I always thought watersheds were a great way of defining state-level regions. They're more stable than boundaries set by rivers, and are more natural than arbitrary lines of latitude/longitude. In the (near) future, there's going to be a lot of hand wringing over who has what rights to which water. The only way to completely solve it is to have one region be in control of the entire course of the water's flow.<p><a href="https://www.washingtonpost.com/blogs/govbeat/wp/2013/11/19/map-the-united-states-of-watersheds/?noredirect=on&utm_term=.0f5a35bcd78c" rel="nofollow">https://www.washingtonpost.com/blogs/govbeat/wp/2013/11/19/m...</a><p>Granted, redrawing the map based on watershed doesn't solve India's problem. But, it sounds like that in the future their drinking water is going to come from careful management of groundwater, which will require a lot of state level agreements. Right now, I'm not optimistic those agreements will happen smoothly.