USGS Water-Year Summary 2020
01100693 MERRIMACK RIVER, 0.3 MILES UPSTREAM FROM RT 125 AT HAVERHILL, MA
LOCATION - Lat 42°46'22", long 71°04'59" referenced to North American Datum of 1983, Essex County, MA, Hydrologic Unit 01090002, on left bank, in a U.S. Army Corps of Engineers diversion/pump house built in 1939, about 0.4 mi upstream from Rt 125 bridge in Haverhill. The facility is owned and maintained by the City of Haverhill Sewer Department.
DRAINAGE AREA - 4,850 mi² of which 214 mi² probably is noncontributing.
PERIOD OF RECORD - June 2006 to current year.
GAGE - Data Collection Platform with satellite telemeter. Datum of gage is 0.80 ft below NAVD 1988. Prior to May 8, 2020, datum reported as NGVD 1929.
COOPERATION - Massachusetts Department of Conservation and Recreation, Office of Water Resources.
EXTREMES FOR PERIOD OF RECORD - Maximum gage height, 17.64 ft, April 18, 2007; minimum measureable gage height, -0.33 ft, many days during water years 2006 to 2011. Gage height is not measureable below -0.33 ft when intake is out of water.