Fish Passage at River Diversion Juncture: A Science-Based Approach
The proposed research is to develop a science-based approach for design and evaluation of alternatives that may enhance fish entrainment or reduce fish passage through a diversion channel at a river juncture. Downstream migrating juvenile salmon will be the target. It will answer the following research questions: (1) Can fish passage through a diversion channel at a river juncture be predicted using a science-based, numerical modeling tool? (2) Can the diversion channel may be manipulated to increase the fish entrainment? (3) Can the effect of a physical boom, as a fish barrier, on fish passage through the diversion channel be predicted? (4) What are the key hydrodynamic features that fish will respond to?
Need and Benefit
Reclamation has a mission of delivering water in the western U.S. states. The water delivery, however, has been impacted by the need to meet regulations for fish passage at many Reclamation facilities. Annually, a large amount of Reclamation resources have been devoted to addressing the issue of fish passage. Despite the significant amount of effort devoted to the topic and increased knowledge of fish passage, the current practice of fish passage designs has mostly been exploratory, empirical, and ad hoc. There is an urgent need for the development of a science-based approach, which has been championed by scientists in the fish passage community for many years. This proposed research represents such an effort by adopting numerical models as a science-based approach which has been emerged as a prominent candidate. The study will be based on the current knowledge of fish responses to flow hydrodynamics and the use and improvements of a modeling tool named CFD-ELAM.
The CFD-ELAM approach for fish passage is an emerging field. Early work was mostly on juvenile salmonid migration through hydropower dams reported by, e.g., Goodwin (2004), Goodwin et al. (2006), and Smith et al. (2010).The success of the modeling tool for the downstream migration fish passage at reservoirs has not been transferable to fish passage in the rivers or for upstream fish migration. Obstacles are two-folds: inability of the existing models in predicting the complex flow hydrodynamics experienced by fish in rivers, and (b) lack of understanding of fish responses to flow features in the riverine environment. Fish behavior changes to flow features near local structures are well known in a riverine environment. Recent relevant studies include McNamara et al. (2013), Goodwin et al. (2014), Dabiri (2017), and Oteiza et al. (2017), among others. These studies showed that the time may have been ripe to develop a new CFD-ELAM approach for fish passage in rivers. Some effort reported recently includes the studies by Bever and MacWilliams (2015), Ramon et al. (2018), and Goodwin, Lai, Smith, et al. (2018).
This research proposes to develop an improved CFD-ELAM approach, specifically targeting for downstream migrating, juvenile salmonid, for fish entrainment or barrier at a river diversion juncture. There are a wide range of fish passage projects at Reclamation that occur at such junctures and need a tool such as CFD-ELAM. Sample projects include the Yolo Bypass EIS/EIR study at the Fremont Weir (Sac River), fish barrier projects at the Georgiana-Slough (Sac River) and Head of the Old River (San Joaquin), the mouth of Mill Creek with the Sac River, and various project at the UP Region. The proposed research at river junctures establishes a baseline to verify the CFD-ELAM approach as a science-based approach and paves a way towards fish passage in other riverine environments.
The research builds on the previous works of the CFD-ELAM approach developed for downstream salmonid migrating at reservoirs, provides a new science-based tool for fish passage projects at river junctures, and develops a guideline for diversion channel design for fish entrainment or fish barrier.
The proposed science-based, modeling approach towards the fish passage design and evaluation will benefits all Reclamation offices since most are involved in fish passage projects. Significant benefits of the proposed approach include its generality in theory, cost-effectiveness in design and evaluation, defendability to stakeholders and permitting agencies, and adaptivity to a specific site if necessary. The CFD-ELAM approach can be carried out on a desktop computers, and is faster and cheaper than most current empirical or lab and field-based methods. The time and cost saving would be multiple times in comparison with the current practices, if not order of magnitude reduction in design and evaluation study.
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