Half Moon Lake
Sublette County, WyomingView mapDirections
Clarity, phosphorus, and algae sit in the clean band for this region.
↓ down from A at the last regrade
- Oligotrophic
- #3 of 8 in the county
- 111 ft max depth
- Public access
- Limited data
Half Moon Lake in Sublette County, Wyoming has a water quality grade of B (Good). Water clarity: 22.2 ft visibility. Phosphorus: 10 µg/L.
- Clarity
- 22.2 ft
- Max depth
- ~111 ft est.
- Type
- Oligotrophic
- Phosphorus
- 10 µg/L
- Public access
- Yes
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Half Moon Lake is a cold, clear oligotrophic lake in Sublette County, Wyoming with an estimated average depth of about 111 feet. Water quality is graded B based on 1 sampling years through 2019. Limited fish-species data available. Public access is available. Compared to the 7 other monitored lakes in Sublette County, Half Moon Lake ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, Wyoming DEQ, last sampled 2019-09-26. Grade methodology: LakeQuality methodology.
What Half Moon Lake is good for
From access and monitoring records, not editorial picks.
- Clear water22.2 ft of visibility
- Camping1 public campground nearby
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 B is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Water Quality Grade: B (Good)
Crystal clear, you can see 22.2 ft down. Phosphorus 10 µg/L. TSI 35. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 22.2 ft | Not graded |
| Phosphorus | 10 µg/L | Good |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 35 | Oligotrophic |
Low nutrients, clear water. The letter is not a swimming clearance.
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~111 ft est. |
| Average Depth | ~61 ft est. |
| Public Access | Yes |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Wyoming has not published bathymetry for Half Moon 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.
Recreation & Access
Public campgrounds near Half Moon Lake
- Half Moon Lake Campground2.7 km
Nearest public campgrounds in the USGS National Map inventory, within about 3 miles. An empty list means USGS records no campground that close, which is not the same as camping being unavailable. Where the source gives an official reservation link, it is used; the cabin and hotel search does not cover campsites. More camping lakes
Fishing Half Moon Lake
County Ranking
Ranked #3 of 8 lakes in Sublette County
Nearby Lakes in Sublette County
Frequently asked questions about Half Moon Lake
Where is Half Moon Lake?
- Half Moon Lake is a lake in Sublette County, Wyoming. LakeQuality grades it B for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Half Moon Lake?
- Half Moon Lake in Sublette County, Wyoming has a water quality grade of B (Good). Water clarity: 22.2 ft visibility. Phosphorus: 10 µg/L.
Is Half Moon Lake safe to swim in?
- The B is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
How deep is Half Moon Lake?
- No published bathymetric survey covers Half Moon Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 111 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
Are there campgrounds on Half Moon Lake?
- Half Moon Lake has 1 public campground from USGS The National Map within 5 km, including Half Moon Lake Campground. This is a location join, not a booking. Cabins and hotels are listed separately; campsite reservations use the official link when the source provides one.
Explore Half Moon Lake across LakeQuality
13.5 mi away · recorded at 102°F
Species activity outlook by water temperature and season
Where to stay at Wyoming's top lakes, each with its grade
Low nutrients, clear water. The letter is not a swimming clearance.
Wyoming's cleanest and most-polluted lakes, ranked
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Other Grade B Lakes in Wyoming
Oligotrophic Lakes in Wyoming
Where this data comes from
12 measurements from 2 monitoring stations, 2019. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- State of Wyoming Department of Environmental Quality Watershed Program
WYDEQ_WATERSHED12 samples · 2019
Analytical methods
- Secchi
- Total Phosphorus After Block Digestion
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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Public campgrounds from USGS The National Map Structures, within about 3 miles