Certainly we could curb our water use. Do we even have enough sites to build dams which would solve the problem? Otherwise we should consider the relative merits of golf courses and agricultural production and allocate accordingly.

Golf courses use a minuscule fraction of California's total water supply. Many of them are now irrigated by gray water.

The major fresh water use is mostly agriculture. We need to eat, but on the other hand a lot of that water ends up getting used to grow alfalfa for export to Saudi Arabia: profitable for certain farmers, not great for the rest of us.

https://www.pbs.org/newshour/politics/in-drought-stricken-ar...

If you're operating under the idea that we can't expand the supply of water, then you basically believe California is full. It would then follow that you would be against immigration, since more people would only exacerbate the problem.