USGS Water-Year Summary 2024

11264500 Merced River at Happy Isles Bridge, near Yosemite, CA

LOCATION - Lat 37°43'53", long 119°33'29" referenced to North American Datum of 1927, Mariposa County, CA, Hydrologic Unit 18040008, unsurveyed, in Yosemite National Park, on left bank, 30 ft upstream from remnants of footbridge at Happy Isles, 0.4 mi downstream from Illilouette Creek, and 2.0 mi southeast of Yosemite National Park Headquarters.

DRAINAGE AREA - 181 mi².

REVISIONS HISTORY - WSP 1215: 1938 (instantaneous maximum discharge).

SURFACE-WATER RECORDS

PERIOD OF RECORD - August 1915 to current year.

GAGE - Water-stage recorder. Datum of gage is 4,020.46 ft above NAVD of 1988.

REMARKS - Up to 5 ft³/s can be diverted upstream from station.

EXTREMES FOR PERIOD OF RECORD - Maximum discharge, 10,100 ft³/s, Jan. 2, 1997, gage height, 13.27 ft, from rating curve extended above 4,000 ft³/s, on basis of contracted-opening measurements at gage heights 10.4 and 11.55 ft; minimum daily, 1.5 ft³/s, Sept. 26, 1977.

WATER-QUALITY RECORDS

PERIOD OF RECORD -

DISCRETE WATER-QUALITY DATA:
CHEMICAL DATA: Water years 1968-96, 2001-03.
BIOLOGICAL DATA: Water years 1973-81.
SEDIMENT DATA: Water years 1970-71, 1973-96, 2001-03.

CONTINUOUS WATER-QUALITY DATA:
WATER TEMPERATURE: Water years October 1965 to September 1977, October 1978 to September 1993, March 2012 to current year. (water years 1966-1977, 1979-1993, 2012-2023, daily). 

INSTRUMENTATION - Temperature recorder water years 1966-77, 1979-93, and since March 2012.

REMARKS - The practice of rating water quality records was discontinued in the 2017 water year.