Harmony Lake
Mercer County, North Dakota45 acresView mapDirections
ND DEQ publishes the water-quality measurements for Harmony Lake. Here is what has been measured.
- Eutrophic
- Public access
- Limited data
Harmony Lake in Mercer County, North Dakota has water-quality measurements published by ND DEQ, shown here as reported. Water clarity: 2.3 ft visibility. Phosphorus: 67.5 µg/L. Chlorophyll-a (algae): 8.4 µg/L. Surface area: 44.9 acres.
Harmony Lake is a 45-acre productive, nutrient-rich eutrophic lake in Mercer County, North Dakota. 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. Methodology: how these readings are compared.
What Harmony Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
Swimming conditions
Readings onlyLimited data
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Harmony Lake is safe to swim in today is a call for the North Dakota Department of Environmental Quality and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Harmony Lake
These are the measurements ND DEQ publishes for Harmony Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Very murky, less than 2.3 ft of visibility. Phosphorus 67.5 µg/L. Chlorophyll-a 8.4 µg/L. TSI 60.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 2.3ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 67.5µg/L | Fair GoodFairPoor |
| Chlorophyll-a (algae) | 8.4µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 60 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Harmony Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Harmony Lake typically sits around 49°F at the surface in October. 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.
Column height runs from this lake’s coldest month (49°F) to its warmest (66°F).
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
Surface area
45 acres
Public access
Yes
Listed by ND DEQ
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
Stays via Stay22
Stays near Harmony Lake
Compare lakeside cabins, hotels, and vacation rentals near Harmony Lake in Mercer County, North Dakota — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
Top-rated places to stay near Harmony Lake
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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
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. Its water-quality measurements are published by ND DEQ and shown on this page as reported.
What is the water quality of Harmony Lake?
- Harmony Lake in Mercer County, North Dakota has water-quality measurements published by ND DEQ, shown here as reported. 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?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Harmony Lake?
- Harmony Lake typically sits around 49°F at the surface in October, 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.
Can I fish at Harmony Lake?
- Harmony Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Seasons, size and bag limits, and whether you need a license are set by North Dakota's fish and wildlife agency, so check its current regulations before you go.
Explore Harmony Lake across LakeQuality
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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)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from 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