Pleasant Lake, Long Lake & Plainfield Lake
The three study lakes are Pleasant Lake, Long Lake and Plainfield Lake, located in Waushara County within the Central Sands Region. All three study lakes are seepage lakes, meaning they have no streams or rivers flowing into or out of the lakes. The primary sources of water for the study lakes are precipitation and groundwater inflow.
As part of the state law, the DNR had to define “significant reduction…of the navigable lake’s …average seasonal water levels” for these lakes (s. 281.34(7m)(b), Wis. Stats). All of the study lakes experience variability in lake levels. Lake levels vary more between years than they do between months. The DNR defined average seasonal water level to mean the pattern of high, normal and low lake levels that naturally occur on the study lakes. DNR defined significant reduction to be a deviation from this natural pattern strong enough to cause a significant impact or change to the study lake ecosystems.
The DNR concluded the magnitude of lake level patterns are most important for these seepage lakes. The DNR determined how changing water levels can impact human uses (recreational opportunities), fish, aquatic plants and lake chemistry. One study finding is that groundwater withdrawals lower lake levels across the full range of water levels (high, low and median). DNR concluded significant reductions from current irrigated agriculture result in impacts to the ecosystems at Long Lake and Plainfield Lake. The DNR provides additional details in the Lake Resource Methodology Presentation, the Central Sands Lakes Study Report: Findings and Recommendations, Appendix B and Presentation.
Pleasant Lake is the largest of the three study lakes, with a maximum depth of 25 feet and a surface area of 120 acres. Pleasant Lake has many homes along the shoreline and is used for fishing, swimming, water skiing and boating. Pleasant Lake is mesotrophic. Mesotrophic lakes are characterized by moderate plant and algae growth, medium nutrient levels, and are fairly clear with submergent plants. Pleasant Lake is the only one of the study lakes that stratifies - meaning the lake forms a warm upper and cold lower layer. Stratification is important for water quality and aquatic organisms. Pleasant Lake also has hard water, good water clarity and a high-quality aquatic plant community. It supports a fishery consisting of bluegill, pumpkinseed, perch, largemouth bass and northern pike, in addition to other non-game and small fishes.
Long Lake is a 40-acre lake with maximum depths of 10-14 feet. Long Lake has many homes along the shoreline. Long Lake supports a stunted bluegill and bass fishery and is used for wildlife viewing, fishing, swimming and slow/no-wake boating. Long Lake is shallow, well-mixed and also mesotrophic. Long Lake occasionally experiences low dissolved oxygen levels, even though there are mechanical aerators in the lake to improve oxygen levels.
Plainfield Lake is a 29-acre lake with maximum depths of 11-12 feet. Plainfield Lake is within a State Natural Area and has a few homes on the shoreline. The lake is home to a rare, federally-protected plant and has high quality emergent wetlands. The lake only supports fish intermittently and is primarily used for wildlife viewing, birdwatching and waterfowl hunting. Plainfield Lake is a shallow, well-mixed, oligotrophic lake. Oligotrophic lakes are typically clear, due to the low algae, productivity and nutrient levels in the lakes. Plainfield Lake has hard water (high alkalinity, calcium and magnesium concentrations).