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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°46’22", long
71°04’59", Essex County, Hydrologic Unit 01070002, on left
bank upstream from Rt 125 bridge at Haverhill.
DRAINAGE AREA--4,850 mi2 of which 214 mi2 probably is noncontributing.
PERIOD OF RECORD--July 2006 to current year.
GAGE--Data Collection Platform with satellite telemeter. Gage height readings are set to National Geodetic Vertical Datum of 1929.
REMARKS--Stage affected by tidal fluctuations. Intake out of water at stages below approximately -0.30 ft.
COOPERATION BY--Massachusetts Department of Conservation and Recreation, Office of Water Resources.
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