Drops in the bucket
I just installed a rain barrel at my home, provided by the city of Los Angeles' rainwater harvesting program (which is not accepting new applicants, but does have a waiting list).
This isn't the most viable solution for making us in LA more water-secure. It only collects 60 gallons of rainwater, a thimble full. But it is a solid step in the right direction.
Instead of 60 gallons, we should be collecting thousands of gallons per household so we can replace a substantial amount of the water that must be imported to water our landscapes.
Does this surprise you? Every time it rains one inch in Los Angeles we throw away 7.6 billions of gallons of rainwater. Imagine if there was a cistern, with the capacity of thousands of gallons, at each home or parcel of land.