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Water Quality

The effort to protect Lac Courte Oreilles is backed by the best science available. COLA has partnered with established, independent experts in the fields of limnology, water conservation, and land and soil impacts. A few examples follow.


Wisconsin’s Consolidated Assessment and Listing Methodology (WisCALM), from the WDNR, provides guidance on assessment of water quality data against surface water quality standards and for Clean Water Act reporting on surface water quality status and trends.

The 2014-2018 LCO water quality assessment based upon the WisCALM protocol is now available. The essential messages from this update are:

1) Based upon total phosphorus concentration, algae growth, water clarity and dissolved oxygen level, the water quality in Musky Bay continues to improve. Recall that the East Bog closed system was placed into operation in Spring 2014.

2) Based on these same factors, the water quality in greater LCO continues to deteriorate. The current total phosphorus criteria for LCO is 15 ppb. LimnoTech notes that for the first time “average TP concentrations in LCO exceed criteria in some portions of the lake.” In addition, LimnoTech states, “the update of the WisCALM assessment for LCO, using data for the most recent five years (2014-2018), confirms impairment of the two-story cold-water fishery habitat for cisco and lake whitefish. The measures of the minimum oxythermal habitat band demonstrate the impairment of this beneficial use.  

The other take a ways from the 2018 assessment are that continued data collection in LCO is critically important; understanding and addressing the drivers of the impaired oxythermal habitat for cisco and lake whitefish is high priority; and a site-specific (SSC) TP criterion protective of the two-story cold-water fishery in LCO is needed.

Assessing waterbodies against water quality standards and identifying impaired waters that don’t meet standards is part of the overarching federal Clean Water Act (CWA) framework for restoring impaired waters. See more details about WisCALM on the WDNR website.

Protecting Two-Story Lakes: A Battle Against Phosphorus and Climate Change

Hans Holmberg

Hans Holmberg

Hans Holmberg, a Senior Engineer and Associate Vice President with LimnoTech, gave this presentation at the 2017 Minnesota Water Resources Conference held at the Saint Paul River Centre in Saint Paul, Minnesota, on October 17-18, 2017. This conference is one of the largest conferences of its type in the country - attendance in 2017 was probably in the 7-8 thousand range - and it drew scientists from around the world.  

Hans presented the work undertaken by LimnoTech at COLA's and the LCO Tribe's direction to establish the link between phosphorus concentration and oxythermal habitat for two-story lakes. This is the cutting edge research underpinning the need to list all of LCO as an impaired water and to assist the WDNR's rule-making process establishing a protective site specific phosphorus criterion for LCO ... to say nothing about helping out the cisco and whitefish in the lake.


Total Maximum Daily Load Study, Site Specific Criterion Proposal & More

Click on the photos at the bottom of the page to learn more about:

  • COLA's and the LCO Tribe's Total Maximum Daily Load study and Site Specific Phosphus Criterion proposal, which detail how COLA has worked with the LCO Tribe and LimnoTec, to compile and assess water quality data over many years.

  • How phosphorus pollution coming from Musky Bay is now affecting all of the West Basin of LCO.

  • Why COLA's science led to the listing of Musky Bay as an impaired water in 2014 and the likely listing for the entire lake in 2018.

  • How rare and precious is LCO's two-story cold-water fishery.

  • The historical timeline detailing the challenges facing LCO.

Please take a look at our highest-priority initiatives and accomplishments.

recent threats

Blue-green algae bloom

When a lake looks like pea soup, that’s the effect of a blue-green algae bloom. A first-ever bloom of this kind developed on Stuckey Bay on or about Sunday, November 6, 2016 and lasted for five days.

Fish die-off

In October 2016 there was a massive die-off of whitefish and cisco in LCO. Poor water conditions choked off the rare habitat. See a comprehensive report here.



Issue 2  Saving the lake

Issue 3  COLA takes another giant step in stewardship

Issue 8  'Lac Courte Oreilles - a rare gem'

Issue 13  ‘Death by a thousand cuts,’ Chairman Mic Isham’s focus on water quality, environment'

Issue 31 ‘The Painted turtle: Now we know’