Parts of three states- California, Nevada, Arizona- and a chunk of Mexico depend on the Colorado River for water, and that supply is rapidly running out. As climate change cuts into the snowpack in the Rocky Mountains and affects the timing of the snowmelt, less water is available to recharge the lakes and reservoirs along the way. Fortunately, being a country with a well-established system of laws, we have peaceful means of handling it: I have some friends who are "watermasters" in Nevada, and there are all sorts of conferences and arbitration over who gets what. It's not always an efficient system, but at least it's not like in some countries.
In other places, people anticipate that this century might well see wars over water, particularly in climatically stressed areas such as central Asia. Resources are stressed all over, and this "slow motion crisis" looks to get worse before it gets better. Some of the good news is that in dry countries like Kazakhstan, it's already clear that water is going to be an issue, and so they've begun to take action.
When something gets scarce, people start to see it as valuable, and they are more careful with it. Supply and demand start to matter. Economics at work!