Mark Twain Lake
Ralls County, WisconsinEutrophic
Mark Twain Lake is a 5,900-acre productive, nutrient-rich eutrophic lake in Ralls County, MO. Water quality is graded D based on 3 sampling years through 2020. Compared to the 3 other monitored lakes in Ralls County, Mark Twain Lake ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, local state DNR records, last sampled 2020-09-19. Grade methodology: LakeGrade methodology.
Swimming Safety
Swimming not recommended, poor water quality with high algae risk
Water Quality Grade: D, Poor
Very murky, less than 2.5 ft of visibility. Phosphorus level: 60.8 µg/L. Chlorophyll-a: 18.3 µg/L. Trophic State Index: 62.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.5 ft | F |
| Phosphorus | 60.8 µg/L | D |
| Chlorophyll-a (Algae) | 18.3 µg/L | C |
| Trophic State Index (TSI) | 62 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 5.9K acres |
Location
County Ranking
Ranked #3 of 4 lakes in Ralls County
Cleaner Lakes Within 30 Miles
Mark Twain Lake holds Grade D. 4 nearby lakes hold higher grades.
- CMark Twain Lake by Hwy JRalls County · 0.1 mi · Higher grade (D → C)
- CMark Twain Lake Indian Creek ArmRalls County · 2.8 mi · Higher grade (D → C)
- CMark Twain LakeMonroe County · 6.5 mi · Higher grade (D → C)
- DHunnewell LakeShelby County · 17.1 mi · Higher overall water quality score
Nearby Lakes in Ralls County
More Wisconsin Lake Rankings
Other Grade D Lakes in Wisconsin
St. Louis city County · Clarity: 2.3 ft
Shelby County · Clarity: 3.2 ft
Macon County · Clarity: 1.8 ft
Harrison County · Clarity: 1.7 ft
Stone County · Clarity: 2.3 ft
Knox County · Clarity: 2.1 ft
Eutrophic Lakes in Wisconsin
Reservoir Info (USACE NID)
Mark Twain Lake is a man-made reservoir impounded by the Clarence Cannon Dam (completed 1983), built primarily for flood risk reduction on the SALT RIVER; concrete-type dam, 188 ft tall and 1,940 ft long.
- Surface area
- 5,900 ac
- Normal storage
- 520,661 ac-ft
- Max storage
- 1,862,000 ac-ft
- Drainage area
- 2,318 sq mi
- Hazard class
- High
- Owner
- USACE - St. Louis District
All listed purposes: Flood Risk Reduction;Navigation;Fish and Wildlife Pond;Recreation;Hydroelectric;Water Supply.
Source: USACE National Inventory of Dams, NID ID MO82201 · Operator website
Data Sources
Water quality data from the EPA Water Quality Portal
Grading methodology based on Metropolitan Council standards
Most recent sample: 2020-09-19
Monitoring stations: 1