Half Moon Lake
Sublette County, WyomingView mapDirections
Wyoming DEQ publishes the water-quality measurements for Half Moon Lake. Here is what has been measured.
- Oligotrophic
- 111 ft max depth
- Public access
- Limited data
Half Moon Lake in Sublette County, Wyoming has water-quality measurements published by Wyoming DEQ, shown here as reported. Water clarity: 22.2 ft visibility. Phosphorus: 10 µg/L.
Half Moon Lake is a cold, clear oligotrophic lake in Sublette County, Wyoming with an estimated average depth of about 111 feet. 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. Methodology: how these readings are compared.
If you are planning to stay, you can search lake houses and cabins around Half Moon Lake on Vrbo, or look for a hotel room near the lake on Booking.com or Expedia.
What Half Moon Lake is good for
From access and monitoring records, not editorial picks.
- Clear water22.2 ft of visibility
Swimming conditions
Readings onlyLimited data
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Half Moon Lake is safe to swim in today is a call for the Wyoming Department of Environmental Quality and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Half Moon Lake
These are the measurements Wyoming DEQ publishes for Half Moon Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Crystal clear, you can see 22.2 ft down. Phosphorus 10 µg/L. TSI 35.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 22.2ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 10µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | No reading The green pigment in algae — a direct measure of how much algae is in the water. | |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 35 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about Half Moon Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Max depth
~111 ft est.
Public access
Yes
Listed by Wyoming DEQ
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
Watershed (drainage) area
81 sq mi
HydroLAKES / HydroSHEDS
Surface area
983 acres
HydroLAKES / HydroSHEDS
Shoreline
8.6 mi
HydroLAKES / HydroSHEDS
Elevation
7,612 ft
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.
Stays via Stay22
Stays near Half Moon Lake
Compare lakeside cabins, hotels, and vacation rentals near Half Moon Lake in Sublette County, Wyoming — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
Top-rated places to stay near Half Moon Lake
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Fishing Half Moon Lake
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. Its water-quality measurements are published by Wyoming DEQ and shown on this page as reported.
What is the water quality of Half Moon Lake?
- Half Moon Lake in Sublette County, Wyoming has water-quality measurements published by Wyoming DEQ, shown here as reported. Water clarity: 22.2 ft visibility. Phosphorus: 10 µg/L.
Is Half Moon Lake safe to swim in?
- Nutrient and algae readings are 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.
Can I fish at Half Moon Lake?
- Public access to Half Moon Lake is listed as yes on the lake record. Seasons, size and bag limits, and whether you need a license are set by Wyoming's fish and wildlife agency, so check its current regulations before you go.
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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)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.
Other records on this page
Lake size & watershed from HydroLAKES (HydroSHEDS)