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Cold, Dry January Leads to Drop in Water Levels

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: February 5, 2004

Streamflow and groundwater levels have dropped from their high levels and many water levels in many streams are now in the normal range across Maryland and Delaware, according to hydrologists at the U.S. Geological Survey (USGS). These declines have also reduced the flow into the Chesapeake Bay. Streamflow has decreased because of the lack of precipitation and the cold temperatures during January. Since the ground is frozen, the snow and water frozen in the ground holds water in storage that will be released when the temperatures are above freezing for an extended period

Chesapeake Bay

Monthly mean streamflow into the Chesapeake Bay during January averaged 60.9 bgd (billion gallons per day), which is only 6 percent above average. Flow to the Bay has been above average since March 2003, with several months with near record-setting high levels. The abundant flow has contributed to higher amounts of nutrients and sediment entering the Bay.

The findings of the USGS Chesapeake Bay Groundwater study have been summarized in a fact sheet “The Influence of Groundwater on Nitrogen Delivery to the Chesapeake Bay, Online Publication - FS-091-03” and a comprehensive technical report “Residence Times and Nitrate Transport in Groundwater Discharging to Streams in the Chesapeake Bay Watershed, Water-Resources Investigations Report 03-4035”. More information about USGS studies to help with the protection and restoration of the Chesapeake Bay and its watershed can be found at


Snowfall in January resulted in only 1.26 inches of water in Baltimore, Maryland, which is 2.21 inches below normal, according to the National Weather Service. Temperatures were also 4.8 ?F colder than normal, averaging 27.5?. Only seven days had temperatures above freezing. The cold temperatures cause water in the soil to freeze, and the water (as ice) is essentially held in storage until it melts and either recharges aquifers or contributes flow to streams.

Status of Streams and Wells for December 2003

The map to the right shows the wells and streams used by the USGS to monitor water conditions in Maryland, Delaware, and Washington, D.C. In January, all wells were at above normal levels (dark circles). A well in Prince Georges County, Maryland was at its highest January level in 40 years (represented by an asterisk).

Streamflow was at normal levels for most streams. Since the region recovered from the drought last winter, water levels in most of these streams and wells had frequently been at above normal levels.


Streams across Maryland and Delaware were flowing at normal to above normal levels in January after several months of above normal flow. Streamflow data in January may have been affected by ice build-up at the gaging stations. Five-year monthly streamflow hydrographs from the USGS stream-gaging network can be viewed on the USGS website at Current and historical streamflow data can be monitored on the web at:

Daily streamflow on the Potomac River near Washington, D.C. in January averaged 7.6 bgd, which is 16 percent below normal for January. More information on the Potomac River is available at:

Groundwater-Unconfined or Shallow Aquifers

Groundwater levels in most of the wells used by the USGS to monitor unconfined or shallow aquifer response to climatic conditions in the bi-state region dropped during January. Although many water levels dropped in January, a well in Prince Georges County, Maryland, was at its highest January level in 40 years. This is the fifth consecutive month of record-setting high groundwater levels for Prince Georges County. For 5-year hydrographs of groundwater levels for the climatic indicator wells, visit:

Water levels are expected to rise as groundwater resources are recharged through the winter and spring months when most plants are dormant and temperatures are lower. Generally, recharge is suspended when the ground freezes and resumes when the temperatures rise above freezing

Groundwater-Confined or Deep Aquifers

Although water is plentiful at the surface (streams, reservoirs, and shallow groundwater reserves are full), some of the deep confined aquifers used for water supply by many people living in southern and eastern Maryland and Delaware continue to decline. The water levels continue to decline because they are being pumped at rates higher than deep groundwater is recharged and since the confined aquifers are deep, water levels in confined aquifers take longer to respond to climatic conditions than shallow aquifers. Confined aquifer wells are measured monthly and can be viewed at:

Reservoir Storage

High groundwater levels and above normal streamflow and rainfall helped to keep reservoir storage levels in the Baltimore reservoir system at capacity in January. Storage in the Triadelphia and Duckett Reservoirs on the Patuxent River has decreased to 95 percent of capacity.

USGS 125th Year Anniversary: Successor to Lewis and Clark

The Lewis and Clark Expedition was the first of many Government surveys of natural resources in the American West. The U.S. Geological Survey was established on March 3, 1879 in response to a report from the National Academy of Sciences, which had been asked by the Congress in 1878 to provide a plan for surveying and mapping the Territories of the United States that would secure the best possible results at the least possible cost. The USGS continues to serve the Nation as an independent fact-finding agency that provides scientific understanding about natural-resource conditions, issues, and problems. Because of its origin in natural resource surveys and the similarity of the USGS mission to Thomas Jefferson’s charge to Meriwether Lewis, the USGS can be seen as the organizational successor to Lewis and Clark. For more information, visit

USGS Water Monitoring

The USGS has been collecting national streamflow data for 120 years, or since 1884. Streamflow and groundwater levels are used to assess the current water conditions and can 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 regulation. For more information on streamflow and groundwater levels in Maryland, Delaware, and Washington, D.C., visit Water Watch at: Water Watch.

The real-time streamflow stations used in this analysis are operated in cooperation with the Maryland and Delaware Geological Surveys, the Maryland State Highway Administration, the U.S. Army Corps of Engineers, the Maryland Department of Natural Resources, the Maryland Department of the Environment, Baltimore County, Baltimore City, and other agencies. The observation wells used in this analysis are operated in cooperation with the Maryland and Delaware Geological Surveys. The real-time wells are operated in cooperation with the Maryland and Delaware Geological Surveys, the Interstate Commission on the Potomac River Basin, and Calvert County, Maryland. The USGS publishes data for 137 streamflow stations and 379 observation wells across Maryland and Delaware.

The USGS serves the Nation by providing reliable scientific information to describe and understand the Earth; minimize loss of life and property from natural disasters; manage water, biological, energy, and mineral resources; and enhance and protect our quality of life.

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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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