Agencies Mobilizing to Assess Causes of Beaverhead Algae Blooms

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Clark Canyon ReservoirThe Montana Department of Environmental Quality, Montana Fish, Wildlife and Parks, and the Bureau of Reclamation have recently begun monitoring several parameters that may have contributed to severe turbidity and algae blooms in Clark Canyon Reservoir and the Beaverhead River the past two summers.

DEQ has deployed instruments to continuously measure dissolved oxygen, pH, water temperature and turbidity in the Beaverhead River, the Red Rock River, and Horse Prairie Creek every half hour throughout the summer. Each month from May through September, DEQ will be monitoring nutrients, common ions, total dissolved solids, total suspended solids, volatile suspended solids, dissolved oxygen, oxidation reduction potential, and phytoplankton in Clark Canyon Reservoir, the Beaverhead River, the Red Rock River, and Horse Prairie Creek. Monitoring of these parameters may increase in frequency if the clarity issues of the past two years begin to reoccur this summer. DEQ also has a plan to utilize Sontek Doppler Sound Scatter technology to assess whether mobilization of sediment from the reservoir bed is a contributing factor.

Reclamation performed a bathymetric survey of the reservoir bed elevation at the end of April. This will help to assess whether filling of the reservoir dead pool is a contributing factor to the clarity issues. This survey, which was completed by Reclamation technical services personnel from the Great Plains Regional Offices in Denver, was not originally scheduled for this year, but was moved up due to the urgency of the issue. Reclamation performs these surveys on all of its reservoirs every ten to fifteen years, ideally when the reservoirs are full. Clark Canyon Reservoir had been approaching 15 years since the last survey, and Reclamation was forced to perform the survey when the reservoir was less than full. Analyses of the survey will likely be available this fall or winter, after the agency field work season is complete.

FWP will continue to do its routine monitoring of fish population and condition in the reservoir and the Beaverhead River, and will assess whether there are any observable impacts as a result of the clarity problems.

Additional information about these interagency monitoring efforts can be found in the following linked documents:

Monitoring Strategy Flow Chart

Monitoring Framework Spreadsheet

DEQ DRAFT Sampling and Analysis Plan

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