1
AOasis Ranch Lake
Audrain County, Wisconsin · 20.6 mi from Mark Twain Lake
- +Two grade letters higher (C → A)
- ++10.3 ft water clarity
- +Lower phosphorus (8 vs 36 µg/L)
Cleaner Lakes Than Mark Twain Lake
1 higher-graded lake within 30 miles, ranked by grade improvement and proximity.
Mark Twain Lake carries a Grade C (Fair) water quality score. Within 30 miles, 1 lake holds a higher grade. Oasis Ranch Lake (Audrain County, Grade A, 20.6 mi away) is the closest meaningful upgrade.
How this list is built
Every lake on LakeQuality has a calculated grade from EPA Water Quality Portal samples — secchi depth, total phosphorus, and chlorophyll-a measured against Metropolitan Council thresholds. To suggest cleaner alternatives, we filter lakes within 30 miles to those with a strictly higher numeric score, then rank by grade improvement with a small proximity tiebreak. Cross-state and limited-data lakes are excluded so the list stays locally relevant.