What is the water quality grade for Harmony Lake?

Harmony Lake in Mercer County, North Dakota received a water quality grade of C (Fair). Water clarity: 2.3 ft visibility. Chlorophyll-a (algae): 8.4 µg/L. Maximum depth: 21.2 ft. Surface area: 44.9 acres.

Is Harmony Lake safe to swim in?

Generally safe for swimming, moderate water quality. Harmony Lake has an overall water quality grade of C. Algae concentration (chlorophyll-a) is 8.4 µg/L. Always check local health department advisories before swimming.

How deep is Harmony Lake?

Harmony Lake has a maximum depth of 21.2 feet and an average depth of 10 feet. The lake covers 44.9 acres.

What fish are in Harmony Lake?

Fish species found in Harmony Lake include Bluegill, Rainbow Trout, Black Crappie, Northern Pike. Harmony Lake is located in Mercer County, North Dakota.

Mercer County, North Dakota

Harmony Lake

Grade CFair · 2.3 ft clarity

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Eutrophic

Harmony Lake is a 45-acre productive, nutrient-rich eutrophic lake in Mercer County, North Dakota with a maximum depth of 21 feet (10-foot average). Water quality is graded C based on 2 sampling years through 2023. The lake supports 4 documented fish species including Bluegill, Rainbow Trout, and Black Crappie. Public access is available with 1 public boat landing. Compared to the 4 other monitored lakes in Mercer County, Harmony Lake ranks #5 for water quality.

Source: EPA Water Quality Portal sampling records, North Dakota DNR, last sampled 2023-10-17. Grade methodology: LakeGrade methodology.

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Swimming Safety

Generally safe for swimming, moderate water quality

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Water Quality Grade: C, Fair

Very murky, less than 2.3 ft of visibility. Chlorophyll-a: 8.4 µg/L. Trophic State Index: 58.

Metric	Value	Grade
Water Clarity (Secchi Depth)	2.3 ft	F
Phosphorus	No data
Chlorophyll-a (Algae)	8.4 µg/L	B
Trophic State Index (TSI)	58	Eutrophic

High nutrients, frequent algae, reduced clarity

Lake Details

Characteristic	Value
Maximum Depth	21.2 ft
Average Depth	10 ft
Surface Area	45 acres
Shoreline Length	3.1 mi
Public Access	Yes

Where to stay near Harmony Lake

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Fish Species

Bluegill Rainbow Trout Black Crappie Northern Pike

Click a species to see every graded lake where it is documented.

Fishing Harmony Lake

Recreation & Access

Boat Landings

Yes

Public Access

Water Temperature

Harmony Lake averages about 61°F at the surface in summer, usually warmest in Jun (about 66°F) and coldest in Oct (about 49°F). These are typical values by month — not a live reading.

Jan

—

Feb

—

Mar

—

Apr

—

May

51°

Jun

66°

Jul

55°

Aug

61°

Sep

—

Oct

49°

Nov

—

Dec

—

Typical surface water temperature by month, from 18 field readings (2023–2023) via the EPA Water Quality Portal. See the full Harmony Lake water temperature breakdown →

Location

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County Ranking

Ranked #5 of 5 lakes in Mercer County

Cleaner Lakes Within 30 Miles

Harmony Lake holds Grade C. 5 nearby lakes hold higher grades.

See full comparison →

Nearby Lakes in Mercer County

Explore Harmony Lake across LakeGrade

North Dakota Fishing Guide

Fish species and top-graded lakes across North Dakota

Mercer County Fishing

Fish species and best lakes in Mercer County

Lake Fishing Forecast

Species activity outlook by water temperature and season

North Dakota Lake Trips

Where to stay at North Dakota's top lakes, each with its grade

Eutrophic Lakes

High nutrients, frequent algae, reduced clarity

The State of North Dakota's Lakes

North Dakota's cleanest and most-polluted lakes, ranked

More North Dakota Lake Rankings

Cleanest lakes in North Dakota

Top 25 by overall water quality score

Clearest lakes in North Dakota

Top 25 by Secchi water clarity

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Grade A/B + low algae filter

Family fishing lakes in North Dakota

Panfish-rich, public access

All North Dakota lakes

Full state directory

Other Grade C Lakes in North Dakota

Custer Mine Pond

McLean County · Clarity: 2.2 ft

East Arroda Lake

Oliver County · Clarity: 5.6 ft

Hiddenwood Lake

Ward County · Clarity: 3.1 ft

Lake Tschida

Grant County · Clarity: 2.4 ft

Lake Tschida

Grant County · Clarity: 5.1 ft

Lake Tschida

Grant County · Clarity: 6 ft

Eutrophic Lakes in North Dakota

Custer Mine Pond East Arroda Lake Hiddenwood Lake Lake Audubon

More records, surveys & data sources

Reservoir Info (USACE NID)

Harmony Lake is a man-made reservoir impounded by the Harmony Lake (completed 1998), built primarily for recreation on the East Antelope Creek; earth-type dam, 32 ft tall.

Surface area: 44.9 ac
Normal storage: 496.3 ac-ft
Max storage: 1,290 ac-ft
Drainage area: 14.8 sq mi
Hazard class: Low
Owner: ND Game & Fish

All listed purposes: Recreation;Fish and Wildlife Pond.

Source: USACE National Inventory of Dams, NID ID ND00871 · Operator website

Data Sources

Water quality data from the EPA Water Quality Portal

Grading methodology based on Metropolitan Council standards

Depth, fish, and access data from North Dakota Game & Fish

Public boat-access points from the USGS National Boat Ramps inventory

Most recent sample: 2023-10-17

Monitoring stations: 3

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