The cost-effectiveness of total maximum daily load (TMDL) programs depends heavily on program design. We develop an optimization framework to evaluate design choices for the TMDL for the Potomac River, a Chesapeake Bay sub-basin. Scenario results suggest that policies inhibiting nutrient trading or offsets between point and nonpoint sources increase compliance costs markedly and reduce ecosystem service co-benefits relative to a least-cost solution. Key decision tradeoffs highlighted by the analysis include whether agricultural production should be exchanged for low-cost pollution abatement and other environmental benefits and whether lower compliance costs and higher co-benefits provide adequate compensation for lower certainty of water-quality outcomes.

The application of manure phosphorus at rates above crop uptake has resulted in water pollution for some regions. In response, new manure management standards will require some farms to match manure phosphorus application rates with crop uptake. For some regions, this will lead to more crop acres and a shift toward crops with greater nutrient uptake, both of which will increase nitrogen runoff. The greater nitrogen runoff could offset the lower phosphorus runoff to result in greater water pollution. This demonstrates the law of unintended consequences, which results when policy does not consider how economic agents respond to incentives.