Structured Decision Making to Meet a National Water Quality Mandate.

Water quality criteria are necessary to ensure protection of ecological and human health conditions, but compliance can require complex decisions. We use structured decision making to consider multiple stakeholder objectives in a water quality management process, with a case study in the Three Bays watershed on Cape Cod, Massachusetts. We set a goal to meet or exceed a nitrogen load reduction target for the watershed and four key objectives: minimizing economic costs of implementing management actions, minimizing the complexity of permitting management actions, maximizing stakeholder acceptability of the management actions, and maximizing the provision of ecosystem services (recreational opportunity, erosion and flood control, socio-cultural amenity). We used multi-objective optimization and sensitivity analysis to generate many possible solutions that implement different combinations of nitrogen-removing management actions and reflect tradeoffs between the objectives. Results show that technological advances in controlling household nitrogen sources could provide lower cost solutions and positive impacts to ecosystem services. Although this approach is demonstrated with Cape Cod data, the decision-making process is not specific to any watershed and could be easily applied elsewhere.