Big Green Lake Impairment Status

What is the Big Green Lake impairment?
Big Green Lake was listed as impaired in 2014. The impairment is for unacceptable levels of Dissolved Oxygen at the lake’s Thermocline. The Thermocline is the area of the lake where the warm water meets the cold water, this is generally at a depth of 30 to 50 feet down from the water’s surface. The State of Wisconsin lists the primary cause of this impairment as too much phosphorus in our lake.

Why is the Big Green Lake Impairment Important?
Some people may say: “Why should I care about something that happens for approximately one month per year (late summer) and doesn’t affect my enjoyment of the lake (can’t even see what’s happening 50 feet below the water’s surface)”. The answer is multifaceted: First, low levels of Dissolved Oxygen affect living organisms (i.e. fish) and their ability to live and survive in the Low Dissolved Oxygen Zone. Second, even though the “Low Dissolved Oxygen Impairment” isn’t something new (this phenomenon has been in Big Green Lake for over 100 years and it exists in other lakes as well), it has gotten worse over the past couple decades and it can be a sign of other troubles with our lake.

What is being done to fix the Big Green Lake Impairment?
Our Lake Management Planning (LMP) Team along with some of the State’s best limnologists and biologists have been studying this phenomenon for the past several years and we believe we are on-track to discover the more detailed reasons for our problem in the next 12-24 months as we conclude the Low Dissolved Oxygen Study currently underway on our lake. Once we understand more of the specifics, we can better target our
corrective actions and lake improvement strategies to improve our low oxygen levels back to acceptable state criteria levels in the next 5-10 years.

Isn’t it inconsistent to call Big Green Lake a World-Class Lake if it’s impaired?
No, Big Green Lake is an outstanding water body with relatively low levels of phosphorus when compared to other Wisconsin lakes. Nevertheless, our LMP Team needs to return all of our lake’s water quality key measurements (Secchi, Chlorophyll, Phosphorus, Dissolved Oxygen) back to acceptable State of Wisconsin criteria and pending the results of our current Low Dissolved Oxygen Study, we believe we can more accurately understand our impairment causes and return our lake to acceptable water quality measurement levels within the foreseeable future.

Is there any Good News relating to our impairment?
Yes, on many fronts. First, being listed as impaired has allowed us to tap into many sources of funding (for protecting and improving our lake) to work on many good projects and improvements to our lake. We have invested millions of dollars over the past several years and our plans are to continue with our improvement activities for many years to come. Second, our impairment has brought many of our State’s lake experts “to the table” and we are all comfortable that we are doing everything possible and making progress to both better understand and correct our impairment. Our lake is a huge water body and changes (both good and bad) occur very slowly, the average person won’t notice anything differently about Big Green Lake over the next 10 years even as we continue to make relatively aggressive improvements as outlined in our current Lake Management Plan.