Froelich Dam Lake
Sioux County, North Dakota175 acresView mapDirections
Nutrients and algae run above the regional average.
- Hypereutrophic
- #1 of 1 in the county
- 20 ft max depth
- Public access
- Limited data
Froelich Dam Lake in Sioux County, North Dakota has a water quality grade of D (Nutrient-rich). Water clarity: 3.9 ft visibility. Phosphorus: 311.5 µg/L. Chlorophyll-a (algae): 37.5 µg/L. Surface area: 175 acres.
- Clarity
- 3.9 ft
- Typical in September
- 62°F
- Max depth
- ~20 ft est.
- Area
- 175 acres
- Type
- Hypereutrophic
- Public access
- Yes
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Stays near Froelich Dam Lake
Compare lakeside cabins, hotels, and vacation rentals near Froelich Dam Lake in Sioux 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. The water-quality grade measures nutrients and algae, not lodging — cabins and rentals around Froelich Dam Lake are listed below.
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Froelich Dam Lake is a 175-acre highly nutrient-loaded hypereutrophic lake in Sioux County, North Dakota with an estimated average depth of about 20 feet. Water quality is graded D based on 1 sampling years through 2023. Limited fish-species data available. Public access is available with 1 public boat landing.
Source: EPA Water Quality Portal sampling records, NDDEQ, last sampled 2023-10-20. Grade methodology: LakeQuality methodology.
What Froelich Dam 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 D is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Water Quality Grade: D (Nutrient-rich)
Murky, only visible to about 3.9 ft. Phosphorus 311.5 µg/L. Chlorophyll-a 37.5 µg/L. TSI 70. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3.9 ft | Not graded |
| Phosphorus | 311.5 µg/L | Not graded |
| Chlorophyll-a (Algae) | 37.5 µg/L | Not graded |
| Trophic State Index (TSI) | 70 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Water Temperature
Froelich Dam Lake typically sits around 62°F at the surface in September. Summer average is about 69°F. Usually warmest in Jul (about 73°F) and coldest in Oct (about 48°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 67 field readings (2017–2023) via the EPA Water Quality Portal. See the full Froelich Dam Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~20 ft est. |
| Average Depth | ~10 ft est. |
| Surface Area | 175 acres |
| Public Access | Yes |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. North Dakota has not published bathymetry for Froelich Dam Lake.
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Recreation & Access
- Froelich DamPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Froelich Dam Lake
Reservoir Info (USACE NID)
Froelich Dam Lake is a man-made reservoir impounded by the Froelich Dam (completed 1962), built primarily for recreation on the Porcupine Creek-TR; earth-type dam, 46 ft tall and 821 ft long.
- Surface area
- 175 ac
- Normal storage
- 2,271.3 ac-ft
- Max storage
- 4,212.9 ac-ft
- Drainage area
- 68.3 sq mi
- Hazard class
- Low
- Owner
- ND Game & Fish
All listed purposes: Recreation;Fire Protection, Stock, Or Small Fish Pond.
Source: USACE National Inventory of Dams, NID ID ND00025 · Operator website
County Ranking
Ranked #1 of 1 lakes in Sioux County
Nearby Lakes in Sioux County
Frequently asked questions about Froelich Dam Lake
Where is Froelich Dam Lake?
- Froelich Dam Lake is a lake in Sioux County, North Dakota. LakeQuality grades it D for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Froelich Dam Lake?
- Froelich Dam Lake in Sioux County, North Dakota has a water quality grade of D (Nutrient-rich). Water clarity: 3.9 ft visibility. Phosphorus: 311.5 µg/L. Chlorophyll-a (algae): 37.5 µg/L. Surface area: 175 acres.
Is Froelich Dam Lake safe to swim in?
- The D is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Froelich Dam Lake?
- Froelich Dam Lake typically sits around 62°F at the surface in September, from 67 EPA Water Quality Portal field readings (2017–2023). That is a typical value for the month, not a live reading.
How deep is Froelich Dam Lake?
- No published bathymetric survey covers Froelich Dam Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 20 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate. The lake covers 175 acres.
Are there boat ramps on Froelich Dam Lake?
- Froelich Dam Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Froelich Dam. Public access is listed as yes.
Explore Froelich Dam Lake across LakeQuality
Species activity outlook by water temperature and season
Where to stay at North Dakota's top lakes, each with its grade
Very high nutrients, dense algae, poor clarity
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Where this data comes from
19 measurements from 1 monitoring station, 2023. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- North Dakota Department Of Environmental Quality
21NDHDWQ_WQX19 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 (1)
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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Depth, fish, and access data from North Dakota Game & Fish
Named boat-access points from the USGS National Boat Ramps inventory