Impaired Water - Magnor Lake (Magnor Lake (Richardson))
Polk County, Wisconsin
SC07
2624600
229.36
Water is impaired due to one or more pollutants and associated quality impacts.
Notes
Magnor Lake was evaluated for phosphorus and algae every two years between 2010 and 2020. Phosphorus levels were found to be too high, which was reflected in algal blooms. This lake is covered by a restoration plan: Implementation Plan for the Lake St. Croix Nutrient Total Maximum Daily Load (expires 2025).
Listing Details
Pollutant
Total Phosphorus
Listed For
Recreation
Impairments
Eutrophication, Excess Algal Growth
Current Use
Restricted Recreation
Listing Status
303d Listed
Attainable Use
Full Body Contact - Swimming, Boating
Priority
Low
Designated Use
Full Body Contact - Swimming, Boating
303(d) ID
2010-5
Listing Date
4/1/2010
Impaired Water Notes
This water was assessed during the 2018 listing cycle; new total phosphorus and chlorophyll sample data exceeded 2018 WisCALM listing thresholds for the Recreation use and Fish and Aquatic Life use.
Date
7/10/2017

Impaired Water Notes
We are proposing Magnor Lake to be listed because both the Total Phosphorus concentrations and TSI scores are elevated above the listing thresholds for this specific type of lake (Deep Seepage). Average Total Phosphorus concentration (2004-2008) is .13 mg/l, which exceeds the listing threshold of .02 for a Deep Seepage lakes. Average TSI based on chlorophyll is 72, which exceeds the threshold of 63 for Deep Seepage Lakes. Furthermore, a paleoecological core collected in 2005 and related diatom analyses by WDNR Research Scientist Paul Garrison indicated that current TP concentrations are not natural, background conditions but rather have gotten worse through time. Relatively recent (2001-2006) monitoring, modeling, and management planning show that there are controllable nutrient sources, including agriculture, shoreline development, and internal nutrient cycling in the watershed and lake.
Date
10/15/2009

Impaired Water Notes
This water was assessed during the 2014 listing cycle; total phosphorus sample data overwhelmingly exceed 2014 WisCALM listing thresholds for the Recreation use, exceeded Fish and Aquatic Life use and chlorophyll data exceeded REC and FAL thresholds.
Date
2/28/2014

Impaired Water Notes
This water was assessed during the 2016 listing cycle; total phosphorus sample data overwhelmingly exceed 2016 WisCALM listing thresholds for the Recreation use, exceeded Fish and Aquatic Life use, and chlorophyll data exceeded REC and FAL thresholds.
Date
10/9/2015

Impaired Water Notes
This water was assessed during the 2020 listing cycle; total phosphorus and chlorophyll sample data exceeded 2020 WisCALM listing thresholds for the Recreation use and Fish and Aquatic Life use. This lake is covered by the following restoration plan and was classified as Category 5W as a result: Implementation Plan for the Lake St. Croix Nutrient Total Maximum Daily Load (2025).
Date
7/24/2019