What happens when a reservoir goes dry
The wild political madness involved in the grand project to water the American West is detailed in Marc Reisner's "Cadillac Desert" (1986), and is a must-read for anyone wanting to understand the current situation.  It was written before a climate-related megadrought was really on anyone's long-term radar, but it really explains a lot.For example, dams are only part of the water storage picture, there's also groundwater, and the water projects often had the goal of protecting groundwater (keeping the water table closer to the surface), but then once they'd provided water via a dam or aquaduct, the farmers would just expand the areas they were farming and groundwater extraction would often increase as a side effect.Humans really aren't that good at long-term planning, is one conclusion.