We need to build more resilient infrastructure, and in this case desalination plants. In the past desalination plants have been environmentally unfriendly but new technology is now available to build very sustainable desalination plants. There is no reason coastal cities should run out of water.
San Francisco used to have Dutch windmills that pumped in water to Golden Gate Park in the 1800s and irrigated it. There is no reason we can’t do something similar to coastal cities. Now San Francisco is using reclaimed water to irrigate GGP. This is also a more sustainable practice.
So water is a solvable problem with the right infrastructure. Unfortunately building resilient infrastructure isn’t as sexy as talking about climate change, so we just don’t address it enough.