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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°40’17", long
71°08’59", Essex County, Hydrologic Unit 01070002, on left
bank at upstream side of Balmoral Street bridge, and 3 mi upstream from
mouth at Andover.
DRAINAGE AREA--72.8 mi2.
PERIOD OF RECORD--October 2006 to current year.
GAGE--Data Collection Platform with satellite telemeter. Datum of gage is 34.20 ft above NAVD 1988, estimated from topographic map. Datum previously reported as 35 ft above NGVD 1929, estimated from topographic map.
REMARKS--Flow affected by upstream withdrawals for municipal water supplies of many towns.
COOPERATION BY--Town of Andover.
The precipitation data for this station are temporary and will only be displayed for 120 days. Time series of 15-minute or cumulative daily values WILL NOT be available for retrieval following the 120-display period. Although the instrumentation is calibrated at least once/year, the temporary classification means that documented routine inspections and other quality assurance measures are not performed that would make the data acceptable for archival, retrieval, or future use in general scientific or interpretive studies. The preciptation gage is operated seasonally, from April to November.
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