AQUA TERRA Consultants
AQUA TERRA Services
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Watershed Modeling Services for King County, Washington

Client: King County Department of Natural Resources, Seattle, WA

The King County Department of Natural Resources, Water and Land Resources Division retained AQUA TERRA Consultants to provide water resources modeling services to develop a water quantity and quality analysis models for two topographic basins - the Green-Duwamish and the Lake Washington-Ship Canal watersheds. These models support the two major projects, the Green-Duwamish Water Quality Assessment (GD WQA) and the Sammamish-Washington Analysis and Modeling Program (SWAMP). They are integrated components of an overall modeling system of both watersheds and major receiving water processes including hydrodynamics, water quality, and bio-dynamics within the Duwamish River and Lakes Sammamish, Washington, and Union.

The primary purpose of the watershed water quality and quantity models are to support the GDWQA and SWAMP teams by simulating at a tributary level, surface and subsurface flow and associated physical, chemical, and biological loads to major receiving waters - the Green River (excluding areas above the Tacoma Public Works Division) and Duwamish Estuary for the GDWQA and the Lakes for the SWAMP under a range of land use and infrastructure scenarios. Additional purposes of these models are to provide a general tool for watershed analysis, management and educational outreach components of SWAMP and GDWQA, King County’s ESA-response, aquatic resource protection, stormwater management programs, and ecological and human health risk assessment.

The watershed modeling services were accomplished cooperatively by King County staff and AQUA TERRA through an on-call services arrangement in terms of various work orders.

Sammamish-Washington Analysis and Modeling Program (SWAMP).

The purpose of this project was to evaluate the impact of urban and rural areas on the hydrology and water quality of the Sammamish and Lake Washington watersheds. This project involved an assessment of the existing King County modeling effort in this study area and linkage to the hydrodynamic models representing the downstream lakes (Sammamish and Washington). Strategies for water quantity and quality modeling were developed along the selection of the appropriate modeling tools. Water quantity and quality models were developed as needed and calibrated and validated prior to the investigation of different land use and operational scenarios in the watersheds.

Green-Duwamish Water Quality Assessment (GD-WQA).

The purpose of this project was to evaluate the impact of urban and rural areas on the hydrology and water quality of the Green and Duwamish watersheds. This project involved an assessment of the existing King County modeling effort in this study area and linkage to the hydrodynamic models representing the downstream estuary of Elliott Bay and Puget Sound. Strategies for water quantity and quality modeling were developed along the selection of the appropriate modeling tools. Water quantity and quality models were developed as needed and calibrated and validated prior to the investigation of different land use and operational scenarios in the watersheds.

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