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ICE EFFECTS ON STREAMFLOW
The formation of ice on rivers can cause discharge values to appear unusually high. Display of these erroneous discharge data may result in improper assessment of flow conditions and misuse of the data. For this reason, display of discharge values for streams significantly affected by ice may be disabled from view. Display of discharge data will resume when ice conditions are no longer present. Discharge values for streams minimally affected by ice will continue to be displayed. Flows for streams with these conditions appear to increase during the night and decrease to near-base-line conditions around midday. To estimate the correct discharge for these streams, use the flow rate that corresponds to the bottom of the discharge curve, rather than the peak that corresponds to the top of the curve. Note that this method of estimation is possible only when no surface runoff is occurring. Daily mean discharges for periods of both significant and minimal ice-effect will be estimated and published in the Annual Water-Data Report for the water year in which they occurred.
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
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.
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