Keyhole Reservoir
Crook County, Wyoming9,411 acresView mapDirections
Wyoming DEQ publishes the water-quality measurements for Keyhole Reservoir. Here is what has been measured.
- Mesotrophic
- Public access
- Limited data
Keyhole Reservoir in Crook County, Wyoming has water-quality measurements published by Wyoming DEQ, shown here as reported. Water clarity: 7.7 ft visibility. Phosphorus: 20 µg/L. Surface area: 9411 acres.
Keyhole Reservoir is a 9,411-acre mesotrophic lake in Crook County, Wyoming. Limited fish-species data available. Public access is available with 2 public boat landings. Compared to the 2 other monitored lakes in Crook County, Keyhole Reservoir ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Wyoming DEQ, last sampled 2018-09-10. Methodology: how these readings are compared.
At about 9,400 acres, Keyhole Reservoir is large enough that where you stay decides which shore you see most of. It has 2 public boat landings, so a lakefront rental is not the only way to get a boat on the water. Vrbo is where to look for cabins and lake homes around Keyhole Reservoir, and Booking.com and Expedia search hotels near the lake for your dates.
What Keyhole Reservoir is good for
From access and monitoring records, not editorial picks.
- Boat launch2 documented ramps
- Big water9,411 acres
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 Keyhole Reservoir 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 Keyhole Reservoir
These are the measurements Wyoming DEQ publishes for Keyhole Reservoir, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Moderate clarity, visible to about 7.7 ft. Phosphorus 20 µg/L. TSI 48.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 7.7ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 20µg/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. | 48 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Keyhole Reservoir
Answers come straight from the public measurements and survey records on this page.
Lake Details
Surface area
9,411 acres
Public access
Yes
Listed by Wyoming DEQ
No bathymetric survey has been published for Keyhole Reservoir, so its depth is not documented here.
Recreation & Access
- Keyhole State PArkPublic
- Keyhole MarinaSemi-private
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Keyhole Reservoir
Compare lakeside cabins, hotels, and vacation rentals near Keyhole Reservoir in Crook 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 Keyhole Reservoir
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Fishing Keyhole Reservoir
Water quality readings over time
2 seasons of samples on record (2017–2018). Calling a direction takes at least 4 years of the same measurement.
Phosphorus
Stable0 µg/L/yr2 years
Reservoir Info (USACE NID)
Keyhole Reservoir is a man-made reservoir impounded by the Keyhole Dam (completed 1952), built primarily for flood risk reduction on the Belle Fourche River; earth-type dam, 168 ft tall and 3,420 ft long.
- Surface area
- 9,411 ac
- Normal storage
- 334,215 ac-ft
- Max storage
- 629,025 ac-ft
- Drainage area
- 1,949.73 sq mi
- Hazard class
- High
- Owner
- BUREAU OF RECLAMATION
All listed purposes: Flood Risk Reduction;Irrigation.
Source: USACE National Inventory of Dams, NID ID WY01380 · Operator website
Nearby Lakes in Crook County
Frequently asked questions about Keyhole Reservoir
Where is Keyhole Reservoir?
- Keyhole Reservoir is a lake in Crook County, Wyoming. Its water-quality measurements are published by Wyoming DEQ and shown on this page as reported.
What is the water quality of Keyhole Reservoir?
- Keyhole Reservoir in Crook County, Wyoming has water-quality measurements published by Wyoming DEQ, shown here as reported. Water clarity: 7.7 ft visibility. Phosphorus: 20 µg/L. Surface area: 9411 acres.
Is Keyhole Reservoir safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Are there boat ramps on Keyhole Reservoir?
- Keyhole Reservoir has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Keyhole State PArk, Keyhole Marina. Public access is listed as yes.
Can I fish at Keyhole Reservoir?
- Keyhole Reservoir has 2 documented boat landings in the USGS National Boat Ramps inventory. 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.
Explore Keyhole Reservoir across LakeQuality
Depth, room, public access, and the state wake-sport rules
Species activity outlook by water temperature and season
Where to stay at Wyoming's top lakes, each with its readings
Wyoming's cleanest lakes, ranked on agency measurements
Planning a trip around Devils Tower?
Keyhole Reservoir is about 15 miles from Devils Tower National Monument. Crowds there swing hard by season, so the month you pick changes both how busy the park is and what lodging costs.
Best time to visit Devils Tower →More lakes in Wyoming
Other Lakes in Wyoming
Mesotrophic Lakes in Wyoming
Where this data comes from
9 measurements from 1 monitoring station, 2017–2018. 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_WATERSHED9 samples · 2017–2018
Analytical methods
- Secchi
- Total Phosphorus After Block Digestion
Monitoring station identifiers (1)
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
Named boat-access points from the USGS National Boat Ramps inventory