Tolna Dam Lake
Nelson County, North Dakota166 acresView mapDirections
Not Rated: one monitoring station are on record, but they measured water clarity only. LakeQuality’s A–F method grades total phosphorus, total nitrogen, chlorophyll-a, and turbidity; clarity is shown, not scored.
- 65 ft max depth
- Public access
- Limited data
Tolna Dam Lake in Nelson County, North Dakota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 4.9 ft visibility. Surface area: 166.3 acres.
- Clarity
- 4.9 ft
- Typical in August
- 71°F
- Max depth
- ~65 ft est.
- Area
- 166 acres
- Public access
- Yes
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Watch Tolna Dam Lake’s letter
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Why Tolna Dam Lake has no grade
Tolna Dam Lake has monitoring on record from one station, but only water clarity was measured. LakeQuality’s A–F letter uses total phosphorus, total nitrogen, chlorophyll-a, and turbidity against EPA National Lakes Assessment condition classes. With none of those grading measurements on record, Tolna Dam Lake is Not Rated — not an F. Its 4.9-foot median from 8 readings collected 2025 is still shown as clarity, but clarity alone cannot earn a letter.
Not Rated is EPA Integrated Reporting Category 3 — insufficient information. Everything below that has been measured is still reported on this page.
Sampling is run by NDDEQ and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Tolna Dam Lake is a 166-acre lake in Nelson County, North Dakota with an estimated average depth of about 65 feet. Limited fish-species data available. Public access is available with 1 public boat landing.
Source: EPA Water Quality Portal sampling records, NDDEQ, last sampled 2025-10-13. Grade methodology: LakeQuality methodology.
What Tolna Dam Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
Swimming Safety
Not ratedLimited data
The letter is not a swimming clearance. Check local advisories before you swim.
Water quality measurements for Tolna Dam Lake
These readings exist but are not enough for an A–F grade — see why.
Murky, only visible to about 4.9 ft. TSI 54.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 4.9 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 54 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Water Temperature
Tolna Dam Lake typically sits around 71°F at the surface in August. Summer average is about 67°F. Usually warmest in Aug (about 71°F) and coldest in Oct (about 55°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 12 field readings (2010–2025) via the EPA Water Quality Portal. See the full Tolna Dam Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~65 ft est. |
| Average Depth | ~14 ft est. |
| Surface Area | 166 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 Tolna 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
- Tolna DamPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Tolna Dam Lake
Reservoir Info (USACE NID)
Tolna Dam Lake is a man-made reservoir impounded by the Tolna Dam 1 (completed 1936), built primarily for recreation on the Tolna Coulee; earth-type dam, 36 ft tall and 520 ft long.
- Surface area
- 166.3 ac
- Normal storage
- 2,027 ac-ft
- Max storage
- 3,080 ac-ft
- Drainage area
- 40 sq mi
- Hazard class
- Significant
- Owner
- Nelson County WRB
Source: USACE National Inventory of Dams, NID ID ND00027 · Operator website · Matched by proximity (0.27 km)
Graded lakes near Tolna Dam Lake
Tolna Dam Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Nelson County
Frequently asked questions about Tolna Dam Lake
Where is Tolna Dam Lake?
- Tolna Dam Lake is a lake in Nelson County, North Dakota. LakeQuality has not rated this lake (UNRATED) — no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years).
What is the water quality grade for Tolna Dam Lake?
- Tolna Dam Lake in Nelson County, North Dakota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 4.9 ft visibility. Surface area: 166.3 acres.
Is Tolna Dam Lake safe to swim in?
- The letter is not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Tolna Dam Lake?
- Tolna Dam Lake typically sits around 71°F at the surface in August, from 12 EPA Water Quality Portal field readings (2010–2025). That is a typical value for the month, not a live reading.
How deep is Tolna Dam Lake?
- No published bathymetric survey covers Tolna Dam Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 65 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 166.3 acres.
Are there boat ramps on Tolna Dam Lake?
- Tolna Dam Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Tolna Dam. Public access is listed as yes.
Explore Tolna Dam Lake across LakeQuality
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Where this data comes from
8 measurements from 1 monitoring station, 2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- North Dakota Department Of Environmental Quality
21NDHDWQ_WQX8 samples · 2025
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
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