The Chesapeake Bay TMDL 2017 Midpoint Assessment

The Chesapeake Bay Program established the historic Chesapeake Bay Total Maximum Daily Load (TMDL) in 2010 which set nitrogen, phosphorous, and sediment limits in the Chesapeake watershed and airshed. All pollution control practices are expected to be implemented to restore the Bay by 2025. An assessment in 2017 was called for to review the progress toward load reductions identified by the 2010 TMDL. The 2017 Midpoint Assessment identified three main priorities: 1) Phase III Watershed Implementation Plan (WIP) development to guide pollution management implementation annually until 2025, 2) an assessment of reservoir infill from the Conowingo Dam which was increasing pollutant loads to the Chesapeake, and 3) accounting for climate change impacts on Chesapeake water quality. The 2017 TMDL Midpoint Assessment provided nutrient targets for the Phase III Watershed Implementation Plans (WIPs) for Maryland, Delaware, New York, Pennsylvania, West Virginia, District of Columbia, and Virginia. In addition, it was determined that the net Conowingo reservoir trapping capacity has reached dynamic equilibrium and that the resulting decrease in Conowingo nutrient trapping impacts the Bay TMDL restoration. The Midpoint Assessment called for a detailed plan incorporating the Conowingo planning target with a separate WIP framework. The third Midpoint Assessment priority of accounting for the impacts of a changing climate on Chesapeake Bay water quality and living resources determined that an initial estimate of an additional 9 million pounds of nitrogen and 0.5 million pounds of phosphorous due to climate change that needed to be accounted for. Additional work will conclude in 2019 which will refine the estimated nutrient reductions needed to be addressed from climate change in the Chesapeake.