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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°22’43.3", long
71°13’20.5", Middlesex County, Hydrologic Unit 01090001, on
left bank, 50 ft downstream from Linden St, and about 0.5 mi upstream
from mouth at Charles River.
DRAINAGE AREA--11.3 mi2.
PERIOD OF RECORD-- March 2014 to current year.
GAGE--Water-stage recorder with satellite telemeter. Elevation of gage is 35 ft above North American Vertical Datum, 1988, from digital map.
COOPERATION BY-- Massachusetts Department of Conservation and Recreation, Division of Engineering and Planning.
REMARKS--Discharge record highly provisional above 50 ft2/sec during development of the stage-discharge rating.
ICE EFFECTS ON STREAMFLOW During winter, ice formation in streams can cause stage and corresponding discharge values to appear higher than expected during periods of no precipitation. Ice effects from partial ice cover or shore ice may be minor, where stage and discharge appear to increase at night and decrease to base-line conditions around midday for one or more days. Major ice effects from complete ice cover appear as constantly increasing stage and discharge over several days during prolonged cold periods. Stage and discharge values for streams experiencing minor ice effects will continue to be displayed on the web to enable the user to estimate the approximate base-line discharges. Note that this method of estimation should only be used when no runoff occurs. During periods of major ice effects, display of discharge data on the web will be temporarily discontinued to prevent misuse of erroneous discharge data. The discharge record will resume when it is determined that ice conditions are no longer present. Display of stage data during periods of minor and major ice effects will continue to be displayed on the web. Daily mean discharges will be estimated for all periods of ice-effected discharges.