USGS Water-Year Summary 2021
01100000 MERRIMACK RIVER BELOW CONCORD RIVER AT LOWELL, MA
LOCATION - Lat 42°38'45", long 71°17'56" referenced to North American Datum of 1927, Middlesex County, MA, Hydrologic Unit 01070002, on right bank, 400 ft downstream from Rt 38, and 1,100 ft downstream from Concord River.
DRAINAGE AREA - 4,635 mi² of which 214 mi² probably is noncontributing.
PERIOD OF RECORD - Discharge: June 1923 to current year. Water-quality records: water years 1954, 1966-74, 1999-2004.
GAGE - Data Collection Platform with satellite telemeter. Datum of gage is 4.37 ft above NAVD 1988, from U.S. Army Corps of Engineers benchmark. Datum previously reported as 5.18 ft above NGVD 1929, from U.S. Army Corps of Engineers benchmark. Prior to Mar. 7, 1934, at Boott Mills, 1,800 ft upstream which is 700 ft upstream from the mouth of the Concord River, but is in the same gage pool as present and at same datum; gage-height record (provided by Proprietors of the Locks and Canals on Merrimack River) was indicative of flow including that of Concord River.
COOPERATION - Massachusetts Department of Conservation and Recreation, Office of Water Resources.
PERIOD OF RECORD - Water-quality records: Water years 1954, 1966-74, 1999 to 2004.