Patterns in Minnesota’s lake user perception, trophic state, and lake assessment datasets: a 35-year retrospective

Gamble A, Anderson J, Engel L. 2026. Patterns in Minnesota’s lake user perception, trophic state, and lake assessment datasets: a 35-year retrospective. Lake Reserv Manag. XXX–XXX. Formal lake user perception metrics were first developed in the United States (Vermont) in the 1980s and have been used by the Minnesota Pollution Control Agency (MPCA) professional and volunteer lake monitoring programs since 1987. We present the first comprehensive, state-wide analysis of this lake user perception data. Specifically, we analyzed patterns in paired lake user perception survey data and trophic state water quality datasets from 1987–2022. Both at the statewide and US Environmental Protection Agency Level III ecoregion scale, lake user perception metrics consistently agreed with the MPCA’s formal, science-based assessments of lake water quality and recreational use, despite numerous variations in field conditions, lake trophic status, and thousands of people (primarily volunteers) collecting the data. We found statistically significant differences in lake physical appearance and recreational suitability scores across gradients of total phosphorus and chlorophyll a concentrations and Secchi disk transparency. Scores were also significantly different between lakes formally assessed as impaired versus fully supporting aquatic recreation based on MPCA’s standards. Impaired waters had lower mean user perception scores than full support waters. Additionally, lake surveyors in regions with very low concentrations of chlorophyll a had a lower tolerance for lake algae than lake users in regions with higher concentrations of chlorophyll a. Similar patterns were true for Secchi disk transparency. We found that lake users were consistently successful at visually matching their judgments of lake water quality to the MPCA’s formal, science-based assessments of lake water quality, irrespective of geography.