Frontenac County Lake Quality

Ontario, 107 lakes, average grade A (Excellent)

Frontenac County in Ontario carries 107 graded lakes — one of the lake-richer counties in our dataset. Coverage that dense usually reflects active lake-association sampling alongside state-agency monitoring. The county's average grade is A — among the cleanest in Ontario. 84 lakes pull an A on their own, and almost none fall into the D or F brackets.

Most of the county's monitored lakes are shallow — under 50 feet — which means wind keeps the water column mixed all summer and sediment-bound phosphorus releases back into the surface layer whenever the bottom is disturbed. Ardoch Lake (A) is the cleanest in the county.

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Quick Answers for Frontenac County

Cleanest lakes in Frontenac County →Cleanest lakes in Ontario →Safest swimming lakes in Ontario →

Planning a trip? Check special fishing regulations for Ardoch Lake — or check the official Ontario fishing regulations.

All Lakes in Frontenac County

Rank	Lake	Grade	Clarity	Phosphorus
1	Ardoch Lake	A	19 ft	6.8 µg/L
2	Big Clear Lake	A	15.1 ft	9 µg/L
3	Big Clear Lake	A	21.3 ft	8.1 µg/L
4	Big Olhman Lake	A	16.4 ft	13.8 µg/L
5	Blue Lake	A	37.7 ft	8.1 µg/L
6	Bobs Lake	A	15.7 ft	9.3 µg/L
7	Brule Lake	A	23.3 ft	5.4 µg/L
8	Buckshot Lake	A	17.1 ft	5.8 µg/L
9	Burridge Lake	A	17.2 ft	9 µg/L
10	Canonto Lake	A	20 ft	6.2 µg/L
11	Crow Lake	A	17.4 ft	7 µg/L
12	Desert Lake	A	19 ft	9.1 µg/L
13	Devil Lake	A	21.3 ft	7.4 µg/L
14	Eagle Lake	A	17.9 ft	8.5 µg/L
15	Fortune Lake	A	27.9 ft	-
16	Fourteen Island Lake	A	21.3 ft	11.4 µg/L
17	Garter Lake	A	16.7 ft	-
18	Gould Lake	A	18 ft	6.7 µg/L
19	Green Lake	A	21.2 ft	5.2 µg/L
20	Grindstone Lake	A	18 ft	4.9 µg/L
21	Kashwakamak Lake	A	15.7 ft	7.2 µg/L
22	Leggat Lake	A	22.6 ft	-
23	Little Long Lake	A	14.9 ft	9.7 µg/L
24	Long Schooner Lake	A	20.2 ft	16.4 µg/L
25	Lower Rock Lake	A	16.1 ft	8.3 µg/L
26	Lucky Lake	A	21.3 ft	8.2 µg/L
27	Mackie Lake	A	19 ft	5.3 µg/L
28	Mazinaw Lake	A	16.1 ft	4.3 µg/L
29	Milk Lake	A	20.7 ft	11.6 µg/L
30	Mississagagon Lake	A	23 ft	6.3 µg/L
31	Mosque Lake	A	16.1 ft	6.4 µg/L
32	O'Reilly Lake	A	20 ft	-
33	Palmerston Lake	A	21.3 ft	4.8 µg/L
34	Pine Lake	A	16.4 ft	6.5 µg/L
35	Potspoon Lake	A	17.1 ft	11.3 µg/L
36	Round Schooner Lake	A	16.4 ft	8.7 µg/L
37	Sharbot Lake	A	17.1 ft	8.9 µg/L
38	Shawenegog Lake	A	15.4 ft	6.7 µg/L
39	Sigsworth Lake	A	16.4 ft	9.1 µg/L
40	Silver Lake	A	20 ft	6.3 µg/L
41	Sunday Lake	A	15.3 ft	8 µg/L
42	Sydenham Lake	A	15.7 ft	12.3 µg/L
43	Thirteen Island Lake	A	15.1 ft	12.5 µg/L
44	Thirty Island Lake	A	18.7 ft	10.5 µg/L
45	Wolfe Lake	A	20 ft	9.9 µg/L
46	Cranberry Lake	A	-	11.7 µg/L
47	Darling Lake	A	-	12.8 µg/L
48	Garrison Lake	A	-	10.2 µg/L
49	Horseshoe Lake	A	-	12 µg/L
50	Spring Lake	A	-	12.1 µg/L
51	Warrens Lake	A	-	10.9 µg/L
52	Black Lake	A	-	15.4 µg/L
53	Govan Lake	A	17.2 ft	15.6 µg/L
54	Big Gull Lake	A	13.1 ft	8.1 µg/L
55	Birch Lake	A	14.1 ft	8.8 µg/L
56	Buck Lake	A	13.1 ft	9.7 µg/L
57	Buckshot Lake	A	13.5 ft	5.1 µg/L
58	Butterill Lake	A	14.4 ft	14.1 µg/L
59	Canoe Lake	A	14.1 ft	7.9 µg/L
60	Carnahan Lake	A	10.5 ft	19 µg/L
61	Crotch Lake	A	13.1 ft	7.7 µg/L
62	Elbow Lake	A	10.8 ft	15.5 µg/L
63	Fermoy Lake	A	11.3 ft	13.5 µg/L
64	Fishing Lake	A	13.1 ft	10.1 µg/L
65	Guerley Lake	A	13.1 ft	14.5 µg/L
66	Hambly Lake	A	14.6 ft	10.2 µg/L
67	Howes Lake	A	12.8 ft	17.3 µg/L
68	Knowlton Lake	A	13.1 ft	8.2 µg/L
69	Long Lake	A	11.2 ft	15.2 µg/L
70	Loughborough Lake	A	13.1 ft	11.7 µg/L
71	Malcolm Lake	A	14.8 ft	9.4 µg/L
72	North Otter Lake	A	14.1 ft	10.3 µg/L
73	Opinicon Lake	A	13.1 ft	13.6 µg/L
74	Penyck Lake	A	11.5 ft	13 µg/L
75	St Andrew Lakes	A	11.8 ft	13.4 µg/L
76	Swaugers Lake	A	12.1 ft	9.3 µg/L
77	Turtle Lake	A	14.8 ft	11.1 µg/L
78	Upper Rock Lake	A	11.2 ft	12 µg/L
79	White Lake	A	11.5 ft	7.5 µg/L
80	Belmont Lake	A	10.5 ft	8.9 µg/L
81	Big Salmon Lake	A	13.1 ft	8.1 µg/L
82	Kishkebus Lake	A	10.5 ft	6.1 µg/L
83	Little John Lake	A	14.4 ft	19.2 µg/L
84	St Andrews Lake	A	11.5 ft	14.3 µg/L
85	Collins Lake	B	8.5 ft	18 µg/L
86	Cox'S Lake	B	7.5 ft	9.6 µg/L
87	Cranberry Lake	B	8.9 ft	18.5 µg/L
88	Crotch Lake	B	8.5 ft	10.5 µg/L
89	Elbow Lake	B	9.8 ft	14.8 µg/L
90	Fawn Lake	B	12.3 ft	-
91	Horseshoe Lake	B	9.8 ft	8.5 µg/L
92	Hungry Lake	B	7.9 ft	6.7 µg/L
93	Kennebec Lake	B	8.9 ft	9.6 µg/L
94	Mink Lake	B	9.2 ft	8.5 µg/L
95	Shabomeka Lake	B	14.4 ft	-
96	Big Gull Lake	B	8.9 ft	9 µg/L
97	Bull Lake	B	7.5 ft	10.1 µg/L
98	Fourth Depot Lake	B	7.2 ft	11.9 µg/L
99	Little Clear Lake	B	6.9 ft	16.6 µg/L
100	Buffy Lake	B	9.2 ft	21 µg/L
101	Cole Lake	B	5.9 ft	18.5 µg/L
102	Inverary Lake	B	5.9 ft	19.1 µg/L
103	Rock Lake	B	5.9 ft	12.6 µg/L
104	Unnamed Lake	B	7.7 ft	23.4 µg/L
105	Dog Lake	C	6.2 ft	28.1 µg/L
106	Pot Lake	C	3.6 ft	28.4 µg/L
107	Unnamed Lake	C	3.9 ft	35.2 µg/L