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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°30’45", long
71°24’17", Middlesex County, Hydrologic Unit 01070005,
river-level sensor on right bank, 15 ft above footbridge, 500 ft
downstream from old millpond and dam at North Acton, 2.2 mi northeast
of Acton, and 5 mi upstream from mouth at Assabet River at West
DRAINAGE AREA--12.8 mi2.
PERIOD OF RECORD--Discharge: July 1963 to current year.
GAGE--Data Collection Platform with satellite telemeter. Datum of gage is 154.19 ft above NAVD 1988, estimated from topographic map. Datum previously reported as 155 ft above NGVD 1929, estimated from topographic map. Prior to Jan. 8, 1997, at site 1,000 ft downstream, at same datum.
COOPERATION BY--Massachusetts Department of Conservation and Recreation, Office of Water Resources.
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