The summer of 2022 was beautiful on Big Green Lake. The minimal snow cover in our area last winter caused limited spring runoff to the lake. Additionally, we saw a very gradual warming of the lake itself along with limited spring and early summer rainfall. These factors helped to create better water quality in 2022 than we’ve seen in many years on Big Green Lake.
These observations are reinforced by 2022 USGS water sampling results that showed in-lake phosphorus levels dropped to around 15.5 ppm. In the past 20 years alone, we’ve seen in-lake phosphorus levels as high as 33.8 ppm phosphorus (in 2000) and as low as 13.3 ppm (in 2012). Our 20-year average is roughly 20.8 ppm. It is critical to note that 15 ppm is the DNR’s baseline water quality goal for the lake, though this would need to be sustained over a 5-year period to indicate the lake was meeting the DNR goal. While this year’s data is positive, the GLSD and our lake management partners are realistic about the lack of snowfall/rainfall and the impact these dry conditions had on the lake. The years of 2018 though 2020 were 3 of the wettest years on record and brought significantly higher than average nutrient loading into the lake. We cannot rely on drought years to improve the lake’s water quality. The GLSD and our lake management partners must continue to develop and help fund projects throughout the watershed to limit nonpoint source runoff.
As mentioned above, Big Green Lake’s water levels were again very low throughout the summer. The GLSD fielded calls from residents curious about who controls the level of the lake and why there was still water being allowed over the dam in town. Under Sec. 31.02 of the Wisconsin Statutes, the DNR regulates and controls the level and flow of water in all navigable waters, including the Big Green Lake. Subsequently, the City of Green Lake operates the dam in town and manages the lake level within the range the DNR has established. However, Sec. 31.34 of the Wisconsin Statutes requires that the City of Green Lake maintain at least 25% of the natural flow to the Puchyan River at all times to support aquatic habitat downstream. Therefore, in times of drought, the City of Green Lake is not able to stop the flow of water over the dam in order to increase the level of Green Lake.
Aquatic plant growth was slow to begin for much of the lake early, but dense stands were seen in the usual areas by August. The DNR allows the GLSD to operate our harvesting program from June 1st to August 31st each year. Per the permit, our crews focus their efforts on creating ease of navigation adjacent to piers and boat lifts. Please know that the crews try to meet landowner expectations while adhering to the permit limitations.
As in the past, the GLSD weekly beach sampling program ran from Memorial Day to Labor Day. Every week, GLSD staff sampled at each public beach on the lake as well as several boat launches to determine E. coli levels at these locations. For much of the summer, elevated levels of E. coli were found at the Sunset Park boat launch and for one reading in July, a sample taken at the Dodge Park boat landing showed similar results. Discussions with the WI State Lab of Hygiene and the WI DNR suggest possible impacts from large amounts of goose and seagull droppings washing into the water from the blacktopped/concreted landings. The GLSD will continue to monitor this issue in 2023.