Oasis Ranch Upper Lake
Audrain County, MissouriView mapDirections
Clarity, phosphorus, and algae all sit in the cleanest band for this region.
- Oligotrophic
- #1 of 3 in the county
- Limited data
Oasis Ranch Upper Lake in Audrain County, Missouri has a water quality grade of A (Excellent). Water clarity: 14.4 ft visibility. Phosphorus: 12 µg/L. Chlorophyll-a (algae): 1.8 µg/L.
- Clarity
- 14.4 ft
- Type
- Oligotrophic
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Watch Oasis Ranch Upper Lake’s letter
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Oasis Ranch Upper Lake is a cold, clear oligotrophic lake in Audrain County, Missouri. Water quality is graded A based on 2 sampling years through 2024. Compared to the 2 other monitored lakes in Audrain County, Oasis Ranch Upper Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Missouri DNR, last sampled 2024-09-18. Grade methodology: LakeQuality methodology.
What Oasis Ranch Upper Lake is good for
From access and monitoring records, not editorial picks.
- Clear water14.4 ft of visibility
Swimming Safety
Grade onlyLimited data
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
The A is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Water Quality Grade: A (Excellent)
Good clarity, visible to about 14.4 ft. Phosphorus 12 µg/L. Chlorophyll-a 1.8 µg/L. TSI 38. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 14.4 ft | Not graded |
| Phosphorus | 12 µg/L | Good |
| Chlorophyll-a (Algae) | 1.8 µg/L | Good |
| Trophic State Index (TSI) | 38 | Oligotrophic |
Low nutrients, clear water. The letter is not a swimming clearance.
Fishing Oasis Ranch Upper Lake
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Oasis Ranch Upper Lake under Clean Water Act (NPDES) discharge permits.
- Monroe County Pwsd 2 - Rush Hill WwtfRush Hill · 2.9 mi away · NPDES MO0126888
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.
County Ranking
Ranked #1 of 3 lakes in Audrain County
Nearby Lakes in Audrain County
Frequently asked questions about Oasis Ranch Upper Lake
Where is Oasis Ranch Upper Lake?
- Oasis Ranch Upper Lake is a lake in Audrain County, Missouri. LakeQuality grades it A for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Oasis Ranch Upper Lake?
- Oasis Ranch Upper Lake in Audrain County, Missouri has a water quality grade of A (Excellent). Water clarity: 14.4 ft visibility. Phosphorus: 12 µg/L. Chlorophyll-a (algae): 1.8 µg/L.
Is Oasis Ranch Upper Lake safe to swim in?
- The A is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Explore Oasis Ranch Upper Lake across LakeQuality
Species activity outlook by water temperature and season
Where to stay at Missouri's top lakes, each with its grade
Low nutrients, clear water. The letter is not a swimming clearance.
Missouri's cleanest and most-polluted lakes, ranked
More Missouri Lake Rankings
Other Grade A Lakes in Missouri
Oligotrophic Lakes in Missouri
Where this data comes from
17 measurements from 1 monitoring station, 2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Univ. of Missouri, Columbia
UMC17 samples · 2024
Analytical methods
- Depth, Secchi disk in meters
- 4500 P E ~ Phosphorus in Water by Colorimetry- Ascorbic Acid Method
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
Monitoring station identifiers (1)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Other records on this page
Regulated discharger data from EPA ECHO (ICIS-NPDES)