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Home Water Data February 2019 Water Conditions Summary Estimated Streamflow to the Chesapeake Bay

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Estimated streamflow entering the Chesapeake Bay is computed on a monthly and annual basis using streamflow measurements from the Susquehanna, Potomac, and James Rivers. Data are presented in tables and graphs, typically grouped by water year — the natural, annual water cycle used by hydrologists. A water year is the 12-month period beginning October 1 and ending September 30. The water year is designated by the calendar year in which it ends and includes 9 of the 12 months. For example, the year beginning October 1, 2017 and ending September 30, 2018, is called “water year 2018.”

The health of the Chesapeake Bay largely is driven by changes in streamflow and the amount of pollution it contains. Runoff in the Chesapeake Bay watershed carries pollutants, such as nutrients and sediment, to rivers and streams that drain to the Bay. Scientists can use estimated streamflow entering the Chesapeake Bay to assess the health of the Bay and make ecological forecasts.

For more information about USGS Chesapeake Bay activities, please visit:

Data and more information on the freshwater streamflow to the Chesapeake Bay can be found here: “Estimated Streamflow Entering Chesapeake Bay

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Page Last Modified: Friday, October 24, 2014