Lake Washington Water Quality Management Plan

ISG partnered with the Lake Washington Improvement Association (LWIA), in close collaboration with the Le Sueur Soil and Water Conservation District (SWCD), to identify Lake Washington’s primary causes of water quality degradation. ISG and the LWIA synthesized lake and watershed data, previous studies, and Total Maximum Daily Load (TMDL)/Watershed Restoration and Protection Strategies (WRAPS) results for the Middle Minnesota River Watershed. ISG then developed a water quality improvement implementation plan, establishing targets for nutrient reduction, habitat improvement, and long-term watershed management.

Based on the implementation plan, an ISG monitoring program launched in 2021 to track multiple in-lake stations, tributary inlets, and the Shanaska Creek outlet. Surface and bottom samples are evaluated for nutrient conditions, while continuous flow and water-level data provide insight into watershed dynamics. Findings consistently have shown watershed inputs remain the dominant source of nutrient enrichment, with internal loading playing a comparatively minor role.

This expanding, multi-year dataset strengthens adaptive management by refining nutrient-response models, assessing BMP effectiveness, and guiding future restoration investments. By pairing our data collection measures with engineered solutions, ISG, LWIA, and the Le Sueur SWCD will continue to implement efficient, targeted strategies that advance long-term lake stewardship and measurable improvements in water quality.