Publication Summary

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

The Washington State Department of Ecology (Ecology) is developing a large-scale computer model for the entire Puget Sound estuary system to further our understanding of processes that affect dissolved oxygen (DO). The hydrodynamic and water quality components will be built using existing tools in the form of the Babson/Kawase/MacCready Puget Sound box model as modified by Ecology (BKM-ECY) and the Environmental Protection Agency′s Water Quality Analysis Simulation Program (WASP7), respectively.

The calibrated model will evaluate water quality conditions observed in Puget Sound from 1999 – 2008 and simulate the effects of alternative nutrient-loading scenarios. This project is part of a larger effort to determine (1) if current 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 DO levels in sensitive areas.

The BKM-ECY box model conceptualizes Puget Sound as a series of 10 subbasins, each with a single surface and deep layer allowing for estuarine circulation. While the spatial resolution of this model is coarse, it will be computationally efficient and allow for rapid evaluation of multiple nutrient-loading scenarios. The large-scale model will be used as a screening-level tool to support an intermediate-scale modeling effort being conducted in tandem with this project, and as a community tool for other purposes. The intermediate-scale model will have much finer spatial resolution and an expanded geographic domain. However, much of the freshwater and nutrient-loading information will be used by both modeling efforts.

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. After completion of the study, a final report describing the study results will be posted to the Internet.