A primary issue of concern of regulatory and resource agencies is how the operation of hydrokinetic turbines will affect local and migratory fish populations. In particular, two major concerns are the potential for fish to be killed or injured if they pass through one or more turbines and the potential for fish movements and migrations to be disrupted or blocked if fish are reluctant or unwilling to move past operating turbines. Fish that pass through hydrokinetic turbines may be injured or killed due to blade strike or damaging hydraulic shear and/or pressure conditions. This collection of three reports describes desktop and laboratory flume studies that provide information to support assessment of the potential for injury and mortality of fish that encounter hydrokinetic turbines of various designs installed in tidal and river environments. Behavioral responses to turbine exposure also are investigated to support assessment of the potential for disruptions to upstream and downstream movements of fish.
Accurate and precise determination of the probability of blade strike and injury, and of the behavior of fish as they encounter hydrokinetic turbines, was the primary goal of the studies. This goal is achieved by: (1) conducting an assessment of potential injury mechanisms using available data from studies with conventional hydro turbines; (2) developing theoretical models for predicting blade strike probabilities and mortality rates; and (3) performing flume testing with three turbine designs and several fish species and size groups in two laboratory flumes to estimate survival rates and document fish behavior. The strike probability and mortality models are verified using data collected during flume testing. These desktop analyses include an assessment of existing biocriteria for the safe passage of fish through conventional hydro turbines with respect to relevance and application to hydrokinetic devices, and development of theoretical models for predicting blade strike and mortality probabilities. Flume studies were conducted with three hydrokinetic turbine designs and several fish species/sizes to estimate turbine passage survival and injury rates and to determine behavior of fish as they approach and encounter operating turbines. Flume testing was conducted at Alden and CAFRL.
The project provides valuable data and information on behavior and injury and survival rates of fish passing hydrokinetic turbines. The behavioral data demonstrate that fish approaching turbines actively avoid passing through the blade sweep area. Estimates of survival and injury allow potential losses of fish to be determined for single or multiple unit installations. The information from these studies facilitates determination of potential impacts to fish populations and may diminish the need for expensive field studies, which often provide only marginal or incomplete data.
The project yielded three reports which this document comprises. The three constituent documents are:
- Fish Passage Through Turbines: Application of Conventional Hydropower Data to Hydrokinetic Technologies (EPRI Report ID 1024638)
- Evaluation of Fish Injury and Mortality Associated with Hydrokinetic Turbines (EPRI Report ID 1024569)
- Survival and Behavior of Juvenile Atlantic Salmon and Adult American Shad on Exposure to a Hydrokinetic Turbine (EPRI Report ID 1026904)
Fish Passage Through Turbines: Application of Conventional Hydropower Data to Hydrokinetic Technologies This report reviews information on impacts of conventional hydropower turbines that can be used to evaluate potential impacts of hydrokinetic turbines on fish. The report discusses design and operational differences between conventional and hydrokinetic turbines as well as differences in the magnitude or potential for fish injury and mortality.
Fish passing through the blade sweep of a hydrokinetic turbine experience a much less harsh physical environment than do fish entrained through conventional hydro turbines. The design and operation of conventional turbines results in high flow velocities, abrupt changes in flow direction, relatively high runner rotational and blade speeds, rapid and significant changes in pressure, and the need for various structures throughout the turbine passageway that can be impacted by fish (e.g., walls, stay vanes, wicket gates, flow straighteners). Most, if not all, of these conditions do not occur or are not significant factors for hydrokinetic turbines. Furthermore, compared to conventional hydro turbines, hydrokinetic turbines typically produce relatively minor changes in shear, turbulence, and pressure levels from ambient conditions in the surrounding environment. Injuries and mortality from mechanical injuries will be less as well, mainly due to low rotational speeds and strike velocities, and an absence of structures that can lead to grinding or abrasion injuries. While information pertaining to conventional hydro turbines is useful for assessing the potential for adverse effects of passage through the swept area of hydrokinetic turbines, additional information is needed to rigorously assess the nature and magnitude of effects on individuals and populations, and to refine criteria for design of more fish-friendly hydrokinetic turbines.
Evaluation of Fish Injury and Mortality Associated with Hydrokinetic Turbines Potential for fish to be injured or killed if they encounter hydrokinetic turbines is an issue of significant interest to resource and regulatory agencies. To address this issue, flume studies were conducted that exposed fish to two hydrokinetic turbine designs to determine injury and survival rates and to assess behavioral reactions and avoidance. Also, a theoretical model developed for predicting strike probability and mortality of fish passing through conventional hydro turbines was adapted for use with hydrokinetic turbines and applied to the two designs evaluated during flume studies. The flume tests were conducted with the Lucid spherical turbine (LST), a Darrieus-type (cross flow) turbine, and the Welka UPG, an axial flow propeller turbine. Survival and injury for selected species and size groups were estimated for each turbine operating at two approach velocities by releasing treatment fish directly upstream and control fish downstream of the operating units. Behavioral observations were recorded with underwater video cameras during survival tests and during separate trials where fish were released farther upstream to allow them greater opportunity to avoid passage through the blade sweep of each turbine. Survival rates for rainbow trout tested with the LST were greater than 98% for both size groups and approach velocities evaluated.
Turbine passage survival rates for rainbow trout and largemouth bass tested with the Welka UPG were greater than 99% for both size groups and velocities evaluated. Injury rates of turbine-exposed fish were low for tests with both turbines and generally comparable to control fish. When adjusted for control data, descaling rates were also low (0.0 to 4.5%). Video observations of the LST demonstrated active avoidance of turbine passage by a large proportion fish despite being released about 25 cm upstream of the turbine blade sweep. Video observations from behavior trials indicated few if any fish pass through the turbines when released farther upstream. The theoretical predictions for the LST indicated that strike mortality would begin to occur at an ambient current velocity of about 1.7 m/s for fish with lengths greater than the thickness of the leading edge of the blades. As current velocities increase above 1.7 m/s, survival was predicted to decrease for fish passing through the LST, but generally remained high (greater than 90%) for fish less than 200 mm in length.
Strike mortality was not predicted to occur during passage through a Welka UPG turbine at ambient current velocities less than about 2.5 m/s. This research effort has resulted in a better understanding of the interactions between fish and hydrokinetic turbines for two general design types (vertical cross-flow and ducted axial flow). However, because the results generally are applicable to the presence of a single turbine, more analysis is needed to assess the potential for multiple units to lead to greater mortality rates or impacts on fish movements and migrations. Additionally, future research should focus on expanding the existing data by developing better estimates of encounter and avoidance probabilities.
Survival and Behavior of Juvenile Atlantic Salmon and Adult American Shad on Exposure to a Hydrokinetic Turbine This report describes a series of experiments designed to measure the effect of exposure to a full-scale, vertical axis hydrokinetic turbine on downstream migrating juvenile Atlantic salmon (N=173) and upstream migrating adult American shad (N=208). Controlled studies were performed in a large-scale, open-channel flume, and all individuals approached the turbine under volitional control. No injuries were observed, and there was no measurable increase in mortality associated with turbine passage. Exposure to the turbine elicited behavioral responses from both species, however, with salmon passing primarily over the downrunning blades. Shad movement was impeded in the presence of the device, as indicated by fewer attempts of shorter duration and reduced distance of ascent up the flume. More work should be performed in both laboratory and field conditions to determine the extent to which these effects are likely to influence fish in riverine environments.