Cleaner Lakes Than Diamond Lake
2 lakes with lower nutrient and algae readings nearby, ranked by grade improvement and proximity.
Diamond Lake carries nutrient and algae readings on record. Within 30 miles, 2 lakes read lower. Harriet Lake (Hennepin County, Grade C) is the closest meaningful upgrade.
Reading the cohort
Only 2 lakes within a 30-mile radius read cleaner than Diamond Lake on nutrients and algae. The narrow set of options reflects either a fairly clean lake to begin with or a region without a wide range of cleaner alternatives, so the trip-planning decision is more constrained than the headline "cleaner lakes nearby" suggests.
The closest cleaner alternative, Harriet Lake in Hennepin County, sits miles from Diamond Lake. At that distance, the substitution cost is essentially zero: same drive time, same regional access, demonstrably cleaner water on the EPA indicators. For repeat visitors who care about clarity or phosphorus levels, swapping the routine to Harriet Lake is mostly a habit change rather than a logistics change.
Each lake's nutrient and algae readings — total phosphorus, total nitrogen, chlorophyll-a, and turbidity — are shown beside the EPA National Lakes Assessment 2022 condition class for that lake's own ecoregion, so a reading is compared against the lakes it would naturally resemble. LakeQuality publishes no letter grade. Lower readings mean measurably less nutrient and algae in the water, not better scenery or access: the lake with the clearest, lowest-nutrient water can have worse boat-launch facilities or shoreline access than a neighbor, so the comparison is one input alongside the rest of trip planning. How the readings are classified is on our methodology page.
How this list is built
Sampled lakes on LakeQuality carry readings from EPA Water Quality Portal samples — nutrients and algae measured against EPA National Lakes Assessment ecoregion classes. Secchi is shown, not scored. To suggest cleaner alternatives, we filter lakes within 30 miles to those with a strictly higher numeric score, then rank by the size of the improvement with a small proximity tiebreak. Cross-state and limited-data lakes are excluded so the list stays locally relevant.