Willwood Dam/Shoshone River Work Group Updates

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Wyoming Department of Environmental Quality

Willwood Dam/Shoshone River Work Group Updates



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

Buffalo Bill Dam Operations: Beginning in mid-October, the Bureau of Reclamation (BOR) adjusted flows out of Buffalo Bill to winter release levels of approximately 260 cfs at the gage near Cody. BOR intends to maintain this flow through the winter months. Winter releases are set based on criteria agreed to by the Wyoming State Engineer, Wyoming Water Development Office (WWDO), Wyoming Game and Fish Department (WGFD), and BOR. The criteria take into consideration reservoir inflow and storage conditions. The reservoir is approximately 68% full due to lower than normal precipitation this summer and fall.

Willwood Dam Fall Drawdown: In late October, Work Group 2 (Wyoming Department of Environmental Quality (WDEQ), WGFD, Willwood Irrigation District (WID), BOR, WWDO, Wyoming State Engineer’s Office, United States Geological Survey (USGS), Powell Clarks Fork Conservation District, and others) coordinated an approximately 16-day fall drawdown consistent with the 2019 Willwood Dam Operating Recommendations. Similar to 2019, the drawdown was closely monitored using the real-time USGS monitoring sites described below. The drawdown was also used as an opportunity to collect additional data to support the work of USGS and researchers from the University of Wyoming that will inform dam operations as well as other efforts of the Willwood Dam/Shoshone River Work Groups. The drawdown occurs on an annual basis and is necessary to prevent damage to the canal gates that can occur with freezing temperatures. The mid-October timeframe is intended to minimize potential impacts of sediment releases to the downstream fishery, particularly October 15th to November 15th, the fall spawning period for brown trout and mountain whitefish.

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 publishing daily average discharge at the upstream site. The data will be used to inform future dam operations by quantifying timing of sediment deposition and sediment releases from Willwood Dam. The data will also be used to identify sources of fine sediment to the dam that will assist Work Group 3’s 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 graduate student 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 2020. Fall 2020 fieldwork is focused on monitoring normal Willwood Dam fall drawdown conditions to quantify potential impacts on suitable brown trout and mountain whitefish spawning habitat. Crews are monitoring fine sediment deposition, hyporheic dissolved oxygen levels and water column suspended sediment concentrations at two sites below Willwood Dam. Generous field assistance from the WDEQ Sheridan office (Chad Rieger, Jason Martineau and Jeremy Zumberge), Powell Clarks Fork Conservation District and Willwood Dam/Shoshone River Work Group 3 (Carmen McIntyre), Willwood Irrigation District (Travis Moger, Troy Pimentel, July Krakel), WGFD (Jason Burkhardt), and Cody Trout Unlimited (David Sweet) has made this work possible. The project will continue until approximately June 2022.

Bathymetric Survey of Sediment Behind Willwood Dam: WDEQ has completed a preliminary analysis of bathymetric survey data of deposited sediment behind Willwood Dam that was collected in November 2017 and August 2019. The data shows that sediment movement behind the dam is very dynamic, mobilizing and depositing in different areas depending on factors that likely include climate patterns, pool elevation, and flow conditions. Work Group 2 is in process of securing resources to complete additional bathymetric surveys to help further (1) determine how Shoshone River flows and operations of Willwood Dam influence 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. The most recent survey was conducted in October 2020 upstream of Willwood Dam. As described in the June 2019 update, the most recent sampling conducted downstream of Willwood Dam occurred in March 2020. The estimates provided in that update were miscalculated. The corrected Spring 2020 estimates are as follows: the abundance of all trout (greater than six inches) was 334 trout/mile. Previous estimates showed abundance of all trout (greater than six inches) of 442 trout/mile in 2016, 654 trout/mile in 2017, and 763 trout/mile in 2018. The 2020 estimate of brown trout abundance (greater than six inches), the only species of trout not stocked in this section of river, was 149 trout/mile. Prior estimates of brown trout (greater than six inches) abundance were 146/mile in 2016, 125/mile in 2017, and 148 trout/mile in 2018. The lower estimates of all trout from 2020 are expected given that all prior sampling events were conducted in the fall. Trout abundance is likely lower in the spring 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 are typically well represented during the fall sampling; and (3) the size distribution of stocked trout showed very few large fish, suggesting 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.

Additional Efforts. Work Group 2 has two sub work group efforts occurring. The first effort is exploring approaches for reducing sediment at Willwood Dam with alternative sediment management and water delivery methods. The second effort is exploring ways to improve sediment mobilization during natural and induced higher flows.

Questions: Questions regarding Work Group 2 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).

The group remains focused on pursuing grant opportunities to continue water quality monitoring, project planning, and education/outreach activities. A Watershed Coordinator was hired in September by the Powell Clarks Fork Conservation District to assist the group in watershed planning and implementation. The District also secured funds through the Wyoming Department of Agriculture to install cameras on tributaries above Willwood Dam to aid the group in better understanding the relative sediment load contributions of the tributaries. The cameras will be especially helpful during precipitation events, when it is difficult to time mobilization of on-site samplers.

The Cody Conservation District recently secured funds through the National Association of Conservation Districts to hire a field technician who will work with producers and other partners to implement practices that reduce sediment inputs to the Shoshone River and conduct monitoring and outreach activities. The Wyoming Association of Conservation Districts and NRCS will also work with the Cody Conservation District in 2021 to refine planning efforts in the lower Sage Creek Watershed to become eligible for project implementation funds through the NRCS National Water Quality Initiative (NWQI).

Work Group 3 members from the Wyoming Game and Fish Department (WGFD) continue to lead sediment sampling efforts on tributaries to the Shoshone River and have completed 19 events as of Fall 2020. The WGFD also completed a Habitat Assessment Survey for three Work Group 3 priority watersheds (Sage Creek, Sulphur Creek, and Dry Creek/Homesteader Creek). In 2020, approximately 70 stream miles were surveyed to assess riparian and channel conditions and to identify project opportunities. Bureau of Land Management staff in the Cody Office have held several on-site meetings with WGFD, the local Trout Unlimited Chapter, NRCS, and Conservation District staff to discuss project opportunities in the Sulphur Creek drainage with the goal of beginning these projects in 2021.

The tour that was 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.

Questions: Questions regarding Work Group 3 efforts can be directed to Carmen McIntyre, Powell Clarks Fork Conservation District Watershed Coordinator, at 828-674-8541 or [email protected].