Willwood Dam and Shoshone River February 2018 Update

Wyoming Department of Environmental Quality  | view as a webpage

Wyoming Department of Environmental Quality

Willwood Dam and Shoshone River Update

Presentations from November 28, 2017 Public Meeting: Thank you to everyone who attended the November 28, 2017 public meeting in Cody. Updates were provided on the: Wyoming Department of Environmental Quality’s (WDEQ) water quality monitoring efforts; Wyoming Game and Fish Department’s fish sampling results; draft operating recommendations for Willwood Dam; and data collection efforts upstream and downstream of the dam by the United States Geological Survey (USGS). We have posted the presentations from that meeting in the “Program Resources” at the bottom of the Willwood Dam and Shoshone River page.

Operating Recommendations: The public comment period for the Willwood Dam Operating Recommendations closed on December 22, 2017. WDEQ is currently reviewing the comments received and will work with cooperating agencies to develop responses. WDEQ will then make any necessary changes to the recommendations. WDEQ plans to make additional updates to the recommendations as new data and information become available.

Winter and Springs Flows in the Shoshone River: Following unusually high fall inflows to Buffalo Bill Reservoir that required corresponding high fall releases, in December, the United States Bureau of Reclamation (USBR) announced that they would be releasing higher than normal flows in the Shoshone River below Buffalo Bill Dam during the winter. On December 20, 2017, USBR adjusted reservoir releases to provide approximately 560 cfs at the Shoshone River gage near Cody, which is about 150 cfs above normal. Based on the most recent, February 1 forecast, projected April through July inflows to Buffalo Bill are 142% of average and necessitate even greater releases to prepare for runoff. As a result, flows out of Buffalo Bill were increased to approximately 810 cfs this week. USBR expects to maintain this flow until the end of February. USBR will continue to coordinate with the Willwood Irrigation District and other cooperating agencies as they plan for additional changes to flows this spring. 

Bathymetric Survey of Sediment Behind Willwood Dam: In late November 2017, WDEQ and WGFD completed a bathymetric survey of the sediment behind Willwood Dam. This information will be used to help quantify changes in the amount of sediment behind the dam as various management activities are implemented. A second survey is expected to occur in 2018 following peak flows on the Shoshone River. Estimates of the volume of sediment behind the dam can be used to help determine how to best manage the deposited sediment while also protecting the downstream fishery.

Turbidity and Suspended Sediment Data Collection Efforts Above and Below Willwood Dam: Last year, WDEQ contracted with the United States Geological Survey (USGS) to install turbidity sensors and other equipment on the Shoshone River upstream (06283995) and downstream (06284010) of Willwood Dam to determine the timing and quantity of suspended sediment coming into and exiting the dam (USGS Scope of Work). The turbidity sensors were operational from approximately mid-October to late December, but had to be taken down due to issues with powering the equipment during the winter months. In December, USGS installed a hydroacoustic device at the downstream site that will be used in conjunction with the turbidity sensor, manually collected flow, and suspended sediment concentration data to develop a relationship that will provide real-time suspended sediment concentrations upstream and downstream of Willwood Dam. See USGS’ January 2018 update for additional information. In the coming months, USGS will be working on getting the turbidity sensors online again and installing a hydroacoustic device at the upstream site. This information will be used to help more effectively manage sediment at the dam and minimize potential impacts to the downstream fishery.

Shoshone River Water Quality Monitoring: WDEQ continues to monitor the water quality of the Shoshone River from Cody to Lovell. Water quality samples are collected at 9 sites every month. In addition, invertebrates and algae were sampled this fall at the reaches that could be safely sampled given the higher than normal flows. WDEQ plans to continue the monthly water quality sampling through 2018 and will collect another round of biological (algae and invertebrates) samples in the fall of 2018. WDEQ’s sampling and analysis plan for this effort is available on the Willwood Dam and Shoshone River Project page.

Willwood Work Group 3 Update: Work Group #3 has been meeting regularly over the past eight months to address potential sediment sources into the Shoshone River and its tributaries upstream of Willwood Dam. Most importantly, Work Group #3 is working to identify potential sediment reduction projects and connect landowners, agencies, and organizations interested in voluntarily implementing such projects with technical and financial resources. The work group is discussing monitoring activities that would help the group achieve its objectives, with some preliminary sediment samples collected by WGFD on two tributaries in 2017. The group is also discussing public outreach activities that will help support sediment reduction efforts in the watershed. A second field tour is tentatively being planned for June 2018 as part of outreach activities. The work group has also started to draft a watershed plan that will summarize the findings and recommendations of the work group. If you are interested in participating on Work Group #3, please contact the Powell Clarks Fork Conservation District at 307-754-9301 or Jennifer Zygmunt, WDEQ, at 307-777-6080 for more information about future meetings.