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1999 Flow Into Chesapeake Bay Lowest Since 1960s Drought

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: January 6, 2000

Streamflow into the Chesapeake Bay for the year 1999 was the fourth lowest annual flow for the period 1951-1999, according to hydrologists at the U.S. Geological Survey (USGS) in Baltimore, Maryland. Annual flow into the Bay for the past 49 years has averaged about 50.2 billion gallons per day (bgd). Flow for 1999 was estimated by USGS hydrologists at 34.6 bgd, or 31% below average. Only 1963, 1965, and 1966 had lower flows at 33.8, 31.6, and 34.4 bgd, respectively. Cumulative streamflow into the Chesapeake Bay is estimated by using data collected by the USGS near the end of each month from index stations on the Susquehanna, Potomac, and James Rivers.

According to the Cheasapeake Bay Program, the low-flow conditions resulted in higher salinity levels in the Bay and lower dissolved oxygen in the creeks feeding the Bay. The higher salinity caused oysters to suffer because of a greater incidence of the diseases Dermo and MSX, which are favored in higher salinity years. The lower dissolved oxygen resulted in fishkills in the upper parts of the tidal tributaries including the Magothy River, Pocomoke River, and creeks draining into the Baltimore Harbor. More information can be found on the Chesapeake Bay Program's website at

Flow returns to normal lately

Recently, streamflow for the month of December increased from November at index stations throughout Maryland and Delaware, and remains in the normal range. Contents of the Baltimore reservoir system increased from 57,640 million gallons (57.64 billion gallons) in November to 61,320 million gallons near the end of December, which was 85 percent of average and 97 percent of December 1998. However, Groundwater levels at the end of December have decreased and remain in either the normal or below normal range throughout most of Maryland. Eastern Shore Groundwater levels fell slightly and remain in the below normal range.

As the nation's largest water, earth and biological science, and civilian mapping agency, the USGS works in cooperation with more than 2,000 organizations across the country to provide reliable, impartial scientific information to resource managers, planners, and other customers. This information is gathered in every state by USGS scientists to minimize the loss of life and property from natural disasters, contribute to the sound conservation and the economic and physical development of the nation's natural resources, and enhance the quality of life by monitoring water, biological, energy, and mineral resources.

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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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