Mark Twain Lake is a productive, nutrient-rich eutrophic lake in Monroe County, Missouri. Water quality is graded F based on 3 sampling years through 2021. Limited fish-species data available. Public access is available with 2 public boat landings. Compared to the 2 other monitored lakes in Monroe County, Mark Twain Lake ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, Missouri DNR, last sampled 2021-08-03. Grade methodology: LakeGrade methodology.
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Swimming Safety
Avoid swimming, very poor water quality, potential algae toxins
Water Quality Grade: F, Very Poor
Very murky, less than 2.5 ft of visibility. Phosphorus level: 80 µg/L. Chlorophyll-a: 92.6 µg/L. Trophic State Index: 69.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.5 ft | F |
| Phosphorus | 80 µg/L | D |
| Chlorophyll-a (Algae) | 92.6 µg/L | F |
| Trophic State Index (TSI) | 69 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Mark Twain Lake
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Fishing Mark Twain Lake
Recreation & Access
Location
County Ranking
Ranked #3 of 3 lakes in Monroe County
Cleaner Lakes Within 30 Miles
Mark Twain Lake holds Grade F. 5 nearby lakes hold higher grades.
- AOasis Ranch LakeAudrain County · 17 mi · Two grade letters higher (F → A)
- AOasis Ranch Upper LakeAudrain County · 17.1 mi · Two grade letters higher (F → A)
- CMark Twain LakeMonroe County · 4.8 mi · Two grade letters higher (F → C)
- CMark Twain Lake Indian Creek ArmRalls County · 9.1 mi · Two grade letters higher (F → C)
- CMark Twain Lake by Hwy JRalls County · 10.5 mi · Two grade letters higher (F → C)
Nearby Lakes in Monroe County
Explore Mark Twain Lake across LakeGrade
More Missouri Lake Rankings
Other Grade F Lakes in Missouri
Eutrophic Lakes in Missouri
More records, surveys & data sources
EPA Impairment Status
Mark Twain Lake 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_7033.00 · Official waterbody report
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grading methodology based on Metropolitan Council standards
Public boat-access points from the USGS National Boat Ramps inventory
Most recent sample: 2021-08-03
Monitoring stations: 1