The second Bay Journal article (2018-10-16) in a special series looking at the Chesapeake Bay reported that the Chesapeake Bay Program is working on revising the pollution reduction targets for nitrogen and phosphorus under the Bay Total Maximum Daily Load (TMDL). The revisions are based on better information and computer modeling. Once the new targets are finalized, states must update their watershed implementation plans by August of 2019 to show how they and their local governments will meet these new goals.
The revised computer model found that Bay watershed states were only 30 percent toward meeting their 2025 nitrogen target (the previous computer model found the states had achieved a 36 percent reduction. The downgrade was based on a finding that fewer nitrogen reductions than previously estimated were coming from non-wastewater sources.
From the article:
The model analysis further incorporates refined information about the importance of where nutrients are generated. Nutrient runoff that occurs closer to major rivers, for example, tends to have more influence than runoff near smaller rivers because major rivers transport nutrients to the Bay more effectively. …
In addition, the relative impact of nitrogen is greater than phosphorus in the new modeling.
Overall, the new model findings had the greatest impact on Maryland. In the old model, the state needed to achieve 5.7 million additional pounds of nitrogen reductions to meet its 2025 goal; in the new model it has to achieve 8.4 million pounds of reductions.
The article also cautioned that several important pollution sources still need to be addressed, including: (1) the Conowingo Dam; (2) climate change; and (3) the James River in Virginia. Sediment goals also need to be revised but the model assumes phosphorus controls will also control sediment.
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