Harmony Lake
Mercer County, North Dakota45 acresView mapDirections
Nutrients and algae sit mid-range for this region.
- Eutrophic
- #3 of 3 in the county
- Public access
- Limited data
Harmony Lake in Mercer County, North Dakota has a water quality grade of C (Fair). Water clarity: 2.3 ft visibility. Phosphorus: 67.5 µg/L. Chlorophyll-a (algae): 8.4 µg/L. Surface area: 44.9 acres.
- Clarity
- 2.3 ft
- Typical in August
- 61°F
- Area
- 45 acres
- Type
- Eutrophic
- Phosphorus
- 67.5 µg/L
- Chlorophyll-a
- 8.4 µg/L
- Public access
- Yes
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Watch Harmony Lake’s letter
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Harmony Lake is a 45-acre productive, nutrient-rich eutrophic lake in Mercer County, North Dakota. Water quality is graded C based on 3 sampling years through 2023. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 2 other monitored lakes in Mercer County, Harmony Lake ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, NDDEQ, last sampled 2023-10-17. Grade methodology: LakeQuality methodology.
What Harmony Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
Swimming Safety
Grade onlyLimited data
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
The C is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Water Quality Grade: C (Fair)
Very murky, less than 2.3 ft of visibility. Phosphorus 67.5 µg/L. Chlorophyll-a 8.4 µg/L. TSI 60. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.3 ft | Not graded |
| Phosphorus | 67.5 µg/L | Fair |
| Chlorophyll-a (Algae) | 8.4 µg/L | Good |
| Trophic State Index (TSI) | 60 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Water Temperature
Harmony Lake typically sits around 61°F at the surface in August. Summer average is about 61°F. Usually warmest in Jun (about 66°F) and coldest in Oct (about 49°F). These are typical values by month — not a live reading.
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 →
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 45 acres |
| Public Access | Yes |
No bathymetric survey has been published for Harmony Lake, so its depth is not documented here.
Recreation & Access
- Harmony LakePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Harmony Lake
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
County Ranking
Ranked #3 of 3 lakes in Mercer County
Nearby Lakes in Mercer County
Frequently asked questions about Harmony Lake
Where is Harmony Lake?
- Harmony Lake is a lake in Mercer County, North Dakota. LakeQuality grades it C for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Harmony Lake?
- Harmony Lake in Mercer County, North Dakota has a water quality grade of C (Fair). Water clarity: 2.3 ft visibility. Phosphorus: 67.5 µg/L. Chlorophyll-a (algae): 8.4 µg/L. Surface area: 44.9 acres.
Is Harmony Lake safe to swim in?
- The C is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Harmony Lake?
- Harmony Lake typically sits around 61°F at the surface in August, from 18 EPA Water Quality Portal field readings (2023–2023). That is a typical value for the month, not a live reading.
Are there boat ramps on Harmony Lake?
- Harmony Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Harmony Lake. Public access is listed as yes.
Explore Harmony Lake across LakeQuality
Species activity outlook by water temperature and season
Where to stay at North Dakota's top lakes, each with its grade
High nutrients, frequent algae, reduced clarity
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More North Dakota Lake Rankings
Other Grade C Lakes in North Dakota
Eutrophic Lakes in North Dakota
Where this data comes from
35 measurements from 3 monitoring stations, 2023. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- North Dakota Department Of Environmental Quality
21NDHDWQ_WQX35 samples · 2023
Analytical methods
- Phosphorus by Colorimetry
- 447.0 ~ EPA; Chlorophyll a and b in phytoplankton by HPLC/UV
- 4500 NO3 E ~ Nitrate in Water- Cadmium Reduction
Monitoring station identifiers (3)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Other records on this page
Depth, fish, and access data from North Dakota Game & Fish
Named boat-access points from the USGS National Boat Ramps inventory