LOCATION--Lat 42° 38’03", long 71° 39’30", Middlesex County, Hydrologic Unit 01070004, on left bank 0.7 mi downstream from Trout Brook and 2.7 mi northwest of West Groton.
DRAINAGE AREA--63.7 mi², excludes 2.16 mi², above outlet of Ashby Reservoir.
PERIOD OF RECORD--Discharge: October 1949 to current year.
Water-quality records: Water year 1957.
REVISED RECORDS--WDR MA-RI-84-1: drainage area.
GAGE--Data Collection Platform with satellite telemeter. Datum of gage is 243.50 ft above NAVD 1988. Prior to May 13, 2020, datum of gage reported as 244.27 ft above NGVD 1929.
REMARKS--Occasional regulation at low flow by mill upstream; regulation greater prior to 1961. Entire flow from 2.16 mi² upstream from outlet of Ashby Reservoir diverted for municipal supply of Fitchburg except for occasional periods of spill.
COOPERATION BY-- Massachusetts Department Of Conservation and Recreation, Office of Water Resources.