The Minnesota River drains about 17,000 square miles in Minnesota, Iowa and South Dakota. In Minnesota it drains about 15,000 square miles in Minnesota, encompassing 37 counties . The Minnesota basin is subdivided into twelve major watersheds covering about 9,570,000 acres in Minnesota, and these are further subdivided into 1113 minor watersheds.
The Minnesota River basin encompasses a diverse range in climate, hydrology, landscape, and soils (click here for a table). Annual precipitation ranges from 22 inches in the northwestern basin to 32 inches in the southeastern portion of the basin(click here for a map of avg. annual precipitation). Annual runoff ranges from 2 inches in the west to 6 inches in the east, largely in response to patterns in precipitation, land use, slope steepness, soil freezing, and soil recharge.
The basin encompasses 27 geomorphic units with distinct differences in topography, landscape, hydrology, and soil properties (click here for a map of geomorphology)(click here for a statistical summary). There are seven distinct slope steepness classes including complex topography with slopes ranging from 6-45% in steepness, to flat landscapes with slopes ranging from 0-2% in steepness (click here for a map of slope steepness groups )(click here for a statistical summary).
Water and wind erosion potentials of agricultural cropland from water erosion vary across the Minnesota River Basin (click here for a map of water erosion potential), and (click here for a map of wind erosion potential). These patterns are affected by changes in slope steepness, soil parent material, and climate.
Internal soil drainage ranges from well drained to poorly drained, with extensive tile drainage in poorly drained soils of the basin ( click here for a map of internal drainage) (click here for a statistical summary ). Hydrologic features include lakes, wetlands, rivers, permanent streams, intermittent streams, and drainage ditches.
Agricultural land in the Minnesota River basin differs in its potential to deliver pollutants to various waterbodies partly as a function of its proximity to water.
Since the Minnesota River Basin is relatively young in geologic time scales, sediments deposited during recent glacial recessions are continuing to be eroded. Erosion of banks along streams and rivers may be particularly important where rivers have narrow flood plains and steep banks (click here for a map of steep lands next to rivers and streams).
Land within a quarter mile of waterbodies is often a primary target for incentive programs to improve upland agricultural management (click here for statistical summary of land near waterbodies ). The targeting process also often considers the slope steepness of land next to permanent streams and rivers, which has been summarized for each of the twelve major watersheds in the Minnesota River basin (click here for statistical summary of steep land next to permanent streams).
These physical and hydrologic features influence the types of agricultural management practices that are adopted in specific portions of the basin. They also influence the type, magnitude, and seasonal pattern for production of non-point source pollution.
