The Montana Department of Environmental Quality is in its third year of working with Montana Fish, Wildlife & Parks, and the Bureau of Reclamation to find solutions to turbidity problems in the Beaverhead River downstream of Clark Canyon Reservoir. In Spring 2016 DEQ began monitoring several parameters that may have contributed to severe turbidity and algae blooms in Clark Canyon Reservoir and the Beaverhead River over the summers of 2015 and 2016. The river again turned turbid in late July and over the first weeks of August, 2016.
FW&P is studying the response of fish populations to elevated turbidity in the Beaverhead River. BOR has conducted a thahymetric study of the reservoir, including the area of the "dead pool" near the outlet works. This is an effort to better understand the buildup of sediment within the reservoir. DEQ and BOR also compared 2014 and 2015 reservoir storage, state, and discharge to the Beaverhead to historical conditions and dam operations and found no operational anomalies.
DEQ's efforts for 2017 are primarily designed to further understand the source areas and mechanisms of particle resuspension in the reservoir and to understand ho far downstram water clarity is being affected. A number of specialized studes will provide information that will support planning to fix the problem.
FW&P and dam operator BOR initiated in early May, 2017 a Beaverhead River Flushing Event to mobilize fine sediment deposited in the river, largely by Clark Canyon Creek. Natural volcanic geology surrounding Clark Canyon Creek is the primary sediment source, according to the report. The flushing event was initiated on May 5 and concluded on May 8. Discharge was increased from winter releases of 43 cubic feet per second to 600 cfs over the 36-hour period. Full Study.
A Press Release notes DEQ has monitored for nutrients, common ions, total dissolved solids, total suspended solids, volatile suspended solids, oxidation reduction potential, and phytoplankton in Clark Canyon Reservoir in addition to the streams mentioned above. Monitoring of these parameters increased in frequency as the clarity issues began to reoccur the summer of 2016.
A public meeting was held on February 7, 2017 in Dillon. A joint presentation by Montana DEQ, FW&P, and the Bureau of Reclamation addressed the following:
- Current understanding of the chronology of the turbidity in the Beaverhead River and the reservoir.
- Review of data collected during the past two years and how it compares to historic information, including identification of the turbidity material and minerology.
- Analysis and interpretation of potential mechanisms causing the turbidity. A review of the importance of factors like water movement and reservoir mixing, whether fish and other biota contribute to the turbidity, and geochemistry that could further exacerbate such events.
- Potential effects on fish and other aquatic life.
- Potential next steps.
Presentations from the February 7, 2017 Public Meeting in Dillon include one by Montana DEQ followed by one from FW&P.
Montana Outdoors magazine published an article on the collaborative effort in the May/June 2017 issue.
Montana DEQ also held a Public Comment Period in spring 2016 for a Section 401 Water Quality Application for a proposed Hydroelectric Project on the dam at Clark Canyon Reservoir.
Clark Canyon Dam is a Bureau of Reclamation facility designed for irrigation and flood control. The proposed hydroelectric facility is being forwarded by a private company and would be a run-of-the-river retrofit to the existing dam and would operate under existing withdrawals and flows.