The Minnesota River Basin (MRB), a natural observatory utilized by the REACH project, covers 44,000 square kilometers in the Upper Mississippi Watershed. The MRB contains an exceptionally wide range of environments, including flat agricultural lands, as well as steep ravines and tall, rapidly eroding bluffs. It has been cited as one of the most polluted rivers in the nation, with sediment and nutrients being the primary pollutants of concern. The basin includes an extensive network of agricultural ditches and sub-surface drain tiles, as 80% of the basin is used for agriculture, primarily row crops. The MRB is responsible for approximately 85-90% of the sediment delivered to Lake Pepin, a naturally-dammed lake on the Mississippi River, despite the fact that the MRB accounts for a mere 38% of the water discharge to the lake.
- Natural geologic change: 13,400 years ago glacial Lake Agassiz catastrophically drained through the Minnesota River, incising it more than 70 m and establishing many hot-spots of geomorphic change that still impact the river today.
- Climate change: Precipitation and temperature have changed significantly in the MRB over the past century with overall rising temperatures, shifting precipitation patterns and increase in heavy rainfall events.
- Land use change: The MRB has undergone major changes in land use, primarily conversion from prairie, wetland and forest to row crop agriculture.