Cedar Lake
Slope County, North Dakota210 acresView mapDirections
Nutrients and algae sit mid-range for this region.
↑ up from F at the last regrade
- Hypereutrophic
- Impaired · Sediment / turbidity
- #2 of 2 in the county
- 12 ft max depth
- Public access
- Limited data
Cedar Lake in Slope County, North Dakota has a water quality grade of C (Fair). Water clarity: 1.3 ft visibility. Phosphorus: 136.5 µg/L. Chlorophyll-a (algae): 53.4 µg/L. Surface area: 210 acres.
- Clarity
- 1.3 ft
- Typical in October
- 47°F
- Max depth
- ~12 ft est.
- Area
- 210 acres
- Type
- Hypereutrophic
- Phosphorus
- 136.5 µg/L
- Chlorophyll-a
- 53.4 µg/L
- Public access
- Yes
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Cedar Lake is a 210-acre highly nutrient-loaded hypereutrophic lake in Slope County, North Dakota with an estimated average depth of about 12 feet. Water quality is graded C based on 1 sampling years through 2023. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 1 other monitored lakes in Slope County, Cedar Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, NDDEQ, last sampled 2023-10-10. Grade methodology: LakeQuality methodology.
What Cedar 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. Cedar Lake is listed impaired under Clean Water Act §303(d) (IR 5) for sediment / turbidity. Check local advisories before you swim.
Water Quality Grade: C (Fair)
Very murky, less than 1.3 ft of visibility. Phosphorus 136.5 µg/L. Chlorophyll-a 53.4 µg/L. TSI 73. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.3 ft | Not graded |
| Phosphorus | 136.5 µg/L | Not graded |
| Chlorophyll-a (Algae) | 53.4 µg/L | Not graded |
| Trophic State Index (TSI) | 73 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Water Temperature
Cedar Lake typically sits around 47°F at the surface in October. Summer average is about 67°F. Usually warmest in Jul (about 71°F) and coldest in Oct (about 47°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 14 field readings (2023–2023) via the EPA Water Quality Portal. See the full Cedar Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~12 ft est. |
| Average Depth | ~9 ft est. |
| Surface Area | 210 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 Cedar 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
- Cedar LakePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Cedar Lake
Reservoir Info (USACE NID)
Cedar Lake is a man-made reservoir impounded by the Cedar Lake Dam (completed 1935), built primarily for fish and wildlife pond on the Cedar Creek; earth-type dam, 23 ft tall and 723 ft long.
- Surface area
- 210 ac
- Normal storage
- 1,255 ac-ft
- Max storage
- 2,875 ac-ft
- Drainage area
- 208 sq mi
- Hazard class
- Low
- Owner
- ND Game & Fish
All listed purposes: Fish and Wildlife Pond;Recreation.
Source: USACE National Inventory of Dams, NID ID ND00122 · Operator website
EPA Impairment Status
Cedar Lake is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit ND-10130205-003-L_00 · Official waterbody report
County Ranking
Ranked #2 of 2 lakes in Slope County
Nearby Lakes in Slope County
Frequently asked questions about Cedar Lake
Where is Cedar Lake?
- Cedar Lake is a lake in Slope 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 Cedar Lake?
- Cedar Lake in Slope County, North Dakota has a water quality grade of C (Fair). Water clarity: 1.3 ft visibility. Phosphorus: 136.5 µg/L. Chlorophyll-a (algae): 53.4 µg/L. Surface area: 210 acres.
Is Cedar Lake safe to swim in?
- The C is nutrients and algae, not a swimming clearance. Cedar Lake is listed impaired under Clean Water Act §303(d) (IR 5) for sediment / turbidity. Check local advisories before you swim.
What is the water temperature of Cedar Lake?
- Cedar Lake typically sits around 47°F at the surface in October, from 14 EPA Water Quality Portal field readings (2023–2023). That is a typical value for the month, not a live reading.
How deep is Cedar Lake?
- No published bathymetric survey covers Cedar Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 12 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 210 acres.
Are there boat ramps on Cedar Lake?
- Cedar Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Cedar Lake. Public access is listed as yes.
Explore Cedar Lake across LakeQuality
Depth, room, public access, and the state wake-sport rules
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
North Dakota's cleanest and most-polluted lakes, ranked
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Other Grade C Lakes in North Dakota
Hypereutrophic Lakes in North Dakota
Where this data comes from
21 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_WQX21 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
Impairment status from EPA ATTAINS 303(d) database
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