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What are Impaired Waters? 

Impaired Lakes in the Le Sueur River Watershed

Impaired Waters
Assessments: Are waters meeting fishable and swimmable standards?

Watershed Health Assessment Framework - Impaired Waters

During the intensive watershed monitoring phase of the Watershed Approach, state agencies (MPCA and MDNR) collect data about biology such as fish populations, chemistry such as pollutant levels, and flow to determine if lakes and streams were meeting water quality standards designed to ensure that waters are fishable and swimmable. Waters are “impaired” if they fail to meet standards. 

Of the 11 lakes examined in the watershed, two supported aquatic recreation - St. Olaf and Reeds; five were impaired due to high nutrient levels; and four need more data to determine their status.


Of the 74 stream sections examined, only one- in the Cobb River- supported aquatic life; 21 were impaired; 12 need more data to determine their status; and 40 have been altered significantly so the MPCA is deferring assessment. Under federal and state laws, impaired waters must have Total Maximum Daily Load (TMDL) studies to determine reductions of pollutants needed to again meet water quality standards. In this first WRAPS cycle, the MPCA completed TMDL studies for four lakes and six stream sections. In addition to these lakes and stream sections, the MPCA has completed a TMDL study for Lura Lake in the watershed and is working to complete a TMDL study of turbidity in the Le Sueur River as part of the Greater Blue Earth River system.


Source: MPCA Le Sueur River Watershed Watershed Restoration and Protection Strategies  (WRAPS) Report Summary

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