Hillsborough County Lake Quality

New Hampshire, 37 lakes, average grade C (Fair)

Hillsborough County's 37 graded lakes fall in the moderate-density bracket for New Hampshire. 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. The county average is C — the middle of the rubric, with one or two lakes pulling the average up or down depending on year.

The county's lakes lean shallow, which makes the grades sensitive to wind, sediment-resuspension, and any nutrient inputs from the watershed. The cleanest lake on the books is Deering Reservoir-Deep Spot (A); the most-stressed is Darrah Pond-Deep Spot (D).

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Quick Answers for Hillsborough County

Cleanest lakes in Hillsborough County →Cleanest lakes in New Hampshire →Safest swimming lakes in New Hampshire →

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

All Lakes in Hillsborough County

37 lakes · 33 graded, 4 not rated33 graded lakes · 4 not rated, hidden

Include not-rated lakes (4)

#	Lake	Grade	Clarity	Phosphorus	Algae	Trophic	Access
1	ADeering Reservoir-Deep SpotHillsborough	A	No recent samples	9.6 µg/L	3 µg/L	No recent samples	Not recorded
2	AGregg Lake-Deep SpotHillsborough	A	No recent samples	9.9 µg/L	3.9 µg/L	No recent samples	Not recorded
3	ANubanusit Lake-Deep SpotHillsborough	A	No recent samples	5 µg/L	1.3 µg/L	No recent samples	Not recorded
4	APleasant Pond-Deep SpotHillsborough	A	No recent samples	12.6 µg/L	4.3 µg/L	No recent samples	Not recorded
5	BContention Pond-Deep SpotHillsborough	B	No recent samples	12 µg/L	8.5 µg/L	No recent samples	Not recorded
6	BDeering Lake-Morrotta BayHillsborough	B	No recent samples	9.5 µg/L	No recent samples	No recent samples	Not recorded
7	BNubanusit Lake-Hancock LandingHillsborough	B	No recent samples	5 µg/L	No recent samples	No recent samples	Not recorded
8	BPleasant Pond-Dam OutletHillsborough	B	No recent samples	10.1 µg/L	No recent samples	No recent samples	Not recorded
9	BPratt Pond-Deep SpotHillsborough	B	No recent samples	10.7 µg/L	8.2 µg/L	No recent samples	Not recorded
10	BPratt Pond-West ShoreHillsborough	B	No recent samples	7.6 µg/L	No recent samples	No recent samples	Not recorded
11	BRocky Pond-VlapHillsborough	B	No recent samples	10.5 µg/L	4.4 µg/L	No recent samples	Not recorded
12	BSilver Lake-Deep SpotHillsborough	B	No recent samples	11.4 µg/L	No recent samples	No recent samples	Not recorded
13	BWeare Reservoir-Collins LandingHillsborough	B	No recent samples	8.1 µg/L	No recent samples	No recent samples	Not recorded
14	BWeare Reservoir-Cottage Rd BrookHillsborough	B	No recent samples	11.4 µg/L	No recent samples	No recent samples	Not recorded
15	BWeare Reservoir-DamHillsborough	B	No recent samples	10.3 µg/L	No recent samples	No recent samples	Not recorded
16	BWeare Reservoir-Deep SpotHillsborough	B	No recent samples	14.1 µg/L	No recent samples	No recent samples	Not recorded
17	CCrystal Lake-Deep SpotHillsborough	C	No recent samples	16.9 µg/L	2.8 µg/L	No recent samples	Not recorded
18	CFranklin Pierce Lake-Deep SpotHillsborough	C	No recent samples	10.5 µg/L	6.2 µg/L	No recent samples	Not recorded
19	CGregg Lake-Hattie Brown BrookHillsborough	C	No recent samples	19 µg/L	No recent samples	No recent samples	Not recorded
20	CHaunted Lake-Deep SpotHillsborough	C	No recent samples	18.7 µg/L	8.6 µg/L	No recent samples	Not recorded
21	CLong Pond-NhHillsborough	C	No recent samples	24.2 µg/L	14.1 µg/L	No recent samples	Not recorded
22	CNorway Pond-Deep SpotHillsborough	C	No recent samples	12.1 µg/L	5.1 µg/L	No recent samples	Not recorded
23	CNutt Pond-Deep SpotHillsborough	C	No recent samples	26.8 µg/L	7.4 µg/L	No recent samples	Not recorded
24	COtternick Pond-Deep SpotHillsborough	C	No recent samples	23.7 µg/L	7.8 µg/L	No recent samples	Not recorded
25	CTobey Reservoir-Deep SpotHillsborough	C	No recent samples	16.1 µg/L	No recent samples	No recent samples	Not recorded
26	DDarrah Pond-Deep SpotHillsborough	D	No recent samples	158.9 µg/L	No recent samples	No recent samples	Not recorded
27	DDorrs Pond-Deep SpotHillsborough	D	No recent samples	27.7 µg/L	13.3 µg/L	No recent samples	Not recorded
28	DLincoln Pond-Deep SpotHillsborough	D	No recent samples	34.4 µg/L	No recent samples	No recent samples	Not recorded
29	DLovewell Pond-Deep SpotHillsborough	D	No recent samples	35.8 µg/L	No recent samples	No recent samples	Not recorded
30	DPleasant Pond-Public LandingHillsborough	D	No recent samples	419 µg/L	No recent samples	No recent samples	Not recorded
31	DRobinson Pond-Deep SpotHillsborough	D	No recent samples	37 µg/L	13.6 µg/L	No recent samples	Not recorded
32	DSebbins Pond-Deep SpotHillsborough	D	No recent samples	36.5 µg/L	3.5 µg/L	No recent samples	Not recorded
33	DStevens Pond-Deep SpotHillsborough	D	No recent samples	26.2 µg/L	11.8 µg/L	No recent samples	Not recorded
	NRDeering Lake-Campbell BayHillsborough	NR	No recent samples	7.1 µg/L	No recent samples	No recent samples	Not recorded
	NRDeering Lake-Zowski CoveHillsborough	NR	No recent samples	7.4 µg/L	No recent samples	No recent samples	Not recorded
	NRNoone Falls Mill Dam LakeHillsborough	NR	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	NRNubanusit Lake-Daloz CoveHillsborough	NR	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded

NR = not rated: the monitoring record does not meet the evidence bar for a grade. That is EPA Integrated Reporting Category 3 (insufficient information), not a failing grade. How grading works.

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Other Counties in New Hampshire

Carroll County

22 lakes · Avg grade B

Sullivan County

25 lakes · Avg grade B

Grafton County

35 lakes · Avg grade B

Strafford County

16 lakes · Avg grade B

Coos County

15 lakes · Avg grade B

Cheshire County

39 lakes · Avg grade B

See how Hillsborough County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all 49 states and 2 Canadian provinces.

Source: EPA National Aquatic Resource Surveys, 2026.