Indeed. Worse, it's likely that "one of these years" will turn into "most of these years" before long.

It sounds like you know this already, but the core issue here is that the 1922 agreement which divided the river's flow to various stakeholders overestimated the amount of water in the river even before the impacts of our modern warmer, drier climate.

We're left with the consequences of this overestimate mostly in the form of gridlocked renegotiation conversations as the agreement is reworked for the modern resource scenario.

Probably the biggest tl;dr here is: it's not going to be 60 million people fighting over water. It's going to be far fewer, and they're all alfalfa farmers.