LOCATION--Lat 42° 38’45", long 71° 17’56", Middlesex County, Hydrologic Unit 01070002, on right bank at Lowell, 1,100 ft downstream from Concord River.
DRAINAGE AREA--Total above gage, 4,635 mi²; net above gage, 4,421 mi^2—excludes 214 mi² for use of Boston metropolitan district and city of Worcester.
PERIOD OF RECORD--Discharge: June 1923 to current year.
Water-quality records: Water years 1954, 1966–74, 1999.
GAGE--Data Collection Platform with satellite telemeter. Datum of gage is 5.18 ft above National Geodetic Vertical Datum of 1929. Prior to Mar. 7, 1934, at Boot Mills, 1,800 ft upstream and 700 ft above mouth of Concord River, in same gage pool 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.
REMARKS--Daily discharge includes water released from 210 mi² in basins of Sudbury and Nashua Rivers and Lake Cochituate. Flow regulated by powerplants, by Franklin Falls Reservoir since 1942, and by Squam, Newfound, Winnipesaukee, Winnisquam, and other lakes and reservoirs upstream.
COOPERATION BY--Massachusetts Department of Conservation and Recreation, Office of Water Resources.