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Puget Sound Georgia Basin Model

PNNL's Salish Sea Model Achieves a New Milestone - Hypoxia in Salish Sea Reproduced

July 2018

[Left] Salish Sea Model team of coastal ocean modeling specialists at the Marine Sciences Laboratory offices in Seattle, WA (left to right: Jonathan Whiting-Scientist, Adi Nugraha-Scientist, Tarang Khangaonkar-Scientist/Program Manager, Lakshitha Premathilake-Post Doc RA, Wenwei Xu-Scientist, Taiping Wang-Scientist, and Wei Chen WU-Post Doc RA), [Right] Predicted locations with occurrence of hypoxia (DO < 2 mg/L) - Y2014 (see Khangaonkar et al. 2018 for details).

PNNL scientists at the Marine Sciences Laboratory have worked on the development of a comprehensive three-dimensional hydrodynamic and biogeochemical model of the Salish Sea, an intricate, interconnected network of coastal waterways, inlets, bays and estuaries that encompasses southwest British Columbia and the Puget Sound in Washington state. The Salish Sea Model is the first of its kind to successfully simulate estuarine circulation, inter-basin-exchanges, and annual biogeochemical cycles in a single modeling framework in the inner waters of Puget Sound, Georgia Basin, San Juan Islands, and the Northwest Straits. For the scientific community, a key performance measure for acceptance has always been a model's ability to reproduce recurring hypoxia - a condition characterized by low dissolved oxygen levels - and responsiveness to anthropogenic nutrient loads, such as fertilizer and wastewater. An elusive goal that has stymied ecosystem modeling research and nutrient management efforts in the region for decades.

Now, for the first time, the PNNL team's Salish Sea Model has met that milestone, reproducing well-known hypoxia occurrences in Hood Canal, Penn Cove, East Sound, and Henderson Bay (Khangaonkar et al. 2018). In addition, the results show that nutrient loads from land-based sources are responsible for nearly 62 percent of exposure to hypoxic waters in the Salish Sea.

The model has been selected as the tool of choice by the U.S. Environmental Protection Agency (EPA) and Washington State Department of Ecology for developing the Marine Water Quality Implementation Standard (MWQ IS) through the Puget Sound Nutrient Source Reduction Project.

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