Increasing Reliability of Power Generation and Irrigation Water Delivery at Bighorn Reservoir through Investigation of Current Effects on Native Fish and Development of Management Recommendations to Reduce those Effects.
Bighorn Reservoir, in Montana and Wyoming, is a keystone feature of the Bighorn Basin operated for project purposes of irrigation and hydropower (and reservoir elevations fluctuate accordingly). The upper portion of the reservoir is suspected to be an important macrohabitat for native fish, some of which are potential candidates for listing under the Endangered Species Act. This proposal seeks to address the following questions:
* What are the movement patterns and habitat use requirements of native fish in the upper portion of the reservoir?
* Do current operations affect these fish?
* Are there management recommendations that could reduce any adverse effects to these fish while still maintaining or increasing reliability of power generation and irrigation delivery?
Need and Benefit
Bighorn Reservoir elevations are known to fluctuate both seasonally and annually in response to irrigation and hydropower demands associated with the Pick-Sloan Missouri Basin Program.
The reservoir is confined to canyon for most of its length, except for the joint-use portion of the reservoir in the Bighorn Basin. This portion is considered an important macrohabitat for native fish and is most susceptible to the effects of reservoir drawdown. Temporal and spatial patterns, as well as habitat preferences of these fish in relation to operational fluctuations, have not been documented.
Several native fishes in Bighorn Reservoir are considered Species of Special Concern (SSC). This designation is considered a preliminary indication that the species may become a candidate for listing under the Endangered Species Act (ESA) if their decline is not reversed. Sauger are designated a SSC in both Montana and Wyoming and are known to use the upper end of the reservoir as wintering and nursery habitat. Burbot are present in the reservoir and are a candidate for listing under the ESA in certain areas of Montana. Yellowstone cutthroat trout are present in some tributaries of the reservoir, and have been petitioned for listing under the ESA; these trout are also designated as SSC by Montana Fish, Wildlife, and Parks, and the Crow Tribe (the Tribe is an end water user for irrigation from Bighorn Reservoir.) This proposal would study the effects of current project operations on these and other native species and explore recommendations to reduce these effects, if any.
Native fish are of special concern to Reclamation operations on Bighorn Reservoir/Yellowtail Dam because they have the ability to directly impact power production and irrigation releases in the event that a species or population of fish within the reservoir is listed for protection under the ESA. Yellowtail Dam's annual power generation over a 10 year period has averaged 974, 400 megawatt-hours (MWhr). This the economic value of this energy is estimated at $35.00 per MWhr, (approximately thirty-four million dollars annually). If a species or population is listed, a stabilized flow regime through Bighorn Reservoir could be mandated as part of a species or population recovery plan. Stabilized flows could seriously impact peaking power discharges. For example, a 10 percent decrease in annual MWhr production due to a (hypothetically) mandated stabilized flow regime would cost $3, 400, 000 in lost power production revenue.
Determining spatial and temporal patterns, as well as habitat preferences of these species, will facilitate continued water and power delivery to Reclamation's stakeholders by anticipating and addressing environmental concerns before they reached a point where deliveries were impacted. Further, Reclamation operations would have the ability to address the specific ecosystem needs of the reservoir's native fish while meeting stakeholder demands.
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