Soil erosion and sedimentation are the largest pollutants by volume of Minnesota's lakes and streams. Soil erosion consists simply of the availability, detachment and transport of soil particles into a lake or stream. Soils can reach the lake from direct shoreland erosion or in water flowing into the lake that has received soil particles from stream bank erosion or erosion within the lake's watershed. Erosion affects nearly all watersheds, although the source and degree of impact may differ greatly.
Agriculture is the main source of sediment in much of the state.
In the central and northern parts of the state, commercial and residential development are concerns. Roads are of concern in other areas. The amount of eroded soils reaching a lake is directly proportional to the distance of the erosion source from the lake. Shoreland erosion can have nearly a 100 percent sedimentation delivery rate. Much of the soil eroded into flowing water falls out, or is deposited as sediment, before reaching a stream.