Map Of The Columbia River Dam System

The above map shows the Columbia river dam system. As you will notice it includes Canada, Idaho, Oregon, Washington and small parts Nevada and Western Montana. 

California isn't connected to the system and there is no giant

 

So let’s consider the nonexistent valve, which he discussed during his campaign, and the needlessly empty half-pipe, a newer imponderable that he brought up at the Friday LA roundtable before issuing his order. In Trump’s view, this imagined infrastructure lets “hundreds of millions of gallons of water flow down into Southern California” from the north, if only we’d let it.

How far north? Trump earlier spoke of Northern California, but by Friday he said the source was “the Pacific Northwest.” By the end of the day he claimed the water flowed down — “naturally” — from Canada.