USGS Water-Year Summary 2021
01130000 UPPER AMMONOOSUC RIVER NEAR GROVETON, NH
LOCATION - Lat 44°37'30", long 71°28'10" referenced to North American Datum of 1927, Coos County, NH, Hydrologic Unit 01080101, on left bank, 75 ft upstream from Emerson Road bridge, 0.2 mi downstream from Nash Stream, 2.8 mi northeast of Groveton, and 3.4 mi Northwest of Stark.
DRAINAGE AREA - 232 mi².
PERIOD OF RECORD - Discharge records: August 1940 to November 1980. October 1982-September 2004. July 2009 to current year.
GAGE - Water-stage recorder. Datum of gage is 916.43 ft above North American Vertical Datum of 1988 (levels by New Hampshire Department of Transportation).
COOPERATION - New Hampshire Department of Environmental Services and USGS Groundwater and Streamflow Information Program.
EXTREMES FOR PERIOD OF RECORD - Maximum discharge, 24,100 ft³/s, May 20, 1969, gage height 12.01 ft (from floodmarks), from rating curve extended above 8,700 ft³/s on basis of contracted-opening measurement of peak flow. Caused by failure of dam on Nash Stream. Minimum discharge, 26 ft³/s, September 11, 2002.