New report released for public comment analyzes sediment and pollution flow impacts to Chesapeake Bay from watershed, Conowingo Dam – names watershed-wide reduction strategies as key

Published Nov. 13, 2014

The Lower Susquehanna River Watershed Assessment (LSRWA) report released for public comment, Nov. 13, 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).

Another major finding of the draft report indicates that nutrients that enter the river upstream of the dams and attach to particles of sediment and then flow downstream to the Bay have a bigger impact on water quality than the sediment, itself. Nutrient pollution has a lingering effect that leads to algae blooms and dead zones that have the potential to suffocate and stress marine life. The report includes consideration of management strategies, and recommendations for future opportunities. View the executive summary, full report with appendices, and associated graphics, and information on how to make a comment at

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.

The report underwent multiple peer reviews, including an independent, scientific peer review sponsored by the Chesapeake Bay Program partnership’s Scientific and Technical Advisory Committee.

“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. Much of the modeling efforts were focused on the Conowingo Dam, as it is the largest dam and reservoir closest to the Chesapeake Bay with remaining capacity left to trap sediment.

"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. "Addressing the sediment behind the dams is part of the complete solution needed to restore the Bay and its tributaries, as is the work that upstream states are doing to reduce pollution in the first place. But we will not meet our Bay restoration goals without following through on our efforts to control pollution from Maryland and the rest of the watershed as well."

Major recommendations in the report include quantifying the full impact on Chesapeake Bay water quality and living resources based on new understandings in the report; integrating findings from the report into ongoing analyses and development of watershed implementation plans as part of the Chesapeake Bay Total Maximum Daily Loads assessments; developing and implementing management options that offset impacts to the upper Chesapeake Bay ecosystem from increased sediment-associated nutrient loads; and committing to enhanced long-term monitoring and analysis of sediment and nutrient processes in the watersheds to promote adaptive management into the future.

A public comment period on the draft report is now open until Jan. 9, 2015. Interested parties can submit comments via:

-       E-mail to

-       Letter postmarked by Jan 9, 2015, to: U.S. Army Corps of Engineers, Baltimore District, Attn: Anna Compton , P.O. Box 1715, Baltimore, MD 21203.

-        A public meeting and webinar held Dec. 9 at Harford Community College in Bel Air, Md., from 7 – 9 p.m. Details on the public meeting and log-in information for the webinar will be posted on the website, as well as other meeting materials.

Once the comment period closes and comments have been addressed, as appropriate, a final report anticipated for summer 2015 will be published to better inform stakeholders undertaking efforts to restore the Chesapeake Bay.

The LSRWA inter-agency team is comprised of the USACE Engineering Research and Development Center, U.S. Geological Survey, Susquehanna River Basin Commission, Nature Conservancy, Chesapeake Bay Program, Maryland Department of Natural Resources, and Maryland Geological Survey.

The intent of this report was to analyze the movement of sediment and associated nutrient loads and impacts within the lower Susquehanna watershed to the upper Chesapeake Bay.

LSRWA directly contributes to Executive Order 13508 goals to restore clean water, recover habitat, and sustain fish and wildlife; and was authorized by Section 729 of the Water Resources Development Act of 1986, as amended. The total cost of the study is approximately $1.38 million. Funding was received in 2009, and after scoping and partnership agreements laid the groundwork, the assessment began in 2011.


Additional media contacts for LSRWA team partners:

Jay Apperson, MDE, 410-537-3003,

Kristen Peterson, Maryland DNR, 410-260-8002,

Margaret Enloe, Chesapeake Bay Program Partnership, 410-267-5740,



Sarah Gross

Release no. 111314-001