Cap Mauzy Lake
Union County, Kentucky83 acresView mapDirections
Clarity, phosphorus, and algae sit in the clean band for this region.
↑ up from C at the last regrade
- Eutrophic
- Impaired · Nutrients (phosphorus, nitrogen)
- #2 of 2 in the county
- 40 ft max depth
- Public access
Cap Mauzy Lake in Union County, Kentucky has a water quality grade of B (Good). Phosphorus: 30 µg/L. Surface area: 83.2 acres.
- Max depth
- ~40 ft est.
- Area
- 83 acres
- Type
- Eutrophic
- Phosphorus
- 30 µg/L
- Trend
- ↓ Declining
- Public access
- Yes
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Cap Mauzy Lake is a 83-acre productive, nutrient-rich eutrophic lake in Union County, Kentucky with an estimated average depth of about 40 feet. Water quality is graded B based on 1 sampling years through 2021. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available. Compared to the 1 other monitored lakes in Union County, Cap Mauzy Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, KY DOW, last sampled 2021-09-16. Grade methodology: LakeQuality methodology.
Swimming Safety
Grade onlyLow algae
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 B is nutrients and algae, not a swimming clearance. Cap Mauzy Lake is listed impaired under Clean Water Act §303(d) (IR 5) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Water Quality Grade: B (Good)
No clarity data. Phosphorus 30 µg/L. TSI 53. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | 30 µg/L | Good |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 53 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~40 ft est. |
| Average Depth | ~11 ft est. |
| Surface Area | 83 acres |
| Public Access | Yes |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Kentucky has not published bathymetry for Cap Mauzy Lake.
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Fishing Cap Mauzy Lake
Water Quality Trend: ↓ Declining
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Phosphorus | ↓ Declining | +2.64 µg/L/yr | 2 |
Reservoir Info (USACE NID)
Cap Mauzy Lake is a man-made reservoir impounded by the Des Islet Dam (completed 1945), built primarily for recreation on the Highland Creek; earth-type dam, 32 ft tall and 900 ft long.
- Surface area
- 83.2 ac
- Normal storage
- 670.9 ac-ft
- Max storage
- 1,300 ac-ft
- Drainage area
- 1.08 sq mi
- Hazard class
- Significant
- Owner
- COMMONWEALTH OF KENTUCKY
Source: USACE National Inventory of Dams, NID ID KY00001 · Operator website · Matched by proximity (0.37 km)
EPA Impairment Status
Cap Mauzy Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit KY-434 · Official waterbody report
County Ranking
Ranked #2 of 2 lakes in Union County
Nearby Lakes in Union County
Frequently asked questions about Cap Mauzy Lake
Where is Cap Mauzy Lake?
- Cap Mauzy Lake is a lake in Union County, Kentucky. LakeQuality grades it B for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Cap Mauzy Lake?
- Cap Mauzy Lake in Union County, Kentucky has a water quality grade of B (Good). Phosphorus: 30 µg/L. Surface area: 83.2 acres.
Is Cap Mauzy Lake safe to swim in?
- The B is nutrients and algae, not a swimming clearance. Cap Mauzy Lake is listed impaired under Clean Water Act §303(d) (IR 5) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
How deep is Cap Mauzy Lake?
- No published bathymetric survey covers Cap Mauzy Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 40 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate. The lake covers 83.2 acres.
Explore Cap Mauzy Lake across LakeQuality
More Kentucky Lake Rankings
Other Grade B Lakes in Kentucky
Eutrophic Lakes in Kentucky
Where this data comes from
18 measurements from 2 monitoring stations, 2016–2021. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- KY WQX
21KY_WQX18 samples · 2016–2021
Analytical methods
- Phosphorus by Colorimetry
- Total Phosphorus After Block Digestion
- Turbidity by Nephelometry
Monitoring station identifiers (2)
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
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)