Marlu Lake
Marlu Lake in Pope County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 4 ft visibility. Surface area: 320 acres.
- Clarity
- 4 ft
- Typical in August
- 78°F
- Mean depth
- ~12 ft est.
- Area
- 320 acres
- Trend
- ↑ Improving
- Public access
- No
- Ice-out
- Apr 10
- Open water
- 231 days
Next lake in Pope County
Why Marlu Lake has no grade
We grade a lake only when its monitoring record clears the evidence bar: 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 Marlu Lake, the only measurement available is water clarity, which is not a water-quality indicator on its own — EPA's National Lakes Assessment does not grade clarity. Sampling here has recorded water clarity, but not phosphorus and algae (chlorophyll-a).
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 MPCA and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Marlu Lake is a 320-acre lake in Pope County, Minnesota with an estimated average depth of about 12 feet. Overall water quality is improving over recent sampling years. Limited fish-species data available. No public access — the lake is private or restricted.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-10-11. Grade methodology: LakeGrade methodology.
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Swimming Safety
Not ratedLimited data
Not rated for swimming — there is not enough monitoring data to judge this lake
Water quality measurements for Marlu Lake
These readings exist but do not meet the evidence bar for an A–F grade — see why.
Murky, only visible to about 4 ft. Trophic State Index: 57.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 4 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 57 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Marlu Lake
Compare lakeside cabins, hotels, and vacation rentals near Marlu Lake in Pope 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.
Top-rated places to stay near Marlu Lake
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Water Temperature
Marlu Lake typically sits around 78°F at the surface in August. Summer average is about 75°F. Usually warmest in Aug (about 78°F) and coldest in Jun (about 71°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 19 field readings (2010–2025) via the EPA Water Quality Portal. See the full Marlu Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Average Depth | ~12 ft est. |
| Surface Area | 320 acres |
| Public Access | No |
Depth marked “est.” is a modeled estimate from HydroLAKES, not a measured survey. Minnesota has not published bathymetry for Marlu 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.
Fishing Marlu 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 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.058 m/yr | 6 |
Ice Season
Historical ice data from Minnesota DNR (27 observations).
Estimated open water season: 231 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2024-03-14 (2024) | 2018-05-01 (2018) |
| Ice-In | 2018-11-01 (2018) | 2024-01-03 (2024) |
Most recent ice-out: 2025-04-07
Reservoir Info (USACE NID)
Marlu Lake is a man-made reservoir impounded by the Marlu Mill Pond (completed 1967), built primarily for recreation on the Chippewa River E Branch; earth-type dam, 20 ft tall and 600 ft long.
- Surface area
- 320 ac
- Normal storage
- 995 ac-ft
- Max storage
- 2,184 ac-ft
- Drainage area
- 59 sq mi
- Hazard class
- Low
- Owner
- Morton, John
Source: USACE National Inventory of Dams, NID ID MN00896 · Operator website
Graded lakes near Marlu Lake
Marlu Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Pope County
Frequently asked questions about Marlu Lake
What is the water quality grade for Marlu Lake?
- Marlu Lake in Pope County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 4 ft visibility. Surface area: 320 acres.
Is Marlu Lake safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Marlu Lake is not rated for water quality — its monitoring record does not meet the evidence bar. Always check local health department advisories before swimming.
What is the water temperature of Marlu Lake?
- Marlu Lake typically sits around 78°F at the surface in August, from 19 EPA Water Quality Portal field readings (2010–2025). That is a typical value for the month, not a live reading.
How deep is Marlu Lake?
- No published bathymetric survey covers Marlu Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 12 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 320 acres.
When does Marlu Lake thaw?
- Marlu Lake typically has ice-out around Apr 10. Ice typically forms around Nov 27. The open water season is approximately 231 days.
Explore Marlu Lake across LakeGrade
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Where this data comes from
72 measurements from 1 monitoring station, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA72 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
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)
Lake details from Minnesota DNR LakeFinder
Ice data from Minnesota DNR Climate