Sprague Lake
Sargent County, North Dakota58 acresView mapDirections
Not enough samples to grade — no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years). No letter yet. Here is what we do have.
- 63 ft max depth
- Public access
- Limited data
Sprague Lake in Sargent County, North Dakota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 1.6 ft visibility. Chlorophyll-a (algae): 43.4 µg/L. Surface area: 58 acres.
- Clarity
- 1.6 ft
- Typical in October
- 49°F
- Max depth
- ~63 ft est.
- Area
- 58 acres
- Public access
- Yes
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Watch Sprague Lake’s letter
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Why Sprague Lake has no grade
We grade a lake only when the monitoring record supports a letter: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For Sprague Lake, no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years). Sampling here has recorded water clarity and algae (chlorophyll-a), but not phosphorus.
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. 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.
Sprague Lake is a 58-acre lake in Sargent County, North Dakota with an estimated average depth of about 63 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 2020-10-02. Grade methodology: LakeQuality methodology.
What Sprague 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 Sprague Lake
These readings exist but are not enough for an A–F grade — see why.
Very murky, less than 1.6 ft of visibility. Chlorophyll-a 43.4 µg/L. TSI 69.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.6 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | 43.4 µg/L | Not graded |
| Trophic State Index (TSI) | 69 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Water Temperature
Sprague Lake typically sits around 49°F at the surface in October. Summer average is about 67°F. Usually warmest in Jul (about 71°F) and coldest in Oct (about 49°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 15 field readings (2010–2020) via the EPA Water Quality Portal. See the full Sprague Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~63 ft est. |
| Average Depth | ~7 ft est. |
| Surface Area | 58 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 Sprague 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
- Sprague LakePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Sprague Lake
Reservoir Info (USACE NID)
Sprague Lake is a man-made reservoir impounded by the Lake Mann Dam (completed 1965), built primarily for fish and wildlife pond on the Wild Rice River; earth-type dam, 9 ft tall and 784 ft long.
- Surface area
- 58 ac
- Normal storage
- 475 ac-ft
- Max storage
- 658 ac-ft
- Drainage area
- 0.18 sq mi
- Hazard class
- Low
- Owner
- US FISH AND WILDLIFE SERVICE
Source: USACE National Inventory of Dams, NID ID ND00900 · Operator website · Matched by proximity (0.8 km)
Nearby Lakes in Sargent County
Frequently asked questions about Sprague Lake
Where is Sprague Lake?
- Sprague Lake is a lake in Sargent 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 Sprague Lake?
- Sprague Lake in Sargent County, North Dakota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 1.6 ft visibility. Chlorophyll-a (algae): 43.4 µg/L. Surface area: 58 acres.
Is Sprague Lake safe to swim in?
- The letter is not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Sprague Lake?
- Sprague Lake typically sits around 49°F at the surface in October, from 15 EPA Water Quality Portal field readings (2010–2020). That is a typical value for the month, not a live reading.
How deep is Sprague Lake?
- No published bathymetric survey covers Sprague Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 63 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 58 acres.
Are there boat ramps on Sprague Lake?
- Sprague Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Sprague Lake. Public access is listed as yes.
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Where this data comes from
9 measurements from 1 monitoring station, 2020. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- North Dakota Department Of Environmental Quality
21NDHDWQ_WQX9 samples · 2020
Analytical methods
- 447.0 ~ EPA; Chlorophyll a and b in phytoplankton by HPLC/UV
- 10200 H ~ Chlorophyll a-b-c Determination
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