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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° 25’55", long 71°
27’01", Middlesex County, Hydrologic Unit 01070005, on right
bank at Maynard, 150 ft upstream from bridge on State Highway 27, 1.7
mi downstream from Assabet Brook, and 7.1 mi upstream from confluence
with Sudbury River.
DRAINAGE AREA--116 mi2.
PERIOD OF RECORD--Discharge: July 1941 to current year.
Water-quality records: Water years 1954, 1967–74.
REVISED RECORDS--WSP 1231: 1945–46.
GAGE--Data Collection Platform with satellite telemeter. Datum of gage is 141.33 ft above NAVD 1988. Datum previously reported as 142.12 ft above NGVD 1929.
REMARKS--Occasional diurnal fluctuation at low flow by mills upstream; greater regulation prior to 1969. Since 1962, high flow affected by retarding reservoirs and, since 1970, occasional release at low flow by these reservoirs.
COOPERATION BY--Massachusetts Department of Conservation and Recreation, Office of Water Resources.
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