Lake Marie is a 30-acre mesotrophic lake in Mercer County, Missouri. Water quality is graded B based on 3 sampling years through 2023. Overall water quality is improving over recent sampling years. Limited fish-species data available. Public access is available. Compared to the 1 other monitored lakes in Mercer County, Lake Marie ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Missouri DNR, last sampled 2023-08-01. Grade methodology: LakeGrade methodology.
Watch Lake Marie water quality
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Swimming Safety
Good for swimming, clear water with low algae levels
Water Quality Grade: B, Good
Moderate clarity, visible to about 7.8 ft. Phosphorus level: 13 µg/L. Chlorophyll-a: 2.7 µg/L. Trophic State Index: 43.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 7.8 ft | C |
| Phosphorus | 13 µg/L | A |
| Chlorophyll-a (Algae) | 2.7 µg/L | A |
| Trophic State Index (TSI) | 43 | Mesotrophic |
Moderate nutrients, good water quality
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 30 acres |
| Public Access | Yes |
Where to stay near Lake Marie
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Fishing Lake Marie
Water Quality Trend: ↑ Improving
Based on 3 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.955 m/yr | 3 |
| Phosphorus | ↑ Improving | -2.05 µg/L/yr | 3 |
| Chlorophyll-a | ↑ Improving | -1.1 µg/L/yr | 3 |
Water Temperature
Lake Marie averages about 81°F at the surface in summer, usually warmest in Jul (about 83°F) and coldest in May (about 70°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 12 field readings (2021–2023) via the EPA Water Quality Portal. See the full Lake Marie water temperature breakdown →
Location
County Ranking
Ranked #1 of 2 lakes in Mercer County
Nearby Lakes in Mercer County
Explore Lake Marie across LakeGrade
More Missouri Lake Rankings
Other Grade B Lakes in Missouri
Mesotrophic Lakes in Missouri
More records, surveys & data sources
Reservoir Info (USACE NID)
Lake Marie is a man-made reservoir impounded by the Lake Marie Dam (completed 1981), built primarily for recreation on the POPS BRANCH; earth-type dam, 50 ft tall and 1,100 ft long.
- Surface area
- 30 ac
- Normal storage
- 882 ac-ft
- Max storage
- 970 ac-ft
- Drainage area
- 0.53 sq mi
- Hazard class
- High
- Owner
- LAKE MARIE HOA
Source: USACE National Inventory of Dams, NID ID MO10154 · Operator website
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Regulated Pollution Sources Nearby
2 EPA-permitted facilities operate within about 5 miles of Lake Marie under Clean Water Act (NPDES) discharge permits. 2 facilities have a reported Clean Water Act violation in the past three years.
- Twin Lakes WwtfMercer · 0.2 mi away · NPDES MO0129216Recent violation
- Mercer WwtfMercer · 2.2 mi away · NPDES MO0056057Recent violation
Facilities permitted to discharge under the Clean Water Act within ~5 miles; proximity does not by itself mean a facility affects this lake. Source: EPA ECHO (ICIS-NPDES), as of 2026-07.
Data Sources
Water quality data from the EPA Water Quality Portal
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grading methodology based on Metropolitan Council standards
Most recent sample: 2023-08-01
Monitoring stations: 1