Patterson Lake
Stark County, North DakotaView mapDirections
Nutrients and algae sit mid-range for this region.
↓ down from B at the last regrade
- Eutrophic
- Impaired · Nutrients (phosphorus, nitrogen)
- #3 of 3 in the county
- Public access
- Limited data
Patterson Lake in Stark County, North Dakota has a water quality grade of C (Fair). Phosphorus: 293.5 µg/L. Chlorophyll-a (algae): 7.8 µg/L.
- Type
- Eutrophic
- Public access
- Yes
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Patterson Lake is a productive, nutrient-rich eutrophic lake in Stark County, North Dakota. Water quality is graded C based on 3 sampling years through 2023. Limited fish-species data available. Public access is available. Compared to the 2 other monitored lakes in Stark County, Patterson Lake ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, NDDEQ, last sampled 2023-07-14. Grade methodology: LakeQuality methodology.
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. Patterson Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen), sediment / turbidity, turbidity. Check local advisories before you swim.
Water Quality Grade: C (Fair)
No clarity data. Phosphorus 293.5 µg/L. Chlorophyll-a 7.8 µg/L. TSI 68. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | 293.5 µg/L | Poor |
| Chlorophyll-a (Algae) | 7.8 µg/L | Good |
| Trophic State Index (TSI) | 68 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Fishing Patterson Lake
EPA Impairment Status
Patterson Lake is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit ND-10130202-002-L_00 · Official waterbody report
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Patterson Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Richardton City OfRichardton · 3.2 mi away · NPDES ND0020109Recent violation
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 3 lakes in Stark County
Nearby Lakes in Stark County
Frequently asked questions about Patterson Lake
Where is Patterson Lake?
- Patterson Lake is a lake in Stark 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 Patterson Lake?
- Patterson Lake in Stark County, North Dakota has a water quality grade of C (Fair). Phosphorus: 293.5 µg/L. Chlorophyll-a (algae): 7.8 µg/L.
Is Patterson Lake safe to swim in?
- The C is nutrients and algae, not a swimming clearance. Patterson Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen), sediment / turbidity, turbidity. Check local advisories before you swim.
Explore Patterson 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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Planning a trip around Theodore Roosevelt?
Patterson Lake is about 35 miles from Theodore Roosevelt National Park. Crowds there swing hard by season, so the month you pick changes both how busy the park is and what lodging costs.
Best time to visit Theodore Roosevelt →More North Dakota Lake Rankings
Other Grade C Lakes in North Dakota
Eutrophic Lakes in North Dakota
Where this data comes from
15 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_WQX15 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
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)