Watonwan River 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 water body 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 Watonwan River Watershed in south central Minnesota. The causes of
impairment in the watershed include high levels of Escherichia coli (E. coli) and total phosphorus (TP),
affecting aquatic recreation designated uses. Ten E. coli TMDLs for streams and four phosphorus TMDLs
for lakes are provided. Stream impairments related to sediment are being addressed in a separate
concurrent report.