The little minnesota river browns valley diversion fish passage improvement project is looking to address deficiencies that have developed from a flood diversion project in 2010

The Department of the Interior Fish and Wildlife Service Region 6 awarded a $750,000 Cooperative Agreement to the State South Dakota Game Fish & Parks Wildlife Division under the National Fish Passage program (CFDA 15.685). This funding will support the Little Minnesota River Browns Valley Diversion Fish Passage Improvement Project. The project aims to address fish passage barriers created by a 2010 flood diversion project that limited fish movements and spawning in the Little Minnesota River and its tributaries. The project will construct a rock arch rapid with a low flow channel to restore connectivity and enable full access to 75 miles of upstream river habitat for walleye, lake sturgeon, and over 40 other native fish species. This connectivity is critical for the success of the lake sturgeon reintroduction effort underway in the region. The project is scheduled for completion by September 30, 2027.

The flood diversion was done to mitigate continual flood events that were damaging to the town of browns valley, MN. A levee and box culvert were installed to limit flows of water in the original channel through town and divert excess waters through a diversion channel around town, which severely restricted or eliminated fish passage during certain flow events. This fish passage barrier has been detrimental specifically during spring flows which restrict or eliminates fish movements during the critical times of fish movement and spawning events. The sisseton-wahpeton oyate tribe, which lies upstream of the flood diversion, initiated an assessment to investigate fish passage at the diversion site since historical walleye spearing returns upriver, which the tribe uses for subsistence, had been greatly diminished since installation of the diversion. The project is also important because IT will restore longitudinal connectivity between the little minnesota river, IT S tributaries and bigstone lake. Connectivity will restore access to 50 river miles from the project location upstream to the headwaters of the little minnesota river as well as another 25 river miles of the jorgenson river, which is a major tributary just upstream of the project location. This connectivity will not only benefit walleye but will be instrumental in the success of the lake sturgeon reintroduction effort that is underway. Lake sturgeon are a species of greatest conservation need and the connectivity will open critical habitats for their entire lifecycle. There are 3 other species of greatest conservation need along with 6 species of interest and over 40 other native fishes that will benefit from this project. The project will address the fish passage barrier by constructing a rock arch rapid with a low flow channel to increase the frequency at which the diversion channel can be utilized. Modeling for this design has shown the project will eliminate any fish passage barrier while meeting the constraints for the 100-year and 1.4-year discharge events through browns valley. Rock arch rapid fishways, when constructed according to strict design principals, have proven to be stable and long-lasting. They are also capable of withstanding extreme environmental events. Rock arch rapids have been used in numerous locations and have proven to restore full fluvial function. They have also proven effective for fish passage of all life stages of native fish species upstream and downstream.