water flowing through the o`shaughnessy dam spillway due to high water levels in the hetch hetchy reservoir, yosemite national

alpine america architecture attraction barrage california concrete construction control dam drain drainage due embankment engineering flood floodgate flow flowing gate hetch hetchy high industry lake level levels management mountains national nature nevada oshaughnessy outdoor outdoors overflow park reservoir runoff sierra sluice spill spillway states stream structure technology tourism tourist united usa view water yosemite