According to the Maryland Department of Natural Resources, 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 which, in turn, could result in less underwater grasses and increased algal blooms. The Maryland Department of Natural Resources (DNR) is expected to 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.
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.
The early spring season is a critical period for underwater grasses, which are beginning to grow. Also affected are saltwater and anadromous fish such as striped bass, yellow perch, river herring and American shad, all of which spawn in the Chesapeake during the Spring.