Protecting Long Lake's Water Quality
Long Lake volunteers have monitored water quality for decades, creating a valuable record of how conditions in the lake change over time. Secchi disk readings measuring water clarity have been reported to the Minnesota Pollution Control Agency (MPCA) since 1984.
Since 1997, the monitoring program has also included monthly testing from May through September for total phosphorus and chlorophyll-a. Samples are coordinated through the Hubbard County Coalition of Lake Associations (HCCOLA), analyzed by RMB Environmental Laboratories, and the results are uploaded annually to the MPCA database.
LLAA also works with the Hubbard County Soil & Water Conservation District (HCSWCD) to monitor dissolved oxygen and water temperature at Site 202, near the deepest point in Long Lake. Together, these measurements help track water-quality trends and conditions for fish and other aquatic life.
Long-term water quality monitoring is supported in part by donations to the LLAA Foundation.
Notable 2026 Water Clarity Reading
18.5 feet
Secchi depth recorded July 26, 2026
According to MPCA data cited in the LLAA newsletter, a Secchi depth of 18.5 feet had not been recorded on Long Lake since the mid-1990s.
How Water Quality Is Monitored
Each season the Long Lake water quality monitoring team collects samples monthly from May through September. Monitoring takes place at Long Lake Site 202 near the deepest part of the lake. Water samples are placed in designated bottles and sent to RMB Environmental Laboratories for analysis.
Water Clarity
Secchi disk readings have been reported to the MPCA since 1984.
Water Sampling
Monthly testing from May through September includes total phosphorus and chlorophyll-a.
Oxygen & Temperature
Measurements at Site 202, near the deepest point in Long Lake, help assess conditions for fish and other aquatic life.
Total Suspended Solids (TSS) are among the measurements used to track water quality. TSS consists of particles suspended in the water, including soil, organic material, and algae. Monitoring TSS helps track how runoff and shoreline erosion may affect water clarity and lake health.
Water Quality Reports
Water Quality Trends
2020 Long Lake Water Monitoring Trend Analysis (10-Year Review)
This report summarizes a decade of Long Lake water-quality data and trends using information from LLAA volunteers, RMB Environmental Laboratories, the Minnesota Pollution Control Agency, and other state data sources.
2021 Water Monitoring Results & Historical Trends
This report summarizes 2021 volunteer monitoring results for chlorophyll-a, total phosphorus, and Secchi water clarity, along with historical water-clarity and lake-level data.
Historical Studies
Long Lake Report: 20 Years in Depth
This report from RMB Environmental Laboratories contains water quality data through 2016.
Collected Data Conclusions and Strategies
This report from the Hubbard County Soil & Water Conservation District and RMB Environmental Laboratories examines Long Lake water-quality data collected from 1984 through 2011 and identifies conclusions and strategies based on those findings.
Dissolved Oxygen & Temperature Monitoring
Since 2012, Long Lake volunteers have worked with the Hubbard County Soil & Water Conservation District (HCSWCD) to monitor dissolved oxygen and water temperature at Site 202, near the lake’s deepest point. Volunteers take measurements meter by meter five times each summer to help assess habitat conditions for fish and other aquatic life.
Current dissolved oxygen and temperature reports are available on the Fish & Fisheries page.
Help Support Long Lake Water Monitoring
Help keep Long Lake’s long-term water quality monitoring program strong by volunteering, supporting the LLAA Foundation, or becoming an LLAA member.