The other side of the mountains? North West? We do take water from the Western side of the Sierras. What mountains are you talking about?
As for local, we bring water in now from over 400 miles away.
Northwest, reservoir it there, pump it over the mountains during the drier times of the year into the rivers in Northern California, then pump it into the canals. Then pump it one more time into the reservoirs in the southern valley.