Gascoyne Lake
Bowman County, North DakotaView mapDirections
Nutrients and algae run above the regional average.
- Eutrophic
- #3 of 4 in the county
- 14 ft max depth
- Public access
- Limited data
Gascoyne Lake in Bowman County, North Dakota has a water quality grade of D (Nutrient-rich). Water clarity: 1.3 ft visibility. Phosphorus: 90.5 µg/L. Chlorophyll-a (algae): 15.3 µg/L.
- Clarity
- 1.3 ft
- Typical in October
- 53°F
- Max depth
- ~14 ft est.
- Type
- Eutrophic
- Phosphorus
- 90.5 µg/L
- Chlorophyll-a
- 15.3 µg/L
- Public access
- Yes
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Gascoyne Lake is a 0-acre productive, nutrient-rich eutrophic lake in Bowman County, North Dakota with an estimated average depth of about 14 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. Compared to the 3 other monitored lakes in Bowman County, Gascoyne Lake ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, NDDEQ, last sampled 2023-10-10. Grade methodology: LakeQuality methodology.
What Gascoyne 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)
Very murky, less than 1.3 ft of visibility. Phosphorus 90.5 µg/L. Chlorophyll-a 15.3 µg/L. TSI 67. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.3 ft | Not graded |
| Phosphorus | 90.5 µg/L | Not graded |
| Chlorophyll-a (Algae) | 15.3 µg/L | Not graded |
| Trophic State Index (TSI) | 67 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Water Temperature
Gascoyne Lake typically sits around 53°F at the surface in October. Summer average is about 66°F. Usually warmest in Jul (about 70°F) and coldest in Oct (about 53°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 Gascoyne Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~14 ft est. |
| Average Depth | ~9 ft est. |
| 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 Gascoyne 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
- Gascoyne LakePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Gascoyne Lake
Reservoir Info (USACE NID)
Gascoyne Lake is a man-made reservoir impounded by the Gascoyne Lake Dam (completed 1934), built primarily for recreation on the Buffalo Creek-TR; earth-type dam, 8 ft tall and 1,265 ft long.
- Surface area
- 0 ac
- Normal storage
- 1,300 ac-ft
- Max storage
- 1,691 ac-ft
- Drainage area
- 4 sq mi
- Hazard class
- Low
- Owner
- Bowman County WRB
Source: USACE National Inventory of Dams, NID ID ND00375 · Operator website
Regulated Pollution Sources Nearby
2 EPA-permitted facilities operate within about 5 miles of Gascoyne Lake under Clean Water Act (NPDES) discharge permits.
- Gascoyne Materials H&RGascoyne · 2.3 mi away · NPDES ND0026182
- American Colloid Co GascoyneScranton · 2.7 mi away · NPDES ND0026077
Facilities permitted to discharge under the Clean Water Act within ~5 miles; proximity does not by itself mean a facility affects this lake. Source: EPA ECHO (ICIS-NPDES), as of 2026-07.
County Ranking
Ranked #3 of 4 lakes in Bowman County
Nearby Lakes in Bowman County
Frequently asked questions about Gascoyne Lake
Where is Gascoyne Lake?
- Gascoyne Lake is a lake in Bowman 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 Gascoyne Lake?
- Gascoyne Lake in Bowman County, North Dakota has a water quality grade of D (Nutrient-rich). Water clarity: 1.3 ft visibility. Phosphorus: 90.5 µg/L. Chlorophyll-a (algae): 15.3 µg/L.
Is Gascoyne 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 Gascoyne Lake?
- Gascoyne Lake typically sits around 53°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 Gascoyne Lake?
- No published bathymetric survey covers Gascoyne Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 14 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
Are there boat ramps on Gascoyne Lake?
- Gascoyne Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Gascoyne Lake. Public access is listed as yes.
Explore Gascoyne 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 D Lakes in North Dakota
Eutrophic 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
Regulated discharger data from EPA ECHO (ICIS-NPDES)
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