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Structured Decision Making to Meet a National Water Quality Mandate
Citation:
Martin, D., A. Piscopo, Marty Chintala, T. Gleason, AND W. Berry. Structured Decision Making to Meet a National Water Quality Mandate. JAWRA. American Water Resources Association, Middleburg, VA, 55(5):1116-1129, (2019). https://doi.org/10.1111/1752-1688.12754
Impact/Purpose:
This paper is the second in a series of two articles to describe a decision-focused process for coastal resource planning and management. In this article, we aim to solve the problem of meeting a water quality mandate while satisfying community-level objectives. We partnered with a local non-profit organization in the Three Bays watershed, Cape Cod, Massachusetts, to collect and model the costs and benefits of implementing many watershed management strategies to meet a nitrogen load reduction target. Our research resulted in developing many different solutions to the problem. Each solution meets the nitrogen load reduction target but with tradeoffs in how much each solution costs and its benefits in terms of permitting complexity, public acceptability, and impact on ecosystem services. Using the results, we guided our partners in understanding these tradeoffs in what could be gained (or lost) by implementing different combinations of management strategies to meet the nitrogen load reduction target in the watershed. This decision-aiding process resulted in stakeholder-driven goals, clear articulation of management objectives, and transparency in the metrics and models we used throughout the research process.
Description:
National water quality standards determine limits to a water quality pollutant that are necessary to ensure protection of ecological and human health conditions. In this article, we apply a structured decision making process to guide watershed managers in meeting national water quality standards while satisfying community-level objectives. Our approach is based on a nitrogen management case study in the Three Bays watershed on Cape Cod, Massachusetts. We partnered with a non-profit watershed management organization to identify objectives and performance metrics for implementing several management actions associated with nitrogen abatement to meet a total maximum daily load for nitrogen into the watershed. Key objectives for this research included minimizing costs, minimizing permitting complexity, maximizing public acceptability, and maximizing the provision of ecosystem services. We used a multi-objective evolutionary algorithm to generate optimal management solutions that reflect the tradeoffs between these objectives while achieving the nitrogen mandate. Two sets of optimal solutions were generated based on two alternative planning scenarios that reflected the current projected performance of an innovative household septic system design and the anticipated future performance, pending technological advances in the design that are currently being tested. We analyzed the sets of optimal solutions by visualizing the results with our collaborators and discussing tradeoffs between the objectives and the quantity of management actions chosen in each scenario. Results show that technological advances in controlling household nitrogen sources on Cape Cod could provide lower cost solutions to meet the nitrogen load reduction target and better overall impacts to ecosystem services. Our approach is generally applicable as a complement to current methods for decision-focused water quality management in coastal watersheds.
