Evaluation of Wanapum Dam Bypass Configurations for Outmigrating Juvenile Salmon Using Virtual Fish: Numerical Fish Surrogate (NFS) Analysis

TitleEvaluation of Wanapum Dam Bypass Configurations for Outmigrating Juvenile Salmon Using Virtual Fish: Numerical Fish Surrogate (NFS) Analysis
Publication TypeMiscellaneous
Year of Publication2005
AuthorsGoodwin, RA, Nestler, JM, Anderson, JJ, Kim, J, Toney, T
AbstractAs part of the Federal Energy Regulatory Commission (FERC) relicensing process, Public Utility District No. 2 of Grant County (the District) wishes to improve performance of fish bypass at Wanapum Dam. The Numerical Fish Surrogate (NFS) is a Eulerian-Lagrangian-agent model (ELAM) developed for analyzing, decoding, and forecasting the movement and passage behavior response of outmigrating juvenile salmon (migrants) in complex 3-D hydrodynamic fields near fish bypass systems in hydropower dam forebays. The NFS (and ELAMs, in general) uses a mechanistic "plug-and-play" behavior algorithm embodying a biological hypothesis of how an individual responds to biotic and/or abiotic stimuli. The University of Iowa IIHR - Hydroscience and Engineering developed a computational fluid dynamics (CFD) model to describe the 3-D steady-state hydrodynamic fields associated with 12 different structural and operational fish bypass system configurations (cases) at Wanapum Dam. In Phase 1 of the study, forecast (virtual fish) and observed (radio-tagged fish) passage proportions were compared for five different cases from years 1997, 2001, and 2002. Comparison of forecast and observed passage for four out of the five cases were done blindly (i.e., independently reviewed and evaluated) and within the expected limits of about 5 to 10 percent for the bypass systems and considerably better than forecasts of passage from passive particles (i.e., behavior rules turned off). This indicates migrant movement behavior in the flow field is likely an integral part of bypass success. In Phase 2 of the study, the NFS was used to forecast the passage response of migrants to seven different structural and operational design alternatives under consideration for Wanapum Dam prior to construction and installation. Results indicate the NFS is a viable technology for use at Wanapum Dam to assess different fish bypass design alternatives. NFS performance is limited by (a) the robustness of the underlying mechanistic biological hypothesis, (b) accuracy and resolution of the CFD modeled hydrodynamics, and (c) accuracy and robustness of the observed (radio-tagged fish) passage proportions for describing the passage response of a target species or population. Concurrence between forecast and observed passage proportions supports the Strain-Velocity-Pressure (SVP) Hypothesis as an approximation of the strategy used by migrants to hydraulically navigate through complex flow fields. The NFS may be used to reduce uncertainty and, therefore, the cost and impact on migrants, in the process of designing and operating bypasses. NFS accuracy is expected to improve with additional observed data and model calibration.