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Provisional data for Massachusetts

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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.


Provisional Data Statement

Data are provisional and subject to revision until they have been thoroughly reviewed and received final approval.

Real-time data relayed by satellite or other telemetry are automatically screened to not display improbable values until they can be verified.

Provisional data may be inaccurate due to instrument malfunctions or physical changes at the measurement site. Subsequent review based on field inspections and measurements may result in significant revisions to the data.

Data users are cautioned to consider carefully the provisional nature of the information before using it for decisions that concern personal or public safety or the conduct of business that involves substantial monetary or operational consequences.

Information concerning the accuracy and appropriate uses of these data or concerning other hydrologic data may be obtained from the USGS.