http://www.notechmagazine.com/2015/06/water-johads-a-low-tec...

LA has a drainage system that tries to get water out to the sea as fast as possible.

If the water is not hanging around, its not going to evaporate. So no clouds to be blown inland. Evaporating water takes energy, which lowers ambient temperature, etc.

Johads are dirt cheap, simple and effective. The basic premise is you put in half moon banks every n 100 meters. The idea is that it keeps back a certain amount of water. Excess water overflows into the same channels as before, so there is no risk of flooding.

Failing that, solar stills are much cheaper than reverse-osmosis to build, and in south California with loads of sun cheap and effective.

However you still have to transport the water.