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September Water Conditions Above Normal in Maryland, Delaware, and D.C.

U.S. Department of the Interior
U.S. Geological Survey

Wendy McPherson (
Maryland-Delaware-D.C. Water Science Center
5522 Research Park Drive
Baltimore, MD 21228
FAX: (443)498-5510

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Updated: October 9, 2000

Streamflow and Groundwater levels in the Maryland-Delaware-D.C. region were above normal or in the upper part of the normal range for September, according to hydrologists at the U.S. Geological Survey (USGS) in Baltimore, Maryland. Average streamflow for several key sites ranged from 125 to 827 percent of the long-term average discharge.

Average streamflow into the Chesapeake Bay was 25 billion gallons per day (bgd), which is 21 percent above the long-term average for September. The Susquehanna and Potomac Rivers provided 49 percent of the total streamflow to the Chesapeake Bay, discharging 6.7 bgd and 5.5 bgd, respectively.

For the 2000 water year (October 1999 through September 2000), the average monthly inflow to the Chesapeake Bay was 45 bgd, which is 53 percent more than the 1999 water year (29 bgd). The water year begins October 1 each year and is used by hydrologists because it is the time when streamflows are generally lowest across the nation. Groundwater levels and soil moisture levels are also low then, because the replenishing rains of autumn usually have not begun.

Streamflow at the Potomac River near Washington, D.C. averaged 4.0 bgd, which is 111 percent above normal for September. Although streamflows increased 54 percent over the last water year from 3.7 bgd in 1999 to 5.7 bgd in 2000, the long-term streamflow average is 20 percent below the normal flow for the years of record.

Groundwater levels at the end of September remained in the normal to above-normal range in western and southern Maryland and in the normal range elsewhere in Maryland and Delaware. Monthly updates of Groundwater conditions for 32 key observation wells that encompass all counties of Maryland and Delaware can be found at

Water storage in the Baltimore reservoir system increased during September to 67.89 billion gallons (89 percent of capacity).

In-depth information about USGS programs may be found on the USGS home page at and for Chesapeake Bay activities. To receive the latest USGS news releases automatically by e-mail, send a request to Specify the listserver(s) of interest from the following names: water-pr; geologic-pr; hazards-pr; biological-pr; mapping-pr; products-pr; lecture-pr. In the body of the message write: subscribe (name of listserver) (your name). Example: water-pr joe smith.

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In-depth information about USGS programs may be found on the USGS home page at and for Chesapeake Bay activities.

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