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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 42o22'08", long
71o16'16", Middlesex County, Hydrologic Unit
01090001, 200 ft downstream of State Highway 20, 1,000 ft upstream from
Stony Brook Reservoir, and 1.8 mi west of Waltham.
DRAINAGE AREA--22.0 mi2.
PERIOD OF RECORD--October 1997 to September 1998; August 2002 to current year.
GAGE--Data Collection Platform, water-temperature, specific conductance, pH, and turbidity water-quality monitor, with telephone telemeter. Datum of gage is 89.20 ft above NAVD 1988, estimated from topographic map. Datum of gage previously reported as 90 ft above NGVD 1929, estimated from topographic map.
REMARKS--Flow affected by regulation of dam 2.6 mi upstream on Hobbs Brook at outflow of Cambridge Reservoir.
COOPERATION BY--Cambridge Water Department
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Value May 25