The Montana Department of Environmental Quality (DEQ), Montana Fish, Wildlife and Parks (FWP), and the Bureau of Reclamation (BOR) are monitoring several parameters that may have contributed to severe turbidity and algae blooms in Clark Canyon Reservoir and the Beaverhead River. Data collection began in 2014 and is still being collected.

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 monitors 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 depending on clarity of the reservoir and basin. DEQ also has deployed 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 2016. 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.

FWP continually monitors fish population and condition in the reservoir and the Beaverhead River, and assesses whether there are any observable impacts as a result of the clarity problems.

In February of 2017, DEQ presented their findings from two years of data collection. BWC hosted a public meeting where DEQ addressed what they think is the cause of the algal blooms. To learn more about the issues present in Clark Canyon Reservoir, please visit DEQ’s website here to review their presentations. Since this meeting, BWC has created a turbidity solutions committee to address the turbidity events in Clark Canyon Reservoir. The committee is made up of a diverse group of volunteers representing all stakeholders within the watershed. The goal is to provide solutions to tackle algal blooms in the reservoir by 2018.

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.

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

Monitoring Strategy Flow Chart

Monitoring Framework Spreadsheet

2016 DEQ Sampling and Analysis Plan

2017 DEQ Turbidity Findings

Montana Outdoors Magazine Issue on Clark Canyon Reservoir

To report concerns regarding this issue, please email