Le Sueur River Watershed - Rivers and Streams
The Le Sueur River flows 111 miles beginning in Freeborn County, and outlets into the Blue Earth River. Major tributaries include the Big Cobb River, Little Cobb River, Maple River, and Rice Creek. The total distance of the stream network is 1,201 miles of which 703 miles are intermittent streams and 498 miles are perennial streams.
Public and private drainage systems, lakes and wetlands also feed the Le Sueur River. The Le Sueur River Watershed is extensively drained through a vast ditch system. Through the county ditch system, these public ditches are privately owned but publicly managed systems. Total, there are 119 public drainage systems covering 369,337 benefitted acres. This includes 285 miles of open ditch and 616 miles of tile.
Flows within the Le Sueur River have increased which influences pollutant loading and channel conditions. Over the last 60 years, river flows have roughly doubled (MPCA, Le Sueur River WRAPS Report). This is a result of altered hydrology and decreased evapotranspiration. With an increase in flow, we also see an increase in nitrogen delivered from tile and shallow groundwater, an increase of phosphorus, and an increase of suspended sediment in streams from bank erosion. Sediment is an ongoing issue within the Watershed. Approximately 24-30% of the total suspended solids (TSS) entering the Minnesota River comes from the Le Sueur River (An Integrated Sediment Budget for the Le Sueur River Basin). A vast majority of the TSS is from non-point sources, including channel sources, ravines and gullies, and uplands.