The south west USA definitely has a problem of too many people and too little water.
Manitoba has plenty of water and almost yearly flooding. A pipeline south for money might be a good idea.
As for California, I'd suggest they look at a pipeline south from the Colombia river in Oregon. Plenty of fresh water headed to the sea. A pipeline along the coast where few people live all the way to LA.
Draining the great lakes is an idea that I would be cautious of, as its water shed is quite small. But Canada should be spending more time and money looking ahead in time.