Fish Passage Mitigation Of Impacts From Hydroelectric Power Projects In The United States

Obstruction of fish movements by dams continues to be the major environmental issue facing the hydropower industry in the US. Dams block upstream migrations, which can cut off adult fish form their historical spawning grounds and severely curtail reproduction. Conversely, downstream-migrating fish may be entrained into the turbine intake flow and suffer turbine-passage injury or mortality. Hydroelectric projects can interfere with the migrations of a wide variety of fish. Maintenance, restoration or enhancement of populations of these species may require the construction of facilities to allow for upstream and downstream fish passage. The Federal Energy Regulatory Commission (FERC), by law, must give fish and wildlife resources equal consideration with power production in its licensing decisions, must be satisfied that a project is consistent with comprehensive plans for a waterway (including fisheries management plans), and must consider all federal and state resource agency terms and conditions for the protection of fish and wildlife. As a consequence, FERC often requires fish passage mitigation measures as a condition of the hydropower license when such measures are deemed necessary for the protection of fish. Much of the recent research and development efforts of the US Department of Energy's Hydropower Program have focused on the mitigation of impacts to upstream and downstream fish passage. This paper descries three components of that effort: (1) a survey of environmental mitigation measures at hydropower sites across the country; (2) a critical review of the effectiveness of fish passage mitigation measures at 16 case study sites; and (3) ongoing efforts to develop new turbine designs that minimize turbine-passage mortality.

The focus of this report is technologies for fish passage around hydropower generation facilities and protection against entrainment and turbine mortality. Emphasis is given to Federal Energy Regulatory Commission (FERC)-licensed hydropower projects where fish protection is a subject of controversy and congressional interest due to the Federal Power Act (FPA) and the Electric Consumers Protection Act (ECPA). Thus institutional issues related to FERC-relicensing are also discussed. (Major points of controversy are high-lighted in box 1.1).

The US Department of Energy's Hydropower Program is engaged in a multi-year study of the costs and benefits of environmental mitigation measures at nonfederal hydroelectric power plants. An initial report (Volume 1) reviewed and surveyed the status of mitigation methods for fish passage, instream flows, and water quality; this paper focuses on the fish passage/protection aspects of the study. Fish ladders were found to be the most common means of passing fish upstream; elevators/lifts were less common, but their use appears to be increasing. A variety of mitigative measures is employed to prevent fish from being drawn into turbine intakes, including spill flows, narrow-mesh intake screens, angled bar racks, and lightor sound-based guidance measures. Performance monitoring and detailed, quantifiable performance criteria were frequently lacking at non-federal hydroelectric projects. Volume 2 considers the benefits and costs of fish passage and protection measures, as illustrated by case studies for which performance monitoring has been conducted. The report estimates the effectiveness of particular measures, the consequent impacts on the fish populations that are being maintained or restored, and the resulting use and non-use values of the maintained or restored fish populations.

Research into the environmental effects of hydroelectric power production in the United States has focused increasingly on resident and migratory fish populations. Hydropower dams and reservoirs can block fish movements in both upstream and downstream directions. These movements are essential for important stocks of anadromous and catadromous fish. In addition, some strictly freshwater fish may move long distances within a river during their life cycle. A dam can pose an impassable barrier for fish trying to move upstream unless mitigation measures in the form of ladders or lifts are provided. Fish moving downstream to the sea may become disoriented when they encounter static water within a reservoir. Both resident and migratory fish may be injured or killed by passing through the turbine or over the spillway. In the United States, a variety of organizations conduct applied research and development of measures to (1) enhance fish passage, (2) reduce the numbers of fish that are drawn into the turbine intakes, and (3) reduce the injury and mortality rates of fish that pass through the turbines. Examples of these efforts from a variety of river systems and hydroelectric power plants are described.