Demontreville Lake
Demontreville Lake in Washington County, Minnesota has a water quality grade of C (Fair). Water clarity: 10.2 ft visibility. Phosphorus: 25.5 µg/L. Chlorophyll-a (algae): 11 µg/L. Maximum depth: 24 ft. Surface area: 157.06 acres.
- Clarity
- 10.2 ft
- Typical in August
- 73°F
- Max depth
- 24 ft
- Area
- 157 acres
- Type
- Mesotrophic
- Trend
- ↑ Improving
- Public access
- Yes
- Ice-out
- Apr 3
- Open water
- 237 days
Next lake in Washington County
Demontreville Lake is a 157-acre mesotrophic lake in Washington County, Minnesota with a maximum depth of 24 feet. Water quality is graded C based on 2 sampling years through 2024. Overall water quality is improving over recent sampling years. The lake supports 12 documented fish species including black bullhead, black crappie, and bluegill. Public access is available with 1 public boat landing. Compared to the 74 other monitored lakes in Washington County, Demontreville Lake ranks #45 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-10-08. Grade methodology: LakeGrade methodology.
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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.
Generally safe for swimming, moderate water quality
Water Quality Grade: C (Fair)
Good clarity, visible to about 10.2 ft. Phosphorus level: 25.5 µg/L. Chlorophyll-a: 11 µg/L. Trophic State Index: 50.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 10.2 ft | Not graded |
| Phosphorus | 25.5 µg/L | Fair |
| Chlorophyll-a (Algae) | 11 µg/L | Fair |
| Trophic State Index (TSI) | 50 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Demontreville Lake
Compare lakeside cabins, hotels, and vacation rentals near Demontreville Lake in Washington County, Minnesota — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
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Water Temperature
Demontreville Lake typically sits around 73°F at the surface in August. Summer average is about 70°F. Usually warmest in Jul (about 75°F) and coldest in Feb (about 39°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 128 field readings (2010–2024) via the EPA Water Quality Portal. See the full Demontreville Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 24 ft |
| Surface Area | 157 acres |
| Shoreline Length | 3.4 mi |
| Littoral Zone | 82% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Lake DeMontrevillePublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Demontreville Lake
Invasive & Introduced Species
Red chips are ecologically harmful invasive species. Gray chips are stocked or introduced fish that aren't a current ecological concern.
Water Quality Trend: ↑ Improving
Based on 3 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.155 m/yr | 3 |
Ice Season
Historical ice data from Minnesota DNR (29 observations).
Estimated open water season: 237 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2024-03-03 (2024) | 1978-04-12 (1978) |
| Ice-In | 1991-11-02 (1991) | 2001-12-20 (2001) |
Most recent ice-out: 2024-03-03
EPA Impairment Status
Demontreville Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN82-0101-00 · Official waterbody report
County Ranking
Ranked #45 of 75 lakes in Washington County
Nearby Lakes in Washington County
Frequently asked questions about Demontreville Lake
What is the water quality grade for Demontreville Lake?
- Demontreville Lake in Washington County, Minnesota has a water quality grade of C (Fair). Water clarity: 10.2 ft visibility. Phosphorus: 25.5 µg/L. Chlorophyll-a (algae): 11 µg/L. Maximum depth: 24 ft. Surface area: 157.06 acres.
Is Demontreville Lake safe to swim in?
- Generally safe for swimming, moderate water quality. Demontreville Lake has a water quality grade of C (Fair). Algae concentration (chlorophyll-a) is 11 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Demontreville Lake?
- Demontreville Lake typically sits around 73°F at the surface in August, from 128 EPA Water Quality Portal field readings (2010–2024). That is a typical value for the month, not a live reading.
How deep is Demontreville Lake?
- Demontreville Lake has a maximum depth of 24 feet. The lake covers 157.06 acres.
What fish are in Demontreville Lake?
- Fish species found in Demontreville Lake include black bullhead, black crappie, bluegill, brown bullhead, green sunfish, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, white crappie, yellow bullhead, yellow perch. Demontreville Lake is located in Washington County, Minnesota.
When does Demontreville Lake thaw?
- Demontreville Lake typically has ice-out around Apr 3. Ice typically forms around Nov 26. The open water season is approximately 237 days.
Are there boat ramps on Demontreville Lake?
- Demontreville Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Lake DeMontreville. Public access is listed as yes.
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Where this data comes from
42 measurements from 1 monitoring station, 2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA42 samples · 2024
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Colorimetry
- Analysis of Chlorophyll in Periphyton and Plankton
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
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory
Ice data from Minnesota DNR Climate