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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°39’35", long
70°53’39", Essex County, Hydrologic Unit 01090001, on left
bank 200 ft downstream from Willowdale Dam, 1.5 mi downstream from
Howlett Brook, and 4 mi upstream from Ipswich.
DRAINAGE AREA--125 mi2.
PERIOD OF RECORD--Discharge: June 1930 to current year.
Water-quality records: Water years 1954, 1976–79.
REVISED RECORDS--WSP 1621: 1930–58 (monthly runoff). WDR MA-RI-84-1: drainage area.
GAGE--Data Collection Platform with satellite telemeter. Datum of gage is 20.63 ft above National Geodetic Vertical Datum of 1929.
REMARKS--Diversions upstream for municipal supply of Reading, Lynn, Peabody, Danvers, Salem, and Beverly. Occasional regulation by dams and reservoirs upstream.
COOPERATION BY--Massachusetts Department of Conservation and Recreation, Office of Water Resources.
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