26934 REL 4

2003-038-00 EXP EVAL RESTOR OF SNAKE R CHINOOK

10/1/2006

1/31/2007

162. Analyze/Interpret Data

Work Element Usage Report

D: 162 - Analyze lower Snake River study sites

Apply hydrodynamic model(s) to the study sites to estimate two-dimensional hydraulic characteristics under different flow scenarios. Estimating hydraulic characteristics through the use of a hydrodynamic model is necessary because the study sites are currently impounded. Scenarios would include incremental drawdown of forebay elevations between spillway crest and normal operating pool, including an elevation that would allow the travel of shallow draft barges. The modeling evaluation would also include an analysis of flow scenarios by water-year type (extremely wet, wet, normal, dry, extremely dry) to account for natural variation in hydrologic regime. Water-year types would be determined based on runoff volume at The Dalles Dam by July 1.

To simulate the spatial distribution of water depth and velocity under different project operating conditions, it is proposed that a two-dimensional depth-averaged hydrodynamic and water quality model be applied to the Ice Harbor and Lower Granite tailraces. We propose to use the existing two-dimensional MASS2 (Richmond et al., 2000) model to simulate the majority of the river section (i.e. from below Lower Granite Dam to the river's confluence with the Columbia). The MASS2 model has already been applied to these river reaches. In this project we will update the bathymetry, computational grid, and perform additional validation simulations using velocity and stage data collected for this project.

MASS2 is a two-dimensional depth-averaged hydrodynamic and water quality model. The model simulates time-varying distributions of the depth-averaged velocities, water temperature, and total dissolved gas. The model is a finite-volume code that is formulated using the general principles described by Patankar (1980), and uses a structured multi-block scheme on a curvilinear grid system. Heat exchange at the air-water surface is computed using a physical based approach based upon commonly observed meteorological conditions (Edinger et al., 1974). Dissolved gas concentrations are transported using the two-dimensional form of the advection-diffusion equation, with appropriate source/sink terms for gas exchange. The model also includes a wetting-drying algorithm to simulate conditions where the wetted channel area is initially unknown or varies in time because the upstream inflow and/or downstream stage are unsteady. The wetting-drying capability is currently being used in unsteady simulations of hydraulic conditions in the Hanford Reach of the Columbia River.

MASS2 has previously been calibrated and verified to portions of the Columbia and Snake River systems, including the lower Snake River from LGR to the Columbia River confluence (Richmond et al., 1999a). The model was then used to simulate gas concentrations under various flow release alternatives (Richmond et al., 2000). MASS2 has also been applied to simulate the sediment erosion and deposition in the river under impounded (current) and unimpounded (four lower Snake dams removed) conditions (Richmond et al., 1999b).

This element includes: applying hydrodynamic models(s) to the study sites to estimate two-dimensional hydraulic characteristics under different flow scenarios; summarizing the physical characteristics at each study site for each flow scenario and water-year type.

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0.00%

10/01/2006

09/30/2007

Other

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Recurring