Willwood Dam/Shoshone River Work Group Updates

Wyoming Department of Environmental Quality  | view as a webpage

Wyoming Department of Environmental Quality

Willwood Dam/Shoshone River Work Group Updates


Work Group 2 Meetings: Members of the public are encouraged to participate in Work Group 2 meetings, primarily conducted via conference call, advertised via this listserv.

Buffalo Bill and Willwood Dam Operations: The irrigation season is well underway along the Shoshone River. Water levels in Buffalo Bill Reservoir are typical for this time of year. As of late May, the snowpack was approximately 90% of normal. In response to hydrologic conditions, the Bureau of Reclamation will be adjusting releases from Buffalo Bill to facilitate filling the reservoir in June or July. At Willwood Dam, operations are typical for the irrigation season. The sluice gates are closed, the pool elevation is high and water is being diverted into the canal.  

Spring Sediment Mobilization: In late March and early April, Work Group 2 (Wyoming Department of Environmental Quality, Wyoming Game and Fish Department, Willwood Irrigation District, United States Bureau of Reclamation, Wyoming Water Development Office, Wyoming State Engineer’s Office, and others) coordinated an approximately 7-day spring sediment mobilization consistent with the 2019 Willwood Dam Operating Recommendations. The sediment mobilization may occur on an annual basis and is intended to help move some of the sediment that has been deposited behind Willwood Dam. The sediment mobilization is timed to minimize potential impacts to the downstream Shoshone River fishery by releasing sediment prior to higher spring flows to help prevent deposition of the sediment in sensitive habitats. The mobilization effort was closely monitored using the real-time United States Geological Survey (USGS) monitoring sites described below.

United States Geological Survey (USGS) Monitoring: Work Group 2 continues to partner with USGS to provide water level, turbidity, and suspended sediment concentration data upstream (06283995) and discharge, turbidity, and suspended sediment concentration data downstream (06284010) of Willwood Dam on the Shoshone River. The data is logged in real-time, transmitted on an hourly schedule, and available for public access on the USGS website using the links above. USGS is working toward providing real-time discharge measurements at the upstream site and plans to collect additional suspended-sediment samples at the upstream site to improve real-time suspended sediment estimates. The data will be used to inform future dam operations by determining the quantity and timing of sediment deposition behind Willwood Dam and determine the quantity and timing of sediment releases from Willwood Dam; and help identify sources of sediment to Willwood Dam to inform Work Group 3 efforts to reduce nonpoint sources of sediment to the Shoshone River.

University of Wyoming Water Research Program Study: Work Group 2 continues to work with University of Wyoming fisheries biologists and a Master’s candidate on a Water Research Program project that will (1) synthesize the current state of knowledge of sediment effects on fisheries; and (2) evaluate metrics and approaches for identifying sediment levels protective of fisheries. Data collection at sites on the Shoshone River downstream of Willwood Dam that began in August 2019 will continue through 2021. Intensive monitoring of sensitive spawning habitats occurred during the fall drawdown in 2019 and may occur during the fall drawdown in 2020. The project will continue until approximately June 2022.

Bathymetric Survey of Sediment Behind Willwood Dam: WDEQ is in the process of analyzing bathymetric survey data of deposited sediment behind Willwood Dam that were completed in November 2017 and August 2019. The data will be used to (1) determine how flows and operations of Willwood Dam have changed the quantity and location of deposited sediment; and (2) help determine how to best manage deposited sediment while also protecting the downstream fishery.

Wyoming Game and Fish: WGFD fish management crews continue to collect trout abundance and condition data on the Shoshone River, with the most recent sampling conducted this spring. Sampling typically occurs during the fall, however, sampling was not possible in the fall of 2019 due to unsuitable water conditions. The spring 2020 estimate showed an abundance of all trout greater than six inches of 172 trout/mile. Previous estimates showed an abundance of all trout greater than six inches of 442 trout/mile in 2016, 585 trout/mile in 2017, and 763 trout/mile in 2018. The spring 2020 estimate of the abundance of brown trout greater than six inches, the only species of trout not stocked in this section of river, was 84/mile. Prior estimates of the abundance of brown trout greater than six inches were 146/mile in 2016, 125/mile in 2017, and 148 trout/mile in 2018. The spring 2020 results are not directly comparable to the previous fall estimates and are expected to be lower because (1) winter conditions are known to limit many trout populations; (2) rainbow and cutthroat trout stocked in the spring and early summer in this section of the Shoshone River typically comprise a large portion of the fish collected in the fall; and (3) the size distribution of stocked trout suggest that few stocked trout persist for more than one year. The WGFD will continue to monitor this population and work with the Willwood Working Groups to find ways to maintain the best possible fishery in this section of the Shoshone River.

Department of Environmental Quality (DEQ) Shoshone River Water Quality Monitoring: The DEQ’s Monitoring Program completed collection of monthly water quality samples at nine sites on the Shoshone River from Cody downstream to Lovell in 2019. Biological sampling (macroinvertebrates and periphyton) at all nine sites was conducted in September 2019 and will supplement samples collected at the same sites in August 2018. Chemical and biological sampling results from 2018 and 2019 are currently being analyzed.

Questions: Questions regarding these efforts can be directed to David Waterstreet, Watershed Protection Program Manager, Water Quality Division, Wyoming Department of Environmental Quality, at [email protected] or 307-777-6709.


Work Group 3 continues to meet regularly and is making steady progress toward implementing the first key steps outlined in the completed watershed plan (available at https://arcg.is/0PmPvS and https://arcg.is/1ymq19). Currently, the group is focused on mobilizing resources to pursue grant opportunities, continue water quality monitoring efforts, and conduct outreach activities. The group applied for and secured a WaterSmart grant through the Bureau of Reclamation; these grant funds will be used to hire a watershed coordinator who will help with stakeholder outreach, watershed monitoring, and project planning. The group is evaluating numerous other financial assistance opportunities and has several applications submitted or in-process. Work group members from the Wyoming Game and Fish Department continue to lead sediment sampling on tributaries to the Shoshone River, and the work group has begun discussing data analysis opportunities with USGS. The tour tentatively planned for summer 2020 has been postponed until summer 2021; please stay tuned for more information about future tours. Work Group 3 participation remains open to all interested parties.