The Lower Susquehanna River Watershed Assessment (LSRWA) report released for public comment yesterday, November 13th 2014, indicates that the reservoir behind the Conowingo Dam is trapping smaller amounts of sediment and has essentially reached its limit to trap in the long term.
However, a large majority of the pollution to the Chesapeake Bay from the Susquehanna River comes from runoff from pollution sources from the upstream drainage area or watershed, as opposed to the sediment and associated nutrients collected behind the dam.
The inter-agency draft report was released by the U.S. Army Corps of Engineers (USACE) and non-federal sponsor the Maryland Department of the Environment (MDE).
Modeling in the report shows that managing sediment through dredging, bypassing or dam operational changes, alone, do not effectively offset the adverse impacts to water quality from the loss of capacity for the dam to trap sediment in the long term. The report suggests that strategies to reduce nutrient pollution at its source from throughout the Bay drainage area are more effective at addressing impacts to the Bay.
“We worked with a team of inter-agency experts, using current scientific information and the best modeling tools available in order to understand the complex relationship between river flow and sediment and ecological resources,” said Col. Trey Jordan, USACE Baltimore District commander. “Our partners undertaking ongoing efforts to restore the Chesapeake Bay and its surrounding watershed are now armed with better science to make decisions to protect water quality, habitat and aquatic life.”
The study area consists of the Lower Susquehanna River Watershed from Sunbury, Penn., to the confluence with the Chesapeake Bay and includes the Holtwood, Safe Harbor, and Conowingo hydroelectric dams located on the lower Susquehanna River.
“This study shows that while the build up of sediment behind the Conowingo Dam does impact water quality in the Bay, following through on the blueprint to clean up the Chesapeake Bay and its tributaries will have a much greater and longer-lasting effect on water quality than addressing the Conowingo Dam problem alone,” said Robert M. Summers, MDE secretary.
For the executive summary, full report with appendices, and associated graphics, and information on how to make a comment click HERE.