To make at least a dent in Houston's problems, it would have to be able to move 10 trillion gallons in a few days. But, hey, let's give it all year, just to make it easier. That's 27 billion gallons a day, just over a billion gallons an hour, 19 million gallons a minute, or 317,000 gallons a second. That's... improbable. That's 508,000 cubic feet per second.

Assuming a velocity of 1000 miles per hour, or 1467 feet per second (also improbable), you'd need a cross section of 346 square feet. That's a pipe that is 21 feet in diameter, which is not completely impossible. Or four pipes that are each 10.5 feet in diameter. That's doable. The 1000 miles per hour pumping speed is a bit of an obstacle, though...

You jest, but there are serious (abstract) proposals[2][1] to build inter-regional water banking mechanisms, such as pumping water from flood years in the Missouri/Mississippi watershed to be stored in CA/NV aquifers, and vice versa. It's not a bad idea.

[1] http://www.hcn.org/issues/47.4/the-water-czar-who-reshaped-c...

[2] https://www.reviewjournal.com/news/exit-interview-mulroy-tal...

California has only 20 million acre feet of reservoir capacity, which is currently filled to 125% of typical levels. The last thing that state needs is another 75 million acre feet of water.

Yeah, and the pumps/tunnels to get it over/under the Rockies and the Sierras.

US already has a wall to build.