Exploring Fish Passage and Rock Arch Rapids
Minnesota is home to over 150 species of fish, making it a treasure trove of aquatic diversity! As the land of 10,000 lakes, it’s no wonder that fishing is such an integral part of our state’s identity. However, our fish populations are facing some tough challenges due to factors like nutrient runoff into our waterways, extreme weather, and physical barriers such as dams. But there’s good news! We can take action to help. Simple steps like using cover crops and keeping storm drains clear can really make a difference in reducing excessive nutrients. When it comes to dams, we’re excited to share an innovative approach that can boost fish populations.
The Minnesota DNR reports that there are over 1,150 dams in the state. These structures can disrupt rivers and turn flowing streams into still reservoirs, altering the ecosystem in significant ways. This can lead to problems like sediment and nutrient build-up, increased algae growth, higher water temperatures, lower oxygen levels, and hindered fish movement. When fish can’t pass through these dams, it limits their numbers upstream and prevents many species from reaching their spawning grounds, which can hurt their natural reproduction. Moreover, native mussel species that rely on fish as hosts for their upstream journey can't get above the dam either, impacting our biodiversity and water quality.
Fortunately, communities across the state are embracing solutions such as replacing or modifying low-head dams into Rock Arch Rapids. This nature-inspired fish passage design allows fish to swim freely, resembling the flowing stream riffles they thrive in. Picture a series of descending boulders, creating pools of water like a staircase just for fish! Rock Arch Rapids ensure fish can pass under any flow conditions and enhance the natural movement of sediments.
The Willow River dam in Pine County, MN was replaced with rock arch rapids in 2022. Image Source: Pine City Pioneer, Courtesy of the Minnesota DNR.
Rivers are incredibly resilient, and the positive effects of modifying or removing dams can be seen quite rapidly. In fact, the largest dam removal project in U.S. history, the Klamath River project, demonstrated that salmon returned to their historic spawning grounds within just two months of the dams being removed! Besides the ecological benefits of boosting aquatic diversity and restoring sediment flow, Rock Arch Rapids also require little to no maintenance, and even enhance safety for recreational activities. All in all, Rock Arch Rapids are a fantastic conservation tool to keep in our toolkit!
We’re excited to share that we’re partnering with the Minnesota DNR on a fish passage project right here in the Cannon River watershed. Thanks to the State of Minnesota’s Get Out MORE funding, the Gorman Lake Dam in Le Center and the Schmidtke Dam in Morristown will be replaced with the Rock Arch Rapids, detailed in this blog. Stay tuned, as we’ll have more information about this project available on our website soon!