Spoken like someone with absolutely no engineering experience. Engineering as a discipline has this impish habit delivering things most people never imagined possible. This misleads them into thinking that engineering can give them anything they can imagine, particularly if the concept seems simple to them.
Take the suggestion elsewhere in this discussion that water be piped from the Great Lakes to California. Nothing could be simpler in conception -- a 2000 mile long pipe. We've built oil pipelines longer than that. The longest crude oil pipeline in the world is the 2500 mile Druzhba pipeline from Russia to Germany, so a 2000 mile long water pipe should be a cinch, right?
Here we get to the place where engineering starts being a bitch. You see, it's one thing to imagine a cost-is-no-object project, but the truth is cost is the single most important limitation on water use. It does no good to supply water to California almond farmers if they have to sell their almonds at the same price/weight as gold to pay for it. We use a *lot* more water than oil, and we expect it to be way, way cheaper. The current spot price for crude oil is about $57 per barrel -- roughly $1.36/gallon. Agricultural users in California pay something like 3/10 of a penny a gallon -- roughly speaking they expect water to be about 500x cheaper per gallon than oil. If pumping adds a penny to the price per gallon to the price of crude oil, that's no big deal, less than 1%. Add a penny per gallon to the price of water and you've quadrupled your farmer's water cost.
A system that delivers water can be expensive to build, but it has to operate cheaply and reliably. That's why water systems engineers avoid pumps and rely on gravity to do most of the work of moving water. The longest water supply pipeline I know of is the Goldfields Water Supply Scheme, which transports water 330 miles with the aid of 20 pump stations. The economic justification for this project? To support gold mining. To give you an idea of how much expense was tolerated when the Goldfields system was built, it replaced a system where water was packed in by camel train. Today users there pay 7x as much per gallon as users in California do for water. Assuming the CA system could be operated for the same price, you could actually dispense with actually building the system. Raising the water price from $0.003 to $0.02 would reduce water consumption in California to sustainable rates -- even under drought conditions. It'd do so by causing agriculture to move out of state. Probably some population too.