I live in Oregon and AFAIK the idea of shipping (diverting?) water from the Columbia to California has been a recurring theme that is, so to speak, "dead in the water" before the ink dries on the planning documents. (Yeah I know, paperless, etc., but the really big plans seem to never escape printouts.)

FWIW in Portland water isn't at all a cheap resource which speaks to the costs of even fairly local transport and delivery. (Portland's water source is ~60 miles east at Mt. Hood.) To me it suggests attempting to share water with very distant areas would be an extremely expensive/complex engineering feat that would dwarf construction of the new Panama canal. Even a project of such scale is by comparison merely a backyard ditch.