Minnesota River – Mankato Watershed Total Maximum Daily Load Study

The Clean Water Act (CWA), Section 303(d) requires total maximum daily loads (TMDLs) to be produced
for surface waters that do not meet applicable water quality standards necessary to support their
designated uses. A TMDL determines the maximum amount of a pollutant a receiving waterbody can
assimilate while still achieving water quality standards and allocates allowable pollutant loads to various
sources needed to meet water quality standards. This TMDL study addresses the stream and lake
impairments in the Minnesota River–Mankato Watershed in south-central Minnesota. The causes of
impairment in the watershed include high levels of Escherichia coli (E. coli), total suspended solids (TSS),
nitrate, and total phosphorus (TP), affecting aquatic life, aquatic recreation, drinking water, and limited
resource value designated uses. Forty-three stream TMDLs and eight lake TMDLs are provided: 34 E. coli
TMDLs, 6 TSS TMDLs, 3 nitrate TMDLs, and 8 phosphorus lake TMDLs.