USGS - science for a changing world

Water Science for Maryland, Delaware and the District of Columbia

Home >> Publications >> Press Release

Streamflow and Groundwater Levels High in May

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

Jump to archives >>

Updated: June 4, 2003

A very rainy May led to above normal streamflow and groundwater levels in many streams and wells across Maryland and Delaware, according to hydrologists at the U.S. Geological Survey (USGS) in Baltimore. Groundwater levels were above normal in all but three of the wells used by the USGS to monitor climatic conditions in the bi-state region for May. Streams across the region were also flowing above normal and some have set new daily high and monthly records.

Cool temperatures and slow-moving storms caused persistent rainfall in during May 2003 that led to an extremely wet month. May 2003 was the wettest month since September 1999, when tropical storm Floyd engulfed the region, according to the National Weather Service. It was the sixth wettest May for Washington, D.C. and the seventh wettest May for Baltimore.

For news release and images, visit:

Groundwater levels are expected to drop during the growing season because of increased demand, but the abundant rainfall has raised groundwater levels, recharged the aquifers, and saturating the soil, making it difficult for farmers. Wells in Charles and Queen Annes Counties, Maryland set monthly high records. This is a large contrast to 2002, a drought year, when eight wells were setting monthly low records. For 5-year hydrographs of groundwater levels, visit:

Streamflow levels have also been above normal across Maryland and Delaware at the end of May. With groundwater and streamflow levels already high, there is the potential for localized flooding. The average monthly streamflow at the Potomac River near Washington, D.C. was 22.0 bgd (billion gallons per day), or 132 percent above normal (see graphs at Streamflow data can be monitored on the web at Five-year monthly streamflow hydrographs can be viewed on the USGS website at

Total flow into the Chesapeake Bay during May averaged 87 bgd (billion gallons per day), which is 36 percent above average. For the first 5 months of this year, the flow into the Bay has averaged 92.1 bgd, which is about twice the amount the first 5 months of last year (45.8 bgd). Average flow for the 5-month period was 76.4 bgd, resulting in 20 percent more total flow than average. During the drought over the past 2 years, water clarity conditions in the Bay have improved because less nutrients and sediment were flowing into the Bay. Conditions have changed this spring because of increased flow. The graph below shows the total flow into the Chesapeake Bay at different locations along the Bay (see The dashed line shows the monthly mean inflow. There were several months below normal during the drought years of 2001 and 2002. In 2003, the total flow has been above average.

The possible consequences of increased streamflow into the Bay include degraded water-quality conditions in the spring and summer as larger amounts of nutrients and sediment are carried into the Bay. Higher nutrient levels lead to algal blooms, which can decrease the amount of dissolved oxygen in the Bay and result in fish kills. The algal blooms, along with increased amounts of sediment, can cause a decrease in the light needed by the underwater grasses in the Bay. The grasses are important habitat for crabs and food for waterfowl. More information about water quality and the Chesapeake Bay can be found at

Streamflow and groundwater levels are used to gauge water conditions and may be used to predict the potential for flooding and drought conditions. These USGS data have been provided to State and local water resource managers and are critical for making appropriate decisions on water restrictions. For more information on streamflow and groundwater levels in Maryland and Delaware, see Water Watch at: Water Watch.

Five-year streamflow hydrographs can now be viewed at:

Groundwater Levels in the Metropolitan Washington D.C. Area can be seen at

The USGS, a bureau within the Department of the Interior, is the Nation's largest water, earth and biological science, and civilian mapping agency providing 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.

** * USGS * * *

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

Archived News Releases 2000-Present








Accessibility FOIA Privacy Policies and Notices

Take Pride in America logo logo U.S. Department of the Interior | U.S. Geological Survey
Page Contact Information:
Page Last Modified: Thursday, September 14, 2017