Sibley Lake
Sheridan County, Wyoming34 acresView mapDirections
Clarity, phosphorus, and algae sit in the clean band for this region.
- Mesotrophic
- #1 of 5 in the county
- 13 ft max depth
- Public access
- Limited data
Sibley Lake in Sheridan County, Wyoming has a water quality grade of B (Good). Water clarity: 9.2 ft visibility. Phosphorus: 10 µg/L. Surface area: 34 acres.
- Clarity
- 9.2 ft
- Max depth
- ~13 ft est.
- Area
- 34 acres
- Type
- Mesotrophic
- Phosphorus
- 10 µg/L
- Public access
- Yes
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Watch Sibley Lake’s letter
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Sibley Lake is a 34-acre mesotrophic lake in Sheridan County, Wyoming with an estimated average depth of about 13 feet. Water quality is graded B based on 1 sampling years through 2019. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 4 other monitored lakes in Sheridan County, Sibley Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Wyoming DEQ, last sampled 2019-09-10. Grade methodology: LakeQuality methodology.
What Sibley Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
- Camping3 public campgrounds 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)
Moderate clarity, visible to about 9.2 ft. Phosphorus 10 µg/L. TSI 41. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 9.2 ft | Not graded |
| Phosphorus | 10 µg/L | Good |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 41 | Mesotrophic |
Moderate nutrients, good water quality
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~13 ft est. |
| Surface Area | 34 acres |
| 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 Sibley 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
- Sibley LakePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Public campgrounds near Sibley Lake
- Sibley Lake0.3 km
- Prune Creek2.7 km
- Pine Island3.7 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 Sibley Lake
Reservoir Info (USACE NID)
Sibley Lake is a man-made reservoir impounded by the Sibley (completed 1938), built primarily for recreation on the Prune Creek; earth-type dam, 35 ft tall and 420 ft long.
- Surface area
- 34 ac
- Normal storage
- 379 ac-ft
- Max storage
- 635 ac-ft
- Drainage area
- 5 sq mi
- Hazard class
- High
- Owner
- USDA FS
All listed purposes: Recreation;Fish and Wildlife Pond.
Source: USACE National Inventory of Dams, NID ID WY01344 · Operator website
County Ranking
Ranked #1 of 5 lakes in Sheridan County
Nearby Lakes in Sheridan County
Frequently asked questions about Sibley Lake
Where is Sibley Lake?
- Sibley Lake is a lake in Sheridan County, Wyoming. LakeQuality grades it B for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Sibley Lake?
- Sibley Lake in Sheridan County, Wyoming has a water quality grade of B (Good). Water clarity: 9.2 ft visibility. Phosphorus: 10 µg/L. Surface area: 34 acres.
Is Sibley Lake safe to swim in?
- The B is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
How deep is Sibley Lake?
- No published bathymetric survey covers Sibley Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 13 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 34 acres.
Are there boat ramps on Sibley Lake?
- Sibley Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Sibley Lake. Public access is listed as yes.
Are there campgrounds on Sibley Lake?
- Sibley Lake has 3 public campgrounds from USGS The National Map within 5 km, including Sibley Lake, Prune Creek, Pine Island. 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 Sibley Lake across LakeQuality
14.9 mi away · 120 ft
Species activity outlook by water temperature and season
Where to stay at Wyoming's top lakes, each with its grade
Moderate nutrients, good water quality
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Where this data comes from
6 measurements from 1 monitoring station, 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_WATERSHED6 samples · 2019
Analytical methods
- Secchi
- Total Phosphorus After Block Digestion
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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Named boat-access points from the USGS National Boat Ramps inventory
Public campgrounds from USGS The National Map Structures, within about 3 miles