Larimore Dam Lake
Grand Forks County, North Dakota72 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 2 in the county
- 28 ft max depth
- Public access
Larimore Dam Lake in Grand Forks County, North Dakota has a water quality grade of C (Fair). Water clarity: 3 ft visibility. Phosphorus: 225 µg/L. Chlorophyll-a (algae): 13.3 µg/L. Surface area: 72 acres.
- Clarity
- 3 ft
- Typical in September
- 58°F
- Max depth
- ~28 ft est.
- Area
- 72 acres
- Type
- Eutrophic
- Phosphorus
- 225 µg/L
- Chlorophyll-a
- 13.3 µg/L
- Trend
- ↑ Improving
- Public access
- Yes
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Larimore Dam Lake is a 72-acre productive, nutrient-rich eutrophic lake in Grand Forks County, North Dakota with an estimated average depth of about 28 feet. Water quality is graded C based on 3 sampling years through 2025. Overall water quality is improving over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 1 other monitored lakes in Grand Forks County, Larimore Dam Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, NDDEQ, last sampled 2025-10-13. Grade methodology: LakeQuality methodology.
What Larimore Dam Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
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. Larimore Dam Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Water Quality Grade: C (Fair)
Very murky, less than 3 ft of visibility. Phosphorus 225 µg/L. Chlorophyll-a 13.3 µg/L. TSI 66. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3 ft | Not graded |
| Phosphorus | 225 µg/L | Poor |
| Chlorophyll-a (Algae) | 13.3 µg/L | Good |
| Trophic State Index (TSI) | 66 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Water Temperature
Larimore Dam Lake typically sits around 58°F at the surface in September. Summer average is about 65°F. Usually warmest in Aug (about 68°F) and coldest in Oct (about 51°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 51 field readings (2020–2025) via the EPA Water Quality Portal. See the full Larimore Dam Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~28 ft est. |
| Average Depth | ~10 ft est. |
| Surface Area | 72 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 Larimore 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
- Larimore DamPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Larimore Dam Lake
Water Quality Trend: ↑ Improving
Based on 4 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.04 m/yr | 4 |
| Phosphorus | ↑ Improving | -102 µg/L/yr | 2 |
| Chlorophyll-a | ↑ Improving | -11.54 µg/L/yr | 3 |
Reservoir Info (USACE NID)
Larimore Dam Lake is a man-made reservoir impounded by the Upper Turtle River Flood Ret. 9 (completed 1979), built primarily for flood risk reduction on the South Branch Turtle River; earth-type dam, 71 ft tall and 1,040 ft long.
- Surface area
- 72 ac
- Normal storage
- 823 ac-ft
- Max storage
- 10,410 ac-ft
- Drainage area
- 64.9 sq mi
- Hazard class
- High
- Owner
- Grand Forks County WRB
All listed purposes: Flood Risk Reduction;Recreation.
Source: USACE National Inventory of Dams, NID ID ND00391 · Operator website
EPA Impairment Status
Larimore Dam 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-09020307-001-L_00 · Official waterbody report · Matched by proximity (0.06 km)
County Ranking
Ranked #1 of 2 lakes in Grand Forks County
Nearby Lakes in Grand Forks County
Frequently asked questions about Larimore Dam Lake
Where is Larimore Dam Lake?
- Larimore Dam Lake is a lake in Grand Forks 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 Larimore Dam Lake?
- Larimore Dam Lake in Grand Forks County, North Dakota has a water quality grade of C (Fair). Water clarity: 3 ft visibility. Phosphorus: 225 µg/L. Chlorophyll-a (algae): 13.3 µg/L. Surface area: 72 acres.
Is Larimore Dam Lake safe to swim in?
- The C is nutrients and algae, not a swimming clearance. Larimore Dam Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
What is the water temperature of Larimore Dam Lake?
- Larimore Dam Lake typically sits around 58°F at the surface in September, from 51 EPA Water Quality Portal field readings (2020–2025). That is a typical value for the month, not a live reading.
How deep is Larimore Dam Lake?
- No published bathymetric survey covers Larimore Dam Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 28 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 72 acres.
Are there boat ramps on Larimore Dam Lake?
- Larimore Dam Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Larimore Dam. Public access is listed as yes.
Explore Larimore 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
High nutrients, frequent algae, reduced clarity
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Other Grade C Lakes in North Dakota
Eutrophic Lakes in North Dakota
Where this data comes from
75 measurements from 3 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_WQX75 samples · 2020–2025
Analytical methods
- Phosphorus by Colorimetry
- 447.0 ~ EPA; Chlorophyll a and b in phytoplankton by HPLC/UV
- 10200 H ~ Chlorophyll a-b-c Determination
- 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
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