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

Merrimack County Lake Quality

New Hampshire, 90 lakes, measured by NHDES

Merrimack County in New Hampshire carries 90 monitored lakes — one of the lake-richer counties in our dataset. Coverage that dense usually reflects active lake-association sampling alongside state-agency monitoring. 36 of those lakes carry recent nutrient and algae readings. The county-level summary describes that subset, not every water body listed. The county-wide picture is low-to-moderate phosphorus with clear summer transparency across most monitored lakes.

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 Blaisdell Lake-Deep Spot.

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

All Lakes in Merrimack County

90 lakes · 36 ranked on readings, 54 without enough sampling36 lakes ranked on readings · 54 without enough sampling, hidden

Include not-rated lakes (54)

#	Lake	Clarity	Phosphorus	Algae	Trophic	Max Depth	Access
1	Blaisdell Lake-Deep SpotMerrimack	No recent samples	8.2 µg/L	2.8 µg/L	No recent samples	No recent samples	✓ Public
2	Clough Pond-Deep SpotMerrimack	No recent samples	15.8 µg/L	3.5 µg/L	No recent samples	No recent samples	✓ Public
3	Cold Pond-Deep SpotMerrimack	No recent samples	8.6 µg/L	0.8 µg/L	No recent samples	No recent samples	Not recorded
4	Highland Lake-Deep SpotMerrimack	No recent samples	13.1 µg/L	3.5 µg/L	No recent samples	No recent samples	Not recorded
5	Lake Massasecum-Deep SpotMerrimack	No recent samples	9.6 µg/L	3.2 µg/L	No recent samples	No recent samples	✓ Public
6	Lake Winnepocket-Deep SpotMerrimack	No recent samples	8.1 µg/L	3.2 µg/L	No recent samples	No recent samples	Not recorded
7	Bear Hill Pond-Deep SpotMerrimack	No recent samples	7.4 µg/L	No recent samples	No recent samples	No recent samples	Not recorded
8	Bradley Lake-Deep SpotMerrimack	No recent samples	5.6 µg/L	No recent samples	No recent samples	No recent samples	Not recorded
9	Chalk Pond-Main BeachMerrimack	No recent samples	5.7 µg/L	No recent samples	No recent samples	No recent samples	✓ Public
10	Chase Pond-Deep SpotMerrimack	No recent samples	12.6 µg/L	4.2 µg/L	No recent samples	No recent samples	Not recorded
11	Chestnut Pond-Deep SpotMerrimack	No recent samples	10 µg/L	4.3 µg/L	No recent samples	No recent samples	✓ Public
12	Knowles Pond-Deep SpotMerrimack	No recent samples	8 µg/L	2.8 µg/L	No recent samples	No recent samples	✓ Public
13	Lake Winnepocket-Austin PointMerrimack	No recent samples	5.2 µg/L	No recent samples	No recent samples	No recent samples	Not recorded
14	Lake Winnepocket-CogswellMerrimack	No recent samples	6.1 µg/L	No recent samples	No recent samples	No recent samples	Not recorded
15	Lake Winnepocket-Dawe PointMerrimack	No recent samples	5.5 µg/L	No recent samples	No recent samples	No recent samples	Not recorded
16	Lake Winnepocket-Pratt CoveMerrimack	No recent samples	5.6 µg/L	No recent samples	No recent samples	No recent samples	Not recorded
17	Lake Winnepocket-West Wind VillageMerrimack	No recent samples	6.1 µg/L	No recent samples	No recent samples	No recent samples	Not recorded
18	Pillsbury Lake-Deep SpotMerrimack	No recent samples	13.8 µg/L	No recent samples	No recent samples	No recent samples	✓ Public
19	Pleasant Lake-OutletMerrimack	No recent samples	5 µg/L	No recent samples	No recent samples	No recent samples	✓ Public
20	Pleasant Lake-Southeast CoveMerrimack	No recent samples	5 µg/L	No recent samples	No recent samples	No recent samples	Not recorded
21	Waukeena Lake-Deep SpotMerrimack	No recent samples	10 µg/L	3.5 µg/L	No recent samples	No recent samples	✓ Public
22	Chalk Pond-Deep SpotMerrimack	No recent samples	9.7 µg/L	4.9 µg/L	No recent samples	No recent samples	Not recorded
23	Clement Pond-Deep SpotMerrimack	No recent samples	11.1 µg/L	5.1 µg/L	No recent samples	No recent samples	✓ Public
24	Highland Lake-OutletMerrimack	No recent samples	16.6 µg/L	No recent samples	No recent samples	No recent samples	Not recorded
25	Hothole Pond-Deep SpotMerrimack	No recent samples	16.4 µg/L	5.9 µg/L	No recent samples	No recent samples	✓ Public
26	Kezar Lake-Deep SpotMerrimack	No recent samples	22.6 µg/L	3.4 µg/L	No recent samples	No recent samples	✓ Public
27	Lyford Pond-Deep SpotMerrimack	No recent samples	18 µg/L	No recent samples	No recent samples	No recent samples	Not recorded
28	Messer Pond-Deep SpotMerrimack	No recent samples	16.8 µg/L	3.6 µg/L	No recent samples	No recent samples	Not recorded
29	New Pond-Deep SpotMerrimack	No recent samples	14.4 µg/L	4.7 µg/L	No recent samples	No recent samples	Not recorded
30	Russell Pond-Deep SpotMerrimack	No recent samples	19.1 µg/L	No recent samples	No recent samples	No recent samples	Not recorded
31	Sucker Brook LakeMerrimack	No recent samples	18.6 µg/L	No recent samples	No recent samples	No recent samples	✓ Public
32	Todd Lake-Deep SpotMerrimack	No recent samples	15.8 µg/L	4.7 µg/L	No recent samples	No recent samples	Not recorded
33	Tom Pond-Deep SpotMerrimack	No recent samples	13.1 µg/L	7.8 µg/L	No recent samples	No recent samples	Not recorded
34	Turee Pond-Deep SpotMerrimack	No recent samples	19.5 µg/L	4.3 µg/L	No recent samples	No recent samples	✓ Public
35	Turee Pond-Firehouse Pond OutletMerrimack	No recent samples	18.2 µg/L	No recent samples	No recent samples	No recent samples	Not recorded
36	Webster Lake-Deep SpotMerrimack	No recent samples	17.6 µg/L	3.3 µg/L	No recent samples	No recent samples	✓ Public
	Adder PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	15 ft	Not recorded
	Bagley PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	10 ft	Not recorded
	Bear PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	43 ft	Not recorded
	Berry PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	20.7 ft	Not recorded
	Billings PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	15 ft	Not recorded
	Bog PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	5 ft	Not recorded
	Chalk Pond-South BeachMerrimack	No recent samples	7.5 µg/L	No recent samples	No recent samples	No recent samples	Not recorded
	Clark PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	14.1 ft	Not recorded
	Clay PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	18 ft	Not recorded
	Cole Pond-BeachMerrimack	No recent samples	9.9 µg/L	No recent samples	No recent samples	No recent samples	Not recorded
	Crane Neck PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Craney Pond-Deep SpotMerrimack	No recent samples	16.3 µg/L	6.5 µg/L	No recent samples	No recent samples	✓ Public
	Crooked PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	20 ft	Not recorded
	Drew LakeMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	7.2 ft	✓ Public
	Dubes PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	5 ft	Not recorded
	Eagle PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	22 ft	Not recorded
	Elbow PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	20 ft	Not recorded
	Flaghole PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	18 ft	Not recorded
	French PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	40 ft	✓ Public
	Gile PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	5 ft	Not recorded
	Giles Pond-Deep SpotMerrimack	No recent samples	13.4 µg/L	5.2 µg/L	No recent samples	No recent samples	✓ Public
	Gorham PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	15 ft	✓ Public
	Grassy PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	20 ft	Not recorded
	Heads PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	10 ft	Not recorded
	Hoit Road MarshMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Hopkinton LakeMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	9 ft	✓ Public
	Horseshoe PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	10 ft	Not recorded
	Kimball PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	15 ft	✓ Public
	Knights Meadow Marsh ReservoirMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Lake Massasecum-GenericMerrimack	No recent samples	9 µg/L	No recent samples	No recent samples	No recent samples	Not recorded
	Lake Winnepocket-Agoos ShoreMerrimack	No recent samples	6.3 µg/L	No recent samples	No recent samples	No recent samples	Not recorded
	Lake Winnepocket-End of Lake InletMerrimack	No recent samples	7.7 µg/L	No recent samples	No recent samples	No recent samples	Not recorded
	Little Turkey PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Loch LyndonMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Long PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	15 ft	Not recorded
	Morrill PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Palmer PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Penacook LakeMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	64 ft	Not recorded
	Piper PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	15 ft	Not recorded
	Pleasant PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	30 ft	✓ Public
	Putney Meadow PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Rocky PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	35 ft	Not recorded
	Rolf Pond-Deep SpotMerrimack	No recent samples	12.3 µg/L	No recent samples	No recent samples	No recent samples	✓ Public
	Sanborn PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	20 ft	Not recorded
	School PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	20 ft	Not recorded
	Sondogardy PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	15 ft	Not recorded
	Suncook River LakeMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	✓ Public
	Trumbull PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	18 ft	Not recorded
	Tucker PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Turkey PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	5 ft	Not recorded
	Turtle PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	15 ft	Not recorded
	Upper PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	20 ft	✓ Public
	Walker PondMerrimack	10.4 ft	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Whites PondMerrimack	No recent samples	No recent samples	No recent samples	No recent samples	9.8 ft	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.