Developing Design Guidelines for Low Head Fish Friendly Diversion Dams
* Can we produce standard designs for low head diversion dams that couple irrigation diversion and fish passage without significant increase in cost?
* Can we incorporate the same construction methods with which irrigation districts are familiar?
* How can we reconfigure the typical sheetpile weir, rock sill or concrete block sill dam to provide fish passage and serve irrigation diversion needs?
Need and Benefit
Many low head (<5 feet) irrigation diversion dams are repaired or replaced or new diversions are constructed with the assistance of Federal programs each year. Reclamation and its partners in this proposal encounter these projects many times a year. Reclamation projects contain countless small diversion structures throughout the Western United States. The Natural Resources Conservation Service (NRCS) estimates that in Wyoming alone, they are involved in the replacement or construction of five to ten small diversion dams per year. Each year, the Wyoming Fish and Game is asked to comment on the fisheries impact of dozens of water diversion actions. As a result of no clear technical guidance or guidelines, most of these structures are constructed without effective fish passage. Until we identify science-based methods to combine gravity water diversion and fish passage in an economically viable way we will continue one hundred years of practice of building small diversions that inhibit the natural movement of fish and other aquatic organisms in our streams.
Research in recent years has shown that most native fish species found in western rivers do migrate to fulfill spawning or habitat needs. As examples, fishways designed for native species at Redlands and Grand Valley Diversion Dams on the Colorado River system record thousands of fish of multiple species passing each week (Burdick, FWS). Prior research conducted under the Science and Technology (S&T) Program has also demonstrated that relatively small drops when constructed as continuous sills can be major barriers to native species of western rivers (White and Mefford 2002, Bestgen and Mefford, 2003).
Prior S&T sponsored research has developed the baseline hydraulic and biological knowledge needed to design effective passage structures. The challenge now lies in incorporating this knowledge into guidance for design of low head diversion dams using simple construction methods familiar to water diverters.
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