Cleanest Lakes in Pennsylvania: Top 0 Ranked by Water Quality
Filtered to remove lakes with limited data (<3 sampling years). Sorted by overall water quality score.
Ranking the cleanest Pennsylvania lakes means picking the basins that score high on all three water-quality dimensions, not just one. a leading lake leads the list with a grade of —, with a runner-up close behind.
The top of the cleanest-lakes list is dominated by deep, glacial, cold-water basins — the same basins that produce the A-grade bracket overall. The pattern is not coincidence: depth and watershed land-use are the dominant inputs to water-clarity and nutrient-loading both.
| Rank | Lake | County | Grade | Clarity | Phosphorus | Chlorophyll-a | Area |
|---|
Clearest lakes in Pennsylvania by water clarity
“Clearest” ranks by Secchi depth — how far you can see into the water — which can differ from the combined cleanliness score above. The clearest water in Pennsylvania is Lake Carey at 5.9 ft of Secchi visibility.
- 1. Lake Carey — 5.9 ft, Wyoming County
- 2. Lake Wallenpaupack — 5.7 ft, Pike County
- 3. Lake Nockamixon — 4.8 ft, Bucks County
Frequently Asked Questions
What is the cleanest lake in Pennsylvania?
Lake quality is ranked here using a combined score of Secchi depth, phosphorus, and chlorophyll-a. The top-ranked lake on this page has the highest score in Pennsylvania for 2026.
What is the most polluted lake in Pennsylvania?
Pollution rankings are tracked separately on the most-polluted-lakes page. The lakes with the highest phosphorus and chlorophyll-a measurements typically have the lowest grades.
Where in Pennsylvania has the cleanest water?
Pennsylvania's clearest waters are concentrated in deeper, lower-nutrient glacial basins with forested or low-agriculture watersheds. Among the current top-ranked lakes above, the counties listed above produce the highest-scoring lakes.
What is the clearest lake in Pennsylvania?
Lake Carey is the clearest lake in Pennsylvania by water clarity, with a Secchi depth of 5.9 feet — the deepest transparency in our 2026 dataset. "Clearest" ranks by Secchi depth (how far you can see into the water) specifically, while "cleanest" combines clarity with phosphorus and chlorophyll-a. See our full clearest-lakes ranking for Pennsylvania for the top 25 by Secchi clarity.
Are these lakes safe to swim in?
A and B grade lakes are typically safe for swimming under normal conditions. Chlorophyll-a below 10 µg/L means low risk of harmful algal blooms. Always check posted advisories before swimming — water quality changes seasonally, especially in late summer when blue-green algae bloom risk peaks.
How are these grades calculated?
Each lake is scored on three signals: Secchi depth (water clarity in feet), total phosphorus (nutrient load in µg/L), and chlorophyll-a (algae concentration in µg/L). Each gets a 0–100 sub-score relative to Pennsylvania state norms. The three sub-scores average into the overall score, which maps to an A–F letter grade. Methodology details live on our methodology page.
What are the top 5 cleanest lakes in the US?
There is no single national ranking of cleanest lakes — each state agency uses different metrics. Crater Lake (Oregon) is widely cited as the clearest US lake, with Secchi depths over 30 m. Lake Tahoe and Lake Superior are also top-tier nationally. Within Pennsylvania, the lakes ranked above are the top 25 by our standardized 2026 grading.
How we rank cleanest lakes
Cleanliness here means three things working together:
- Secchi clarity — how deep you can see into the water (in feet). Greater depth = clearer water = lower suspended sediment and algae.
- Total phosphorus — the nutrient that fuels algae. Lower phosphorus levels mean less algae growth potential.
- Chlorophyll-a — the green pigment in algae. Direct measurement of how much algae is currently in the water.
Each signal is normalized against Pennsylvania state norms and combined into a single 0–100 score. The lakes above are sorted by that combined score.Full methodology →
Where to stay near Pennsylvania's cleanest lakes
Compare cabins, resorts, and rentals near the clearest, lowest-algae lakes in Pennsylvania — live availability and prices for your trip.
Top-rated places to stay near Pennsylvania's cleanest lakes
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Source: EPA National Aquatic Resource Surveys, 2026.