Gold Rush Alaska

In Northern California most of the rain and snow come from mid November to April.
Above say 4000 feet it is usually snow. Up at the summits of the Sierra they can get more than 30 feet of snow in a winter.
That is all usually melting in June. You get alot of run of from about April thru June here.
I guess they feel without dams the valley would be a big swamp around then every year.