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LakeQuality

Cleaner Lakes Than South Lake

5 higher-graded lakes within 30 miles, ranked by grade improvement and proximity.

South Lake carries a Grade C (Fair) water quality score. Within 30 miles, 5 lakes hold a higher grade. Gananoque Lake (Leeds and Grenville Counties County, Grade A, 5.2 mi away) is the closest meaningful upgrade.

Reviewed by LakeQuality Editorial Team · Updated
1
A

Gananoque Lake

Leeds and Grenville Counties County, Ontario · 5.2 mi from South Lake
  • +Two grade letters higher (C → A)
  • ++5.6 ft water clarity
  • +Lower phosphorus (19.5 vs 26.1 µg/L)
2
A

Whitefish Lake

Leeds and Grenville Counties County, Ontario · 5.6 mi from South Lake
  • +Two grade letters higher (C → A)
  • ++7.2 ft water clarity
  • +Lower phosphorus (14.7 vs 26.1 µg/L)
3
A

Gananoque River Lake

Leeds and Grenville Counties County, Ontario · 6 mi from South Lake
  • +Two grade letters higher (C → A)
  • ++5.6 ft water clarity
  • +Lower phosphorus (17.5 vs 26.1 µg/L)
4
A

Grippen Lake

Leeds and Grenville Counties County, Ontario · 6 mi from South Lake
  • +Two grade letters higher (C → A)
  • ++8.2 ft water clarity
  • +Lower phosphorus (11.8 vs 26.1 µg/L)
5
B

Cranberry Lake

Frontenac County, Ontario · 3.6 mi from South Lake
  • +Higher grade (C → B)
  • ++4 ft water clarity
  • +Lower phosphorus (18.5 vs 26.1 µg/L)

Reading the cohort

5 cleaner lakes sit within 30 miles of South Lake in the EPA water-quality dataset. With that many higher-grade neighbors close by, South Lake's Grade C reflects something specific to the lake itself — not a regional water-quality ceiling. The neighbor list below isn't a small set of marginal upgrades; it's a real cohort of meaningfully cleaner choices for the same Ontario weekend.

Gananoque Lake (Leeds and Grenville Counties County, Grade A) is the closest cleaner option at 5.2 miles from South Lake — close enough to be a genuine substitute for most users, far enough that it isn't the same neighborhood lake. Worth the trip if water quality is the primary driver; less obvious if South Lake is on the way to other plans.

The EPA water-quality grading combines clarity (Secchi depth), phosphorus, and chlorophyll-a measurements from state environmental sampling. A higher letter grade reflects measurably cleaner water on those indicators, not subjective beauty or access quality — a Grade A lake might have worse boat-launch facilities or shoreline access than a Grade C neighbor, so the ranking is one input alongside the rest of trip planning. See the methodology page for the full grading formula.

How this list is built

Every lake on LakeQuality has a calculated grade from EPA Water Quality Portal samples — secchi depth, total phosphorus, and chlorophyll-a measured against Metropolitan Council thresholds. To suggest cleaner alternatives, we filter lakes within 30 miles to those with a strictly higher numeric score, then rank by grade improvement with a small proximity tiebreak. Cross-state and limited-data lakes are excluded so the list stays locally relevant.

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