Tarang Khangaonkar

Modeling Hydrothermal Response of a Reservoir to Modifications at a High-Head Dam

Abstract Pronounced stratification and peaking operation, typical of reservoirs impounded by high-head dams, result in complex current patterns. These cause disorientation in downstream migrating salmon and interfere with downstream passage. Structural and operational modifications such as installations of curtains, surface withdrawal, draw down, and selective withdrawal are often considered to alter the stratification and modify the currents to enhance the movement of fish toward the forebay where they may be collected effectively. Effectiveness of design modification in deep reservoirs is highly dependent on site-specific hydraulic and meteorological conditions, and numerical models are the tools of choice in design and selection of the optimum alternative. Although most hydropower reservoirs exhibit a vertical-longitudinal 2-D current structure, 3-D flow patterns are prevalent in reservoirs with multiple branches, and they occur near the power intakes as well. Simulation of these currents requires a 3-D hydrodynamic resolution. However, high-resolution hydrodynamic models, coupled with heat balance and water quality, have extensive computational demands and are unsuitable for iterative application or long-duration runs. An efficient strategy was developed where a vertical-longitudinal 2D heat balance model (BETTER) was used to generate rapid, year-long simulations of temperature and stratification in the reservoir. The predicted temperature distribution provided initial conditions for focused application of the 3-D hydrodynamic model (EFDC) to predict current patterns during the fish migration seasons only. A Lagrangian particle tracking technique was used to rank the effectiveness of each alternative in terms of guiding fish to the forebay, thereby improving potential for success. Selective surface withdrawal was found to be the most effective way to improve currents for enhancement of fish passage and help manage in-lake and discharge temperatures at Round Butte Dam in Lake Billy Chinook, Oregon.

Application of a Hydrodynamic and Sediment Transport Model for Restoration Feasibility Assessment at Cottonwood Island, Washington

A 3D hydrodynamic and sediment transport modeling analysis was conducted to evaluate the feasibility of restoring natural fish habitat in the Skagit River estuary, located in the northern Puget Sound, Washington. The Cottonwood Island restoration site is located where the north and the south forks of the Skagit River bifurcate approximately 10 river miles upstream from the mouth of the river. The study site is a riverine tidal and floodplain forest zone which is influenced by tide but not mixed with marine water, and is periodically inundated by flooding events. Fish habitat and migration pathway in the area was lost due to sedimentation in the channel around Cottonwood Island. Restoration actions were proposed to reconnect the channel sloughs to the main stem of the river to restore fish habitat. The analysis focused on estimating the potential for success associated with the proposed three restoration alternatives including dike setback and channel modification. In this study, the unstructured Finite Volume Coastal Ocean Model (FVCOM) was used to evaluate the effects of proposed alternatives on hydrodynamic response and potential channel re-sedimentation. The numerical model was calibrated with ADCP and CTD measurements. The calibrated hydrodynamic model was used to drive the sediment transport model to calculate sediment erosion and deposition patterns under different flow conditions. The model was applied to baseline and alternative conditions for 5 different flood hydrographs (1-yr, 2-yr, 5-yr, 10-yr, 25-yr). Model results for the alternatives were compared with baseline condition to assess the relative effects and potential re-sedimentation.

Development and evaluation of a coupled hydrodynamic (FVCOM) and water quality model (CE-QUAL-ICM)

Recent and frequent fish-kills in waters otherwise known for their pristine high quality, created increased awareness and urgent concern regarding potential for degradation of water quality in Puget Sound through coastal eutrophication caused by increased nutrient loading. Following a detailed review of leading models and tools available in public domain, FVCOM and CE-QUAL-ICM models were selected to conduct hydrodynamic and water quality simulations for the fjordal waters of Puget Sound.

Using FRAMES to Manage Environmental and Water Resources

The Framework for Risk Analysis in Multimedia Environmental Systems FRAMES) is decision-support middleware that provides users the ability to design software solutions for complex problems. It is a software platform that provides seamless and transparent communication between modeling components by using a multi-thematic approach to provide a flexible and holistic understanding of how environmental factors potentially affect humans and the environment. It incorporates disparate components (e.g., models, databases, and other frameworks) that integrate across scientific disciplines, allowing for tailored solutions to specific activities. This paper discusses one example application of FRAMES, where several commercialoff-the-shelf (COTS) software products are seamlessly linked into a planning and decision-support tool that helps manage water-based emergency situations and sustainable response. Multiple COTS models, including three surface water models, and a number of databases are linked through FRAMES to assess the impact of three asymmetric and simultaneous events, two of which impact water resources. The asymmetric events include 1) an unconventional radioactive release into a large potable water body, 2) a conventional contaminant (oil) release into navigable waters, and 3) an instantaneous atmospheric radioactive release.

Modeling of Tidal Circulation and Pollutant Transport in Port Angeles Harbor and Strait of Juan de Fuca

Strait of Juan de Fuca is a tidal energy pathway, which connects the Northeast Pacific Ocean continental shelf to the Strait of Georgia and Puget Sound. Complex circulation patterns, such as strong tidal fronts and eddies are observed in this high tidal energy regime, especially near the complex coastlines. These tidal fronts and eddies have significant effect on the dilution, trapping and transport of effluent discharges. A three-dimensional hydrodynamic model was developed to simulate the tidal circulation and pollutant transport in the eastern region of Strait of Juan de Fuca using the Environmental Fluid Dynamic Code (EFDC). In the present study, the model was driven by major semi-diurnal and diurnal tidal constituents, as well as surface winds. The model domain consists of multiple open boundaries, which connect to the ocean water and a number of estuarine systems. Historical water surface elevation, ADCP data, and surface drogue trajectories were used to calibrate the model over a period covering the spring and neap tidal cycle. To study the tidal eddy and transport processes near the Port Angeles Harbor located on the southeast shores of Strait of Juan de Fuca, a localized high-resolution boundary-fitted model grid was generated. The model successfully reproduced the tidal dynamics in the study area and good agreements between model results and observed data were obtained. The calibrated model was applied to simulate the transport and deposition of total suspended solids (TSS) discharged within the Port Angeles Harbor using weighted average of multiple particle sizes corresponding to typical secondary pulp mill effluent. The TSS deposition rates corresponding to different outfall characteristics were calculated and sediment impact zones in the Port Angeles Harbor area were analyzed.

Temperature Stratification and Water Quality Modeling for Lake Simtustus, Oregon

Lake Simtustus, impounded by the Pelton Dam, is the second of three reservoirs that are a part of Portland General Electrics (PGEs) Pelton/Round Butte Hydroelectric Project, located on the Deschutes River in central Oregon. Lake Simtustus is a narrow, deep lake with a flow field that is strongly affected by daily peaking inflows, outflows, and thermal stratification. This paper describes the development of a water quality model of Lake Simtustus to support PGEs proposed modifications to project operations for enhancement of fish passage. A dynamic, laterally averaged, vertical, 2-D water quality model for Lake Simtustus was developed using the CE-QUAL-W2 model to predict water quality under existing project conditions and to evaluate the impacts on water quality that would result from the proposed modifications to project operations. Model calibration was complicated by the fact that Lake Simtustus exhibits sharp density destratiflcation in the fall and has two pronounced algal growth seasons (spring and fall blooms) that are dominated by a different algal species. The water quality in the hypolimnion is dominated by the cooler inflows while the water quality in the epilimnion is dominated by meteorological forcing and in-lake t Senior Water Resources Engineer, Foster Wheeler Environmental Corporation, 12 I00 NE 195 th Street, Suite 200, Bothell, WA 98011 2 Senior Consulting Engineer, Foster Wheeler Environmental Corporation, 12100 NE 195 ~ Street, Suite 200, Bothell, WA 98011 3 Water Quality Engineer, King County Wastewater Treatment Division, Department of, Natural Resources, 201 South Jackson Street MS KSC-NR-0503, Seattle, WA 98104 4 Project Manager, Portland General Electric, 121 SW Salmon Street, Portland, OR 97204