Impaired Water - Clear Lake (Clear Lake)
Rock County, Wisconsin
LR11
775000
77.41
Water is impaired due to one or more pollutants and associated quality impacts.
Notes
This lake was originally listed as impaired in 1998 due to mercury contaminated fish tissue and is proposed for removal based on 2001 updated Fish Consumption advisories.

This lake was assessed for phosphorus and algae in 2010, 2012, 2014, 2016, 2018, and 2020; an impairment for phosphorus, excess algal growth, and eutrophication was first found in 2010 and have been confirmed in subsequent years.
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
2010-12
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
This lake is recommended for listing in the 2010 cycle. Per Susan Graham, lakes biologist, Clear Lake is a fully enclosed lake with no outlet or inlet, and should be categorized as a deep seepage lake (the automated system assigned it to the deep headwater category, which is incorrect). Its average Total Phosphorus concentration is .048 mg/l which exceeds the impairment threshold of .02 mg/l for deep seepage lakes. Its average TSI based on chlorophyll is 61 which is Fair for deep seepage lakes (63 is the threshold for Poor); however per Susan this lake is impaired due to its eutrophic condition. Two decades ago Clear Lake had a healthy aquatic plant community; now it is full of Eurasian Water Milfoil & curly leaf pondweed (CLP). When the CLP decays in early to mid summer, the water turns green with algae. They have been harvesting for CLP over the last 5 yrs. A study was done on water quality, but it didn't clearly delineate where the pollutant sources are; however the sources are likely anthropogenic; all the homes around the lake have old septic systems. In the last couple of years the lake has also experienced extremely high water levels that have been unprecedented in the last 100 years. The extremely high water level is a big issue for this lake, putting homes in jeopardy; pumping is needed but is cost-prohibitive. The lake is connected to groundwater and elevated groundwater levels associated with weather patterns may the cause of the lake's high water levels. There is concern about removing old septic systems before the groundwater reaches them and causes further contamination. The Lake Association has been active in trying to secure grants.
Date
10/21/2009

Impaired Water Notes
This water was assessed during the 2012 listing cycle, and total phosphorus and chlorophyll sample data exceed 2012 WisCALM listing thresholds for the recreation use.
Date
6/17/2011

Impaired Water Notes
This water was assessed during the 2014 listing cycle; chlorophyll sample data exceed 2014 WisCALM listing thresholds for the Recreation use, however, total phosphorus data do not exceed (nor clearly meet) REC thresholds. Total phosphorus and chlorophyll data do not exceed Fish and Aquatic Life thresholds.
Date
3/24/2014

Impaired Water Notes
This water was assessed during the 2016 listing cycle; chlorophyll sample data exceed 2016 WisCALM listing thresholds for the Recreation use, however, total phosphorus did not exceed REC thresholds. Total phosphorus and chlorophyll data did not exceed Fish and Aquatic Life listing thresholds.
Date
10/19/2015

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. Based on the most updated information, no change in existing impaired waters listing is needed.
Date
6/14/2019

 
Pollutant
Mercury
Listed For
Impairments
Mercury Contaminated Fish Tissue
Current Use
Listing Status
Deletion
Attainable Use
Priority
Not Applicable
Designated Use
303(d) ID
85
Listing Date
4/1/1998
Impaired Water Notes
This listing was part of a set removed from the impaired waters list due to a change in fish consumption advisory levels in 2001. In 2001 Wisconsin DNR put into effect a statewide fish consumption advisory for mercury due to atmospheric deposition. Most of the lakes removed from the specific fish consumption advisories list in 2001 were not removed from the impaired waters list even though the thresholds had changed. For the 2020 assessment process WDNR requested delisting of 91 waters with residual mercury listings from prior to 2001. This request was approved by US EPA.
Date
9/4/2018