Lake Capri is a 112-acre cold, clear oligotrophic lake in St. Francois County, Missouri. Water quality is graded A based on 3 sampling years through 2025. Overall water quality is improving over recent sampling years. Compared to the 3 other monitored lakes in St. Francois County, Lake Capri ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Missouri DNR, last sampled 2025-07-29. Grade methodology: LakeGrade methodology.
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Swimming Safety
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A, Excellent
Crystal clear, you can see 16.3 ft down. Phosphorus level: 5.7 µg/L. Chlorophyll-a: 0.9 µg/L. Trophic State Index: 32.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 16.3 ft | A |
| Phosphorus | 5.7 µg/L | A |
| Chlorophyll-a (Algae) | 0.9 µg/L | A |
| Trophic State Index (TSI) | 32 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 112 acres |
Where to stay near Lake Capri
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Fishing Lake Capri
Water Quality Trend: ↑ Improving
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.098 m/yr | 4 |
| Phosphorus | ↓ Declining | +0.46 µg/L/yr | 6 |
| Chlorophyll-a | ↑ Improving | -0.28 µg/L/yr | 5 |
Water Temperature
Lake Capri averages about 81°F at the surface in summer, usually warmest in Jul (about 83°F) and coldest in May (about 73°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 60 field readings (2010–2024) via the EPA Water Quality Portal. See the full Lake Capri water temperature breakdown →
Location
County Ranking
Ranked #1 of 4 lakes in St. Francois County
Nearby Lakes in St. Francois County
Explore Lake Capri across LakeGrade
Species activity outlook by water temperature and season
Where to stay at Missouri's top lakes, each with its grade
Low nutrients, clear water, excellent for swimming
Missouri's cleanest and most-polluted lakes, ranked
More Missouri Lake Rankings
Other Grade A Lakes in Missouri
Washington County · Clarity: 11.1 ft
Ste. Genevieve County · Clarity: 9.9 ft
Iron County · Clarity: 13.1 ft
Jefferson County · Clarity: 12.9 ft
Perry County · Clarity: 12 ft
Warren County · Clarity: 12.6 ft
Oligotrophic Lakes in Missouri
More records, surveys & data sources
Reservoir Info (USACE NID)
Lake Capri is a man-made reservoir impounded by the Lac Capri Dam (completed 1972), built primarily for recreation on the TR BIG RIVER; earth-type dam, 97 ft tall and 2,170 ft long.
- Surface area
- 112 ac
- Normal storage
- 2,828 ac-ft
- Max storage
- 3,541 ac-ft
- Drainage area
- 0.99 sq mi
- Hazard class
- High
- Owner
- TERRE DU LAC POA
Source: USACE National Inventory of Dams, NID ID MO30063 · Operator website · Matched by proximity (0.04 km)
EPA Impairment Status
Lake Capri is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit MO_7297.00 · Official waterbody report · Matched by proximity (0.28 km)
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Lake Capri under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Terre Du Lac South One Cell LagoonBonne Terre · 1.1 mi away · NPDES MO0057312Recent 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
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grading methodology based on Metropolitan Council standards
Most recent sample: 2025-07-29
Monitoring stations: 2