EPA Could Declare Lake Of The Ozarks An ‘Impaired Waterway’… Here’s Why


Lake of the Ozarks holds an estimated 83 trillion cubic feet of water, boasts 1,150 miles of shoreline, and is one of the most popular boating destinations in the Midwest. From fishing to swimming, wakesurfing to coving-out, millions of people enjoy the waters of Lake of the Ozarks every year. But is the Lake of the Ozarks ecologically impaired? The Environmental Protection Agency (EPA) thinks so, and they say the culprit is chlorophyll.

The EPA is in the process of adding the Lake of the Ozarks to the Department of Natural Resources (DNR) 303d list of impaired waters after levels of chlorophyll-a were found in the water in 2017 that exceed the EPA’s impairment threshold. The Lake’s chlorophyll-a levels were below the EPA’s impairment threshold in 2016 and 2018.

But before an official decision is made, the EPA is seeking out public comment.

The Department of Natural Resources compiles the 303d list of impaired waterways every two years as part of the requirements of the federal Clean Water Act. Originally, DNR had not included Lake of the Ozarks on the state’s list of 481 impaired waterways, but the EPA partially disapproved the state’s decision and has added an additional 40 waterways to the list, including the Lake of the Ozarks. 

And while the designation “impaired waterway” can sometimes indicate a water quality issue that is harmful to humans, it can also label a lake that has a more innocuous environmental issue. In the case of the Lake of the Ozarks, the EPA says tests revealed levels of chlorophyll-a above the EPA’s threshold. Chlorophyll-a is used to measure the amount of algae in a body of water and, although algae is a natural occurring part of freshwater ecosystems, high algae levels can cause green scum, low oxygen levels and, in extreme cases, fish kills. 


“The impairment for Lake of the Ozarks is related to Aquatic Life not Human Health,” said an agency spokesman for the EPA. 

For a body of water to hit the threshold for impairment, samples need to show 15 ug/L, or 15 micrograms per liter, of chlorophyll-a. The measurement of a microgram per liter is approximately equivalent to one part per billion in a body of water. 

“A way to visualize one part per billion (ppb) in water is to think of it as one drop in one billion drops of water or about one drop of water in a swimming pool,” according to a brief put out by Kansas State University about units of measurement in environmental reports. 

The Lake of the Ozarks exceeded the impaired threshold in 2017 with a mean of 16.31 ug/L, only 1.31 ug/L over the impairment threshold. Tests in 2016 and 2018 were well-below the threshold, at 10.07 ug/L and 6.15 ug/L respectively. However, water samples weren’t the only thing taken into account for this assessment.

“Multiple fish kills occurred in the lake during this period and in 2018, the Missouri Department of Conservation noted that low dissolved oxygen levels killed over 100 fish,” said an agency spokesman for the EPA.

LakeExpo reported on the fish kills in 2018, but Missouri Department of Conservation specialists downplayed their significance at the time. MDC Fisheries Regional Supervisor Craig Gemming explained algae flourishes when the weather is warm and it hasn’t rained in awhile; then when algae dies it consumes Dissolved Oxygen (DO), thus reducing the DO levels for fish nearby. The oxygen levels soon normalize, but sometimes not before a batch of fish go belly-up. Gemming emphasized the process is natural and happens every year. MDC Biologist Greg Stoner pointed out in that 2018 interview with LakeExpo, “It looks like a lot of fish, but it’s a drop in the bucket compared to what’s out there.”

Fish were pushing up daisies quite a bit in June on Lake of the Ozarks, according to a Misso…

Local Response

Local response to the EPA has been mixed. Greg Hasty, presiding commissioner of Camden County, said in a press release that the EPA’s decision was more motivated by money than by genuine concerns over water quality. 

“Our Lake of the Ozarks is clean. In fact, it is very clean. The fish love it here. We have one of the most highly regarded fisheries in the United States. Ask any angler,” Hasty contended.

Donna Swoll, executive director of the Lake of the Ozarks Watershed Alliance, found the findings to be comparatively minor. 

“If you have two [exceedances], two things that go out of whack a little bit, in a three-year period, then you can be considered for the list,” Swoll explained. “And what happened to us is that we had a very small fish kill, which just happens from time to time, it’s a normal thing. The other thing that happened is that we had a little bit of high algae at the dam. Now our Lake is 55,000 acres, so they have two little things happen in a small area. It’s very insignificant.”

Swoll went on to say that it’s important to remain vigilant about water quality issues and that catching issues when they’re minor is a way to stop them from getting worse. 

“Once we look at the science, it gives us the opportunity to catch something way ahead for time before something really goes bad and take positive action and be proactive and keep our Lake healthy,” Swoll said.

What Happens To An Impaired Waterway?

Step #1 – A Total Maximum Daily Load — or “pollution limit” — is established

“Once a waterbody is listed, MDNR (Missouri Department of Natural Resources) develops a priority schedule to develop a Total Maximum Daily Load (which is a pollution budget of point and non-point sources, plus a margin of safety) to address the impairment,” an EPA spokesman explained. 

The Total Maximum Daily Load (TMDL) is “a calculation of the maximum amount of pollutant allowed to enter a waterbody so that the waterbody will meet and continue to meet water quality standards for the particular pollutant.” So in the case of the Lake of the Ozarks, the TMDL would calculate the maximum amount of chlorophyll-a allowed in the Lake of the Ozarks for it to still meet water quality standards.

The exact calculation varies for different bodies of water depending on the intended purpose of the body of water. A lake that is used for swimming and fishing will be held to a different standard than a wildlife conservation area.

Once the TMDL report is written by DNR, it’s sent to the EPA for approval.

Step #2 – EPA & DNR form a plan to reduce the pollutant (in this case, algae)

If the TMLD report is approved by the EPA, the agency sends it back to DNR, and it is implemented to reduce pollution. The report will look at the potential causes of pollutants and determine a reduction target. High levels of algae are often caused by nutrient pollution that can be traced back to agricultural run-off, fossil fuels and fertilizer run-off.

Step #3 – Regulatory, non-regulatory, or incentive-based…


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