The Nature Conservancy Thinking Outside the Banks with Centennial Valley Project

Last week the Beaverhead Conservation District (BCD) approved a 310 permit for The Nature Conservancy (TNC) on Middle Creek in the Centennial Valley. TNC’s plan is to place around 20 manmade brush structures in the stream channel to slow down flows so that they will begin to access side channels and raise ground water levels. The potential benefits of interest to researchers include enhancement of late season flows, cooled stream temperatures resulting from groundwater exchanges, reductions in sediment loading, and improvement of wetland habitat for wildlife. Middle Creek is a tributary of West Creek – which flows into the Red Rock River about one mile above Lima Reservoir. The project area runs through a section of land TNC has owned since 2009, and currently leases to southern Beaverhead County ranchers for summer grazing.

A 310 permit was required because according to state law, any person proposing a project that may physically alter or modify the beds or banks of a perennial stream, river, or spring must first be granted a permit from their local conservation district. The BCD expressed concern about the potential for the brush structures to cause bank erosion, and stipulated design modifications to direct water away from the banks. They also stipulated that TNC attend a future BCD meeting to report on their findings. The brush structures will likely be installed in May and are expected require annual maintenance until the stream is reconnected to its floodplain through a slow process of bed aggradation. When energy of spring runoff is dissipated across the floodplain, vegetation can reestablish, and maintenance may no longer be needed.

The research team for this project includes representatives from University of Montana Western, Montana State University, Montana Bureau of Mines and Geology, The Nature Conservancy, Wildlife Conservation Society, Montana Fish, Wildlife & Parks, US Fish and Wildlife Service, Montana Department of Environmental Quality, and consulting geomorphologists, ecologists, and hydrologists. This week, several of these researchers gathered in the Centennial Valley to visit the Middle Creek project site. They also visited the site of another similar project on Long Creek, on land owned by J Bar L Ranch. The design of the Long Creek project involves a flume-like feature constructed out of rock and sod, and it is evident that it has been effective at raising the groundwater table.

The Beaverhead Watershed Committee will be closely monitoring the developments in these projects. They have relevance for drought resiliency, Total Maximum Daily Loads (TMDLs), and the Beaverhead Watershed Restoration Plan. It will be very important for all stakeholders in our watershed to be aware of the benefits and drawbacks learned through this research. For more information on this research, feel free to contact the Beaverhead Watershed Committee.

Researchers visit TNC's Middle Creek project site on the north side of the Centennial Valley in Beaverhead County.
Researchers visit TNC’s Middle Creek project site on the north side of the Centennial Valley in Beaverhead County.
Researchers observe the rock and sod flume-like structure on Long Creek in the Centennial Valley
Researchers observe the rock and sod flume-like feature on Long Creek in the Centennial Valley.