Jamestown Reservoir
Stutsman County, North Dakota17,427 acresView mapDirections
Nutrients and algae sit mid-range for this region.
↑ up from D at the last regrade
- Eutrophic
- Impaired · Nutrients (phosphorus, nitrogen)
- #1 of 3 in the county
- Public access
Jamestown Reservoir in Stutsman County, North Dakota has a water quality grade of C (Fair). Water clarity: 7.2 ft visibility. Phosphorus: 527 µg/L. Chlorophyll-a (algae): 8.6 µg/L. Surface area: 17427 acres.
- Clarity
- 7.2 ft
- Typical in September
- 66°F
- Area
- 17,427 acres
- Type
- Eutrophic
- Phosphorus
- 527 µg/L
- Chlorophyll-a
- 8.6 µg/L
- Public access
- Yes
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Watch Jamestown Reservoir’s letter
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Jamestown Reservoir is a 17,427-acre productive, nutrient-rich eutrophic lake in Stutsman County, North Dakota. Water quality is graded C based on 3 sampling years through 2025. Limited fish-species data available. Public access is available with 4 public boat landings. Compared to the 2 other monitored lakes in Stutsman County, Jamestown Reservoir ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, NDDEQ, last sampled 2025-09-23. Grade methodology: LakeQuality methodology.
What Jamestown Reservoir is good for
From access and monitoring records, not editorial picks.
- Boat launch4 documented ramps
- Big water17,427 acres
Swimming Safety
Grade onlyModerate
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. Jamestown Reservoir is listed impaired under Clean Water Act §303(d) (IR 5) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Water Quality Grade: C (Fair)
Moderate clarity, visible to about 7.2 ft. Phosphorus 527 µg/L. Chlorophyll-a 8.6 µg/L. TSI 65. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 7.2 ft | Not graded |
| Phosphorus | 527 µg/L | Poor |
| Chlorophyll-a (Algae) | 8.6 µg/L | Good |
| Trophic State Index (TSI) | 65 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Water Temperature
Jamestown Reservoir typically sits around 66°F at the surface in September. Summer average is about 70°F. Usually warmest in Jul (about 74°F) and coldest in Oct (about 54°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 369 field readings (2012–2025) via the EPA Water Quality Portal. See the full Jamestown Reservoir water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 17,427 acres |
| Public Access | Yes |
No bathymetric survey has been published for Jamestown Reservoir, so its depth is not documented here.
Recreation & Access
- Jamestown ReservoirPublic
- Jamestown ReservoirPublic
- Jamestown ReservoirPublic
- Jamestown ReservoirPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Jamestown Reservoir
Reservoir Info (USACE NID)
Jamestown Reservoir is a man-made reservoir impounded by the Jamestown Dam (completed 1954), built primarily for flood risk reduction on the JAMES RIVER; earth-type dam, 110 ft tall and 1,418 ft long.
- Surface area
- 17,427 ac
- Normal storage
- 35,535 ac-ft
- Max storage
- 379,636 ac-ft
- Drainage area
- 1,573.65 sq mi
- Hazard class
- High
- Owner
- BUREAU OF RECLAMATION
All listed purposes: Flood Risk Reduction;Irrigation.
Source: USACE National Inventory of Dams, NID ID ND00151 · Operator website
EPA Impairment Status
Jamestown Reservoir 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-10160001-002-L_00 · Official waterbody report
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Jamestown Reservoir under Clean Water Act (NPDES) discharge permits, including 1 classified by the EPA as major discharger. 1 facility has a reported Clean Water Act violation in the past three years.
- Jamestown City OfJamestown · 3.9 mi away · NPDES ND0023370MajorRecent 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 #1 of 3 lakes in Stutsman County
Nearby Lakes in Stutsman County
Frequently asked questions about Jamestown Reservoir
Where is Jamestown Reservoir?
- Jamestown Reservoir is a lake in Stutsman 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 Jamestown Reservoir?
- Jamestown Reservoir in Stutsman County, North Dakota has a water quality grade of C (Fair). Water clarity: 7.2 ft visibility. Phosphorus: 527 µg/L. Chlorophyll-a (algae): 8.6 µg/L. Surface area: 17427 acres.
Is Jamestown Reservoir safe to swim in?
- The C is nutrients and algae, not a swimming clearance. Jamestown Reservoir is listed impaired under Clean Water Act §303(d) (IR 5) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
What is the water temperature of Jamestown Reservoir?
- Jamestown Reservoir typically sits around 66°F at the surface in September, from 369 EPA Water Quality Portal field readings (2012–2025). That is a typical value for the month, not a live reading.
Are there boat ramps on Jamestown Reservoir?
- Jamestown Reservoir has 4 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Jamestown Reservoir, Jamestown Reservoir, Jamestown Reservoir, Jamestown Reservoir. Public access is listed as yes.
Explore Jamestown Reservoir 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
High nutrients, frequent algae, reduced clarity
North Dakota's cleanest and most-polluted lakes, ranked
More North Dakota Lake Rankings
Other Grade C Lakes in North Dakota
Eutrophic Lakes in North Dakota
Where this data comes from
232 measurements from 4 monitoring stations, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- North Dakota Department Of Environmental Quality
21NDHDWQ_WQX217 samples · 2021–2025 - USGS North Dakota Water Science Center
USGS-ND15 samples · 2020–2023
Analytical methods
- P, wu, WCA, persulfate CF color
- Plant pigments, sonication & 445
- 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 (4)
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)
Depth, fish, and access data from North Dakota Game & Fish
Named boat-access points from the USGS National Boat Ramps inventory