How Clean Is the Water on Simonton Lake in Elkhart, Indiana?

Simonton Lake, a roughly 300-acre recreational lake in Elkhart County, Indiana, is widely regarded as having better water quality than many other lakes across the state. While it is not a pristine wilderness lake, long-term monitoring shows it maintains moderate nutrient levels, relatively good clarity, and conditions suitable for boating, fishing, swimming, and other water activities when managed carefully.

A comprehensive Diagnostic/Feasibility Study completed in 2010 for the Simonton Lake Homeowners Association found that the lake’s overall water quality was “much better than most of Indiana’s lakes.” The study classified it as mesotrophic—meaning moderate productivity with balanced nutrients rather than the high-nutrient, algae-prone eutrophic condition common in many Midwestern lakes. Total phosphorus concentrations had declined steadily from a mean of 0.055 mg/L in 1988 to under 0.030 mg/L by 2010. Chlorophyll-a levels (an indicator of algal biomass) were low, and Secchi disk transparency readings ranged from about 6.2 to 8.5 feet during surveys.

The lake is strongly phosphorus-limited, so controlling phosphorus inputs is key to preventing excessive algae growth. Surface runoff into the lake is relatively limited, which helps keep external nutrient loading lower than in lakes with large agricultural or urban watersheds. However, local sources—such as fertilizer from lakeside lawns, pet waste, and sediment disturbance from heavy boat traffic—remain important management concerns. Deep portions of the west basin can become low in oxygen during summer stratification, a common trait in many stratified lakes.

More recent state data support a similar picture. In Indiana’s 2026 Integrated Water Monitoring and Assessment Report, Simonton Lake is listed as mesotrophic based on Carlson Trophic State Index scores (chlorophyll-a TSI of 49, with supporting phosphorus and Secchi values). Its trend is described as fluctuating. Clarity readings around 6–7 feet continue to appear in recent summaries, consistent with earlier findings.
Bacterial monitoring through the Greater Elkhart County Stormwater Partnership has shown Simonton Lake among the sites with lower E. coli levels compared with nearby streams and creeks, which is favorable for recreational contact. Blue-green algae (cyanobacteria) have been the dominant phytoplankton group in past sampling, though overall densities remained relatively low and did not trigger widespread nuisance conditions
 in the available reports.

Local stewardship plays a significant role. The Simonton Lake Conservancy and homeowners association monitor water quality, address drainage and vegetation issues, and support efforts such as weed management and shoreline practices that help protect the lake. Residents and visitors are encouraged to minimize fertilizer use near the water, properly dispose of waste, and operate boats responsibly to reduce sediment resuspension.

​In summary, Simonton Lake’s water is generally clean enough for typical recreational uses and ranks favorably against many Indiana lakes. It is not oligotrophic (ultra-clear and nutrient-poor), and ongoing vigilance against nutrient inputs is essential to maintain its current status. For the most current conditions—especially regarding algae or bacteria—check local HOA updates, Indiana Department of Environmental Management resources, or recent water testing results before swimming or allowing pets in the water. With continued community care, Simonton Lake can remain a valued recreational resource for Elkhart and surrounding areas.