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- Water-Year Summary reports summarize a year of hydrologic data in a printer-friendly format.
- For water years 2014 onward, choose a water year and parameter and an on-demand Water-Year Summary report will be generated.
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USGS Water-Year Summary 2024
01094000 SOUHEGAN RIVER AT MERRIMACK, NH
LOCATION - Lat 42°51'27", long 71°30'24" referenced to North American Datum of 1927, Hillsborough County, NH, Hydrologic Unit 01070002, on left bank, at head of Wildcat Falls, 0.6 mi upstream from south bound bridge on Everett Turnpike, 0.9 mi southwest of Merrimack Town Hall, 1.3 mi upstream from mouth, 1.7 mi northwest of Litchfield Town Hall.
DRAINAGE AREA - 171 mi².
REVISIONS HISTORY - WSP 431: 1909-14. WSP 726: Drainage area. WSP 781: 1924(M). WSP 1231: 1914-15(M), 1917(M), 1919-23(M),
1927-28(M), 1929, 1930-34(M).
SURFACE-WATER RECORDS
PERIOD OF RECORD - Discharge records: July 1909 to September 1976, October 2001 to current year. Partial-record station: October 1976 to September 2001. Peak streamflow: Water years 1910 to 1976, 1980, 1982 to current. Water-quality discrete samples: Water years 1953, 1967 to 1976, 1979 to 1984, 1986, 1987, 1989 to 1999. Miscellaneous discharge measurements: Water years 1979 to 1984, 1986 to 1987, 1989 to 2001.
GAGE - Water-stage recorder. Datum of gage is 159.88 ft above North American Vertical Datum of 1988. Prior to April 12, 1911, nonrecording gage at site 300 ft downstream at datum 0.38 ft lower. April 12, 1911 to October 14, 1913, nonrecording gage at present site and datum.
COOPERATION - National Streamflow Information Program and the U.S. Army Corps of Engineers, New England District.
REMARKS - Water Years 2014-19: Records good except those for estimated discharges, which are poor. Water Years 2020-22: Records fair except those for estimated discharges, which are poor. Slight diurnal fluctuation at times caused by mill upstream. Diversion to Pennichuck Brook basin for municipal supply of Nashua during periods of low flow from August 1965 to October 1966, July 1969 to November 1971, October 1972, October 1973, July to September 1974, June to August 1975, June to September 1976. High flow slightly affected by retarding reservoirs since 1963.
EXTREMES FOR PERIOD OF RECORD - Maximum discharge, 16,900 ft³/s, March 19, 1936, gage height, 16.2 ft, from rating curve extended above 7,300 ft³/s on basis of velocity-area studies and computation of flow over dam at gage height 12.78 ft; minimum discharge, 3.8 ft³/s, August 17, September 8, and October 1, 1965. Stage and discharge from the flood of March 19, 1936, are the greatest since 1830.
