Publication Summary

This is the plan for the Puget Sound Dissolved Oxygen Modeling Study: Intermediate-scale Model Development.

The Washington State Department of Ecology (Ecology) is developing an intermediate-scale mathematical model for the entire Puget Sound estuary system to further our understanding of processes that affect dissolved oxygen. This project will help determine (1) if current and potential future nitrogen loadings from point and nonpoint sources into Puget Sound are significantly impacting water quality at a large scale and (2) what level of nutrient reductions are necessary to reduce or eliminate human impacts to dissolved oxygen levels in sensitive areas.

The northern boundary will be set at the entrance to Johnstone Straits past the Fraser River north of Vancouver B.C. The model resolution will be finer than the large-scale box model, being developed by Ecology in tandem with this model, ensuring reasonable representation of the various subbasins within Puget Sound.

The model will simulate full eutrophication kinetics. Nutrient (nitrogen) loads will be specified as input variables for all important sources. The objective of this intermediate-scale hydrodynamic and water quality model is to develop a large-scale understanding of the nutrient assimilation capacity of Puget Sound. The preference is to develop the water quality model in a de-coupled configuration so that it may be applied repeatedly using previously computed hydrodynamic solutions. The water quality model will be calibrated using data collected in Puget Sound during 2006 and will be used to simulate the effects of alternative nutrient-loading scenarios.

Each study conducted by Ecology must have an approved Quality Assurance Project Plan. The plan describes the objectives of the study and the procedures to be followed to achieve those objectives. The final report will be subject to formal internal and external review, and the entire project will be evaluated through an independent third party model audit process. After completion of the study, the final report describing the study results will be posted to the Internet.