Hydraulics, hydrology, and resulting fish passage at the Huntley Diversion Nature-like Bypass

Abstract

Dams and other instream structures have been constructed for hundreds of years in the United States for various purposes; these dams have the potential to 'disconnect' rivers and negatively impact fish upstream and downstream movement. Nature-like bypasses were created to facilitate movement around these structures and provide passage to a wide variety of morphologically different fish species. The Huntley Diversion Dam nature-like bypass was constructed in 2015 on the Yellowstone River, but its effectiveness has not yet been evaluated. This project aimed to evaluate its efficacy through monitoring and determining water stage, flow rates, channel roughness, and a detailed channel bathymetry. These data were then used in the creation of multiple two-dimensional hydraulic models encompassing the nature-like bypass channel and surrounding Yellowstone River area. Velocity results from these models were compared to species-specific swimming capabilities from literature for four Yellowstone River species. Additionally, hydraulics at the downstream bypass entrance were evaluated for disorienting hydraulic formations that might prevent fish from locating the bypass entrance. Velocity results indicate Sauger (Sander canadensis) may successfully ascend the bypass on all but five days of the modeled hydrograph and may face occasional difficulty in returning to their pre-spawning upstream habitat. Burbot (Lota lota), Channel Catfish (Ictalurus punctatus), and Smallmouth Bass (Micropterus dolomieu) are unlikely to successfully ascend the bypass for much of May, June, and July. This holds significant implications for Channel Catfish and Smallmouth Bass, both of which move upstream to spawn in the months of May and June. Hydraulics at the downstream end of the bypass indicate high attraction at high flows, but that lower flows are likely to create disorienting hydraulic characteristics at this bypass entrance and lead to low fish attraction.