This is an excellent idea but the environmentalists will block it. Why waste all of that flood water when we could divert it to where it is needed? Desalination is hideously expensive.
When I lived in Texas I used to notice a 2 degree drop when crossing the man-made lakes near Tyler,Texas and the temperature would go up as soon as I crossed onto dry land.
In 2011 it was 118 degrees in Plano, Texas and 160 degrees on the pavement.
Save the water, put it where it can be used.
Governor Connolly proposed such an idea in 1964 and was shot down but it is doable. Don’t let anyone tell you otherwise. They are obstructionists until they are fighting over the last glass of water and then the scales will fall from their eyes. We can live without a lot of things but we can’t live without water.
When the flood is over, and the diversion pipe is dry, California will demand water anyway.
You will have to fill up that pipe at your own hurt.
Talk to a Delta Smelt for confirmation.