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Interpreting 2000-2023 Water Quality Data Charts for Round Lakes by Joan Buehrle 

Your first glance at the graphs of Water Quality Data shows you that there is great similarity between Round and Little Round Lakes. The trend lines follow similar patterns across all three graphs. This is easily explained by the fact that both lakes experienced the same weather, use, water levels, and construction patterns over time. These factors profoundly influence the quality of water in our lakes. 

Average annual data for Total Phosphorous, Chlorophyll A, and Secchi Disk Depth (clarity) for the years of 2000 to 2023 were provided by Brett McConnell, the LCO Program Manager for the EPA Section 106 Water Monitoring Program. These 3 measures, when examined together, determine the trophic status of a water body, and establish scores called the Trophic State Index (TSI). TSI scores place the waterbody in the category of oligotrophic, mesotrophic, eutrophic, or hypereutrophic. In 2023, measurements for Phosphorus, ChlorA and Secchi Depths provide categories whereby: 

TSI scores of < 38 are in the oligotrophic category
TSI scores of 38-50 are in mesotrophic category
TSI scores of >50 are in the eutrophic/hypereutrophic category. 

To aid you in determining what this means for Round and Little Round Lakes, I have copied this interpretive guide from the DNR’s website. Using this resource will help you understand the water quality data from our lakes. 

Interpretive Guide to the Citizen’s Lake Monitoring Network Water Quality Reports (Taken from the WI DNR website)
Oligotrophic vs. Mesotrophic vs. Eutrophic 

Your trophic state index (TSI) score places your lake into a category of oligotrophic, mesotrophic, eutrophic, or hypereutrophic. Lakes naturally occur in each of the first three categories, but hypereutrophic lakes are within that category because of human-caused nutrient enrichment. Below is a short description of each category. 

Oligotrophic lakes are generally very clear, deep, and cold. The lake substrate is typically firm and sandy. Nutrient levels are low, so the lake generally does not support large populations of aquatic plants, animals, or algae. The fish that occur in oligotrophic lakes are often low in abundance, but large in size. Many oligotrophic lakes divide into two layers in the summer, a condition known as stratification. The lower layer, called the hypolimnion, is cold and supports cold-water specialist fishes, like lake trout and cisco. These species require cold temperatures and high oxygen levels, so they remain in the lake’s lower level throughout the summer. 

Mesotrophic lakes contain moderate amounts of nutrients, and contain healthy, diverse populations of aquatic plants, algae, and fish. Occasional algae blooms may occur. If the lake is deep enough to stratify, the hypolimnion often becomes low in oxygen by the end of summer and may result in some phosphorus release from the sediments. 

Eutrophic lakes are high in nutrients and contain large populations of aquatic plants, algae, and fish. The lake substrate is typically soft and mucky. The aquatic plants and algae often grow to nuisance levels, and the fish species are generally tolerant of warm temperatures and low oxygen conditions. Common fish species include carp, bullheads, and bluegills. If the lake is deep enough to stratify, the hypolimnion is usually very low in oxygen by mid-summer. This results in a release of phosphorus from the sediments, which can fuel algae blooms. 

Hyper-eutrophic lakes are very high in nutrients, and often exhibit large algae blooms, which may include dangerous levels of blue-green algae. Fish communities in hyper-eutrophic lakes are dominated by carp and other species that can tolerate warm temperatures and low oxygen conditions. Most hypereutrophic lakes are small impoundments of streams and fed by large watersheds composed of urban and/or agricultural land uses. 

Currently, both Round and Little Round Lakes are in the oligotrophic category for Chlorophyll A and Secchi Disk Depth (clarity). However, both lakes fall into the mesotrophic category for Total Phosphorus. LCO Environmental Specialist Brett McConnell stated that what worries him is the increase in phosphorus levels. There is an upward trend over the 2000 to 2023 period for Phosphorus in both lakes. Given the trend upwards in Total Phosphorus, it is a goal for RLPOA to work with property owners to reduce the amount of Phosphorus entering both of our lakes. 

McConnell stated the increase in Total Phosphorus is likely a direct reflection of all of the new construction and increases in impervious surfaces along with a loss of shoreline buffers. Excessive concentration of phosphorus is the most common cause of shoreline entrophication in lakes of the north. When you get a handle on the nutrients the ChlorA and Secchi disk readings will improve.

McConnell said he can’t stress enough the importance of buffering the shoreline to reduce nutrients, chemicals and sediment entering our lakes. 

RLPOA and the DNR strongly endorse the use of Healthy Lakes Best Practice projects to reduce run off into our lakes and also support leaving shorelines in a natural state or planting a buffer of native plants that can prevent/reduce nutrients, chemicals, and sediment from entering our lakes. RLPOA is a sponsor for the Healthy Lakes Best Practices grants of up to $1,000 per project. Contact Joan Buehrle at or at 608-788-6585 if you would like to learn more about the Best Practices grants or are interested in applying for one. We need to work together to preserve and protect our lakes. 

Note: 2007 was a year with extremely low water.