USGS Water-Year Summary 2017
11275500 Hetch Hetchy Reservoir at Hetch Hetchy, CA
LOCATION - Lat 37°56'52", long 119°47'13" referenced to North American Datum of 1927, in NW 1/4 NW 1/4 sec.16, T.1 N., R.20 E., Tuolumne County, CA, Hydrologic Unit 18040009, Yosemite National Park, near center of O'Shaughnessy Dam on Tuolumne River at Hetch Hetchy, 1.5 mi downstream from Falls Creek, and 5.9 mi (air line) northeast of the town of Mather.
DRAINAGE AREA - 455 mi².
PERIOD OF RECORD - May 1923 to current year. Prior to October 1930 monthend contents published in WSP 1315-A.
REVISED RECORDS - WSP 1930: Drainage area.
GAGE - Water-stage recorder installed March 1995. Datum of gage is 1.84 ft above NGVD of 1929. Prior to Oct. 1, 1927, nonrecording gage at same site and datum. Oct. 1, 1927, to July 9, 1972, water-stage recorder at same site and datum. Prior to October 1974, datum published as at mean sea level.
EXTREMES FOR PERIOD OF RECORD - (at 0800 hours) Maximum contents, 369,100 acre-ft, Dec. 3, 1950, gage height, 3,810.4 ft; no contents at times in 1929-31.