which are hydrographic basins where all the rainfall collects and drains off into a common outlet like a river or a bay by basing the political boundaries more on these natural watersheds.

这些都是水文盆地，所有的降雨都聚集在一起，然后排入一个共同的出口，比如河流或海湾，将政治边界更多地建立在这些自然流域上。