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C
Phelps County, Missouri

Little Prairie Lake

Grade CFair · 8.6 ft clarity

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Eutrophic

Little Prairie Lake is a 100-acre productive, nutrient-rich eutrophic lake in Phelps County, Missouri. Water quality is graded C based on 3 sampling years through 2021. Water clarity is declining over recent sampling years. Compared to the 2 other monitored lakes in Phelps County, Little Prairie Lake ranks #2 for water quality.

Source: EPA Water Quality Portal sampling records, Missouri DNR, last sampled 2021-09-07. Grade methodology: LakeGrade methodology.

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Swimming Safety

Generally safe for swimming, moderate water quality

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Water Quality Grade: C, Fair

Moderate clarity, visible to about 8.6 ft. Phosphorus level: 54 µg/L. Chlorophyll-a: 8.9 µg/L. Trophic State Index: 53.

MetricValueGrade
Water Clarity (Secchi Depth)8.6 ftC
Phosphorus54 µg/LC
Chlorophyll-a (Algae)8.9 µg/LB
Trophic State Index (TSI)53Eutrophic

High nutrients, frequent algae, reduced clarity

Lake Details

CharacteristicValue
Surface Area100 acres

Where to stay near Little Prairie Lake

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Fishing Little Prairie Lake

Water Quality Trend: Stable

Based on 5 years of monitoring data (2020-2025).

MetricTrendChange/YearYears
Water Clarity Declining-0.303 m/yr4
Phosphorus Stable-0.19 µg/L/yr5
Chlorophyll-a Improving-2.03 µg/L/yr5
See year-by-year chart →

Water Temperature

Little Prairie Lake averages about 83°F at the surface in summer, usually warmest in Jul (about 86°F) and coldest in Jun (about 82°F). These are typical values by month — not a live reading.

Jan
Feb
Mar
Apr
May
Jun
82°
Jul
86°
Aug
82°
Sep
Oct
Nov
Dec

Typical surface water temperature by month, from 10 field readings (20162021) via the EPA Water Quality Portal.

Location

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County Ranking

Ranked #2 of 3 lakes in Phelps County

Nearby Lakes in Phelps County

More records, surveys & data sources

Reservoir Info (USACE NID)

Little Prairie Lake is a man-made reservoir impounded by the William E. Towell Dam (completed 1965), built primarily for recreation on the TRIBUTARY OF BOUBEUSE RIVER; earth-type dam, 48 ft tall and 1,450 ft long.

Surface area
100 ac
Normal storage
1,300 ac-ft
Max storage
2,490 ac-ft
Drainage area
2.41 sq mi
Hazard class
High
Owner
MO DEPT OF CONSERVATION

Source: USACE National Inventory of Dams, NID ID MO30090 · Operator website · Matched by proximity (0.39 km)

EPA Impairment Status

Little Prairie Lake is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 5).

Causes of impairment

Mercury

Source: EPA ATTAINS assessment unit MO_7287.00 · Official waterbody report · Matched by proximity (0.24 km)

Lake Size & Watershed

Watershed (drainage) area
3 sq mi
Mean depth (est.)
13.1 ft
Shoreline
2.1 mi
Elevation
1,030 ft

Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.

Regulated Pollution Sources Nearby

10 EPA-permitted facilities operate within about 5 miles of Little Prairie Lake under Clean Water Act (NPDES) discharge permits. 3 facilities have a reported Clean Water Act violation in the past three years.

  • Glado Wastewater Treatment Facility
    Rolla · 1.5 mi away · NPDES MO0084191
    Recent violation
  • Formerly Little Dixie Truck Port Wwtf
    Rolla · 1.7 mi away · NPDES MO0104493
    Recent violation
  • Country Valley Home
    St. James · 2.7 mi away · NPDES MO0088064
    Recent violation
  • Brewer Science, Inc
    Rolla · 1.6 mi away · NPDES MONX00017
  • Brewer Science, Inc. - Building 3A/8
    Rolla · 1.7 mi away · NPDES MONX00995
  • Mo-Sci Corporation
    Rolla · 1.7 mi away · NPDES MONX00306

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: 2021-09-07

Monitoring stations: 1

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