News from the DNR Office of Communications

Heavy Rains, Snowmelt May Affect Chesapeake Bay Health

DNR Continuing to Monitor for Bay Impacts

Annapolis, Md. (March 21, 2011) — Early March runoff into the Susquehanna River watershed from heavy rains and snowmelt has brought a flood of nutrients and sediment-laden freshwater flowing into the Chesapeake Bay. This heavy spring runoff has resulted in record low water clarity for the month of March in many areas of Maryland’s portion of the Chesapeake Bay. Continued wet spring weather could extend these high flows that might result in less underwater grasses and an increase in algal blooms. The Maryland Department of Natural Resources (DNR) will continue its comprehensive Chesapeake Bay water quality habitat and living resources monitoring to assess any short- or long-term storm-related impacts.

On March 12, 2011, two days after a very heavy rain event (2+ inches) across the region, the U.S. Geological Survey (USGS) recorded a peak “flow” of 485,000 cubic feet/second (cfs) from the Susquehanna River at Conowingo Dam. Average monthly flows at that site in March are about 75,000 cfs. This is the highest average daily flow rate observed at the dam since floodwaters from Tropical Storm Ivan passed in September 2004 (496,000 cfs on September 19; 545,000 cfs on September 20.)

A review of 26 years of water clarity data collected by the State shows that depth measurements in the Chesapeake Bay and many tributaries in March 2011 are below historic measures or set new historic lows.

A high amount of freshwater flowing into the Chesapeake Bay erodes sediments and transports polluted runoff (including nutrients and sediments) downstream towards the Bay. Generally, short-term storms will have short-term impacts on the Bay, but, if wet weather continues, there could be long-term consequences for the Bay’s water quality, and its abundant plant and animal population, as well.

The late winter/early spring season is a critical period for many aquatic species such as the underwater grasses, which are beginning to grow and the many types of fish, which are beginning to spawn. Full storm impacts may not be known until mid-summer or later.

Even with the surges in precipitation, Maryland is committed to reducing polluted runoff in order to meet Chesapeake Bay water quality goals. In May 2009, along with Pennsylvania and Virginia, Maryland agreed to aggressive 2-year milestones for assuring accountability in limiting nutrients and sediments entering the Bay. This requires citizens, businesses, and local, state and federal governments to work together in efforts to reduce polluted runoff by planting cover crops to reduce runoff from farms, reducing runoff from urban areas, restoring natural filters and conserving high priority lands.

Full story is available at

For More Information
Real-time Maryland Tidal Water Quality Conditions
Restoring the Chesapeake Bay: Maryland’s Actions and Progress
What You Can Do to Help the Bay
US Geological Survey - Daily streamflow conditions in Maryland:

   March 21, 2011

Contact: Josh Davidsburg
410-260-8002 office I 410-507-7526 cell

The Maryland Department of Natural Resources is the state agency responsible for providing natural and living resource-related services to citizens and visitors. DNR manages nearly one-half million acres of public lands and 17,000 miles of waterways, along with Maryland's forests, fisheries and wildlife for maximum environmental, economic and quality of life benefits. A national leader in land conservation, DNR-managed parks and natural, historic and cultural resources attract 11 million visitors annually. DNR is the lead agency in Maryland's effort to restore the Chesapeake Bay, the state's number one environmental priority. Learn more at