Water Storage in the Minnesota River Basin HUC8-Scale Water Storage Opportunities and Mapping Recommendations: Report 1D

The Minnesota River Basin Sediment Reduction Strategy has established a goal to reduce sediment in the Minnesota River by 50 percent by 2030. The strategy also suggested flow reduction targets of 25% (reduce peak flow by 25% and duration of peak flow by 25%). Conservation practices that mitigate sediment erosion, such as reduced tillage and cover crops, support progress towards the sediment reduction target. However, recent studies have shown that a larger source of sediment loading is a result of erosion of near-channel sources during high-flow periods. Water storage practices can further enhance progress towards Sediment Reduction Strategy goals by detaining or retaining water during critical flows to reduce sediment scouring and transport. Water storage can also be beneficial for reducing nutrient loss to waters, reducing floods, meeting local water management goals, and more. The broader objective of this project seeks to identify and evaluate the benefits of potential water storage opportunities in the Minnesota River Basin (MRB). The goals of this phase of the MRB water storage project were to implement previously developed technical approaches at the scale of two subbasins in the MRB and make recommendations for water resources managers to site and map water storage opportunities. The two previously developed technical approaches are for (1) siting opportunities for water storage practices using geospatial analyses and (2) estimating the likely ranges of potential water storage volumes from the identified practices. This report presents the results of the siting and volume estimates for the Le Sueur and Cottonwood subbasins and provides recommendations for water resources managers for siting and mapping water storage practices at smaller and larger scales. Additional phases will quantify the estimated cumulative effects of water storage practices on peak and annual flows for a few major tributaries to the Minnesota River.