Late afternoon sun over Slim Lake, scattering a bright path across wind-textured water

Sullivan County Lake Quality

New Hampshire, 39 lakes, measured by NHDES

The county-level average smooths over real differences — a single agricultural watershed near the southwest corner can pull the average down even if the rest of the county runs clean. 18 of those lakes carry recent nutrient and algae readings. The county-level summary describes that subset, not every water body listed. Most monitored lakes in Sullivan County carry favourable nutrient and algae readings for New Hampshire.

The county's lakes lean shallow, which makes the readings sensitive to wind, sediment-resuspension, and any nutrient inputs from the watershed. The cleanest measured lake is Ashuelot Pond-Deep Spot.

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Quick Answers for Sullivan County

Cleanest lakes in Sullivan County →Best swimming lakes in New Hampshire →

Planning a trip? Check special fishing regulations for Ashuelot Pond-Deep Spot — or check the official New Hampshire fishing regulations.

All Lakes in Sullivan County

39 lakes · 18 ranked on readings, 21 without enough sampling18 lakes ranked on readings · 21 without enough sampling, hidden

Include not-rated lakes (21)

#	Lake	Clarity	Phosphorus	Algae	Trophic	Max Depth	Access
1	Ashuelot Pond-Deep SpotSullivan	No recent samples	12.4 µg/L	3.9 µg/L	No recent samples	No recent samples	✓ Public
2	Crescent Lake-Deep SpotSullivan	No recent samples	10.2 µg/L	3.6 µg/L	No recent samples	No recent samples	✓ Public
3	Eastman Pond-Deep SpotSullivan	No recent samples	7.6 µg/L	3 µg/L	No recent samples	No recent samples	✓ Public
4	Ledge Pond-Deep SpotSullivan	No recent samples	7.6 µg/L	2.5 µg/L	No recent samples	No recent samples	Not recorded
5	Millen Pond-Deep SpotSullivan	No recent samples	8.1 µg/L	3.1 µg/L	No recent samples	No recent samples	✓ Public
6	Mountainview Lake-Deep SpotSullivan	No recent samples	10.9 µg/L	3 µg/L	No recent samples	No recent samples	✓ Public
7	Otter Pond-Deep SpotSullivan	No recent samples	9.8 µg/L	2.5 µg/L	No recent samples	No recent samples	✓ Public
8	Rand Pond-Deep SpotSullivan	No recent samples	9.4 µg/L	2.3 µg/L	No recent samples	No recent samples	✓ Public
9	Rockybound Pond-Deep SpotSullivan	No recent samples	12.2 µg/L	2.1 µg/L	No recent samples	No recent samples	Not recorded
10	Sunapee LakeSullivan	No recent samples	5 µg/L	1.1 µg/L	No recent samples	No recent samples	✓ Public
11	Black River Confluence LakeSullivan	No recent samples	14.2 µg/L	No recent samples	No recent samples	No recent samples	✓ Public
12	Dutchman Pond-Deep SpotSullivan	No recent samples	9.2 µg/L	1.8 µg/L	No recent samples	No recent samples	Not recorded
13	Long Pond-Deep SpotSullivan	No recent samples	6.6 µg/L	2.2 µg/L	No recent samples	No recent samples	✓ Public
14	Marshall Pond-Deep SpotSullivan	No recent samples	11.4 µg/L	No recent samples	No recent samples	No recent samples	Not recorded
15	Stocker Pond-Deep SpotSullivan	No recent samples	10 µg/L	0.8 µg/L	No recent samples	No recent samples	Not recorded
16	Baptist Pond-Deep SpotSullivan	No recent samples	14.2 µg/L	9.4 µg/L	No recent samples	No recent samples	Not recorded
17	Mill PondSullivan	No recent samples	28.9 µg/L	4 µg/L	No recent samples	No recent samples	Not recorded
18	Perkins Pond-Deep SpotSullivan	No recent samples	9.9 µg/L	14 µg/L	No recent samples	No recent samples	✓ Public
	Butterfield PondSullivan	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	✓ Public
	Butternut PondSullivan	No recent samples	No recent samples	No recent samples	No recent samples	10 ft	Not recorded
	Dutchman Pond-Hull-SchulmanSullivan	No recent samples	13.1 µg/L	No recent samples	No recent samples	No recent samples	Not recorded
	Gilman Pond-Deep SpotSullivan	No recent samples	5 µg/L	0.6 µg/L	No recent samples	No recent samples	Not recorded
	Governors PondSullivan	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Halfmoon Pond-Deep SpotSullivan	No recent samples	14.6 µg/L	No recent samples	No recent samples	No recent samples	✓ Public
	Kolelemook LakeSullivan	19.8 ft	No recent samples	No recent samples	No recent samples	No recent samples	✓ Public
	Lake ConistonSullivan	No recent samples	No recent samples	No recent samples	No recent samples	20 ft	✓ Public
	Lake SunapeeSullivan	26.7 ft	No recent samples	No recent samples	No recent samples	No recent samples	✓ Public
	May PondSullivan	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Miller PondSullivan	No recent samples	No recent samples	No recent samples	No recent samples	7.2 ft	Not recorded
	Mitchell PondSullivan	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Morgan PondSullivan	No recent samples	No recent samples	No recent samples	No recent samples	30 ft	Not recorded
	Moses Pond-Deep SpotSullivan	No recent samples	16.9 µg/L	No recent samples	No recent samples	No recent samples	Not recorded
	North PondSullivan	No recent samples	No recent samples	No recent samples	No recent samples	10 ft	Not recorded
	Perkins Pond-BurmaSullivan	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Red Leaf PondSullivan	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Smith PondSullivan	No recent samples	No recent samples	No recent samples	No recent samples	30 ft	✓ Public
	Spectacle PondSullivan	No recent samples	No recent samples	No recent samples	No recent samples	24.9 ft	Not recorded
	Star LakeSullivan	No recent samples	No recent samples	No recent samples	No recent samples	61 ft	Not recorded
	The OverflowSullivan	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded

NR = no nutrient or algae reading on record. The measurements are published as the authority reports them. Where the data comes from.

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Source: the New Hampshire Department of Environmental Services. See data sources.