Lake Monongalia spans 2,270 acres and reaches a maximum depth of 14 feet. Known for its recreational appeal and relatively clear water, the lake is currently classified as impaired due to mercury levels in fish tissue, making some fish unsafe for consumption. While the lake shows some traits of a eutrophic system, such as occasional nutrient fluctuations, it continues to support a generally healthy aquatic ecosystem.

However, a key concern is the presence of hydrogen sulfide, particularly in the Mill Pond area, where low oxygen levels lead to gas buildup under ice during winter. As the ice melts in spring, the release of hydrogen sulfide causes a strong rotten egg odor, and these concentrations exceed state water quality standards, indicating a need for focused management efforts.

Water quality trends show mixed results. Total Phosphorus (TP) is slightly declining and remains well below state thresholds. Total Suspended Solids (TSS) are gradually increasing, likely due to runoff and erosion, but still within acceptable limits. Chlorophyll-a (Chl-a) levels meet state standards, and Secchi depth readings reflect good water clarity and low turbidity.

While Lake Monongalia is currently in fair ecological condition, targeted improvements are necessary—particularly to address low oxygen conditions and hydrogen sulfide buildup. Continued water quality monitoring, sustainable land use practices, and community engagement will be key to improving the lake's health and ensuring it remains a valuable natural and recreational resource for future generations.

For more detailed water quality data, please follow the links below:

MPCA Surface Water Data

MN DNR Lake Finder