Lower Sunshine Reservoir
Park County, Wyoming1,049 acresView mapDirections
Clarity, phosphorus, and algae sit in the clean band for this region.
↓ down from A at the last regrade
- Mesotrophic
- #2 of 5 in the county
- 162 ft max depth
- Public access
- Limited data
Lower Sunshine Reservoir in Park County, Wyoming has a water quality grade of B (Good). Water clarity: 10.6 ft visibility. Phosphorus: 10 µg/L. Surface area: 1049 acres.
- Clarity
- 10.6 ft
- Max depth
- ~162 ft est.
- Area
- 1,049 acres
- Type
- Mesotrophic
- Phosphorus
- 10 µg/L
- Public access
- Yes
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Watch Lower Sunshine Reservoir’s letter
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Lower Sunshine Reservoir is a 1,049-acre mesotrophic lake in Park County, Wyoming with an estimated average depth of about 162 feet. Water quality is graded B based on 1 sampling years through 2021. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 4 other monitored lakes in Park County, Lower Sunshine Reservoir ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, Wyoming DEQ, last sampled 2021-07-20. Grade methodology: LakeQuality methodology.
What Lower Sunshine Reservoir is good for
From access and monitoring records, not editorial picks.
- Clear water10.6 ft of visibility
- Boat launch1 documented ramp
- Big water1,049 acres
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)
Good clarity, visible to about 10.6 ft. Phosphorus 10 µg/L. TSI 40. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 10.6 ft | Not graded |
| Phosphorus | 10 µg/L | Good |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 40 | Mesotrophic |
Moderate nutrients, good water quality
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~162 ft est. |
| Average Depth | ~82 ft est. |
| Surface Area | 1,049 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 Lower Sunshine Reservoir.
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
- Sunshine Reservoir, LowerPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Lower Sunshine Reservoir
Reservoir Info (USACE NID)
Lower Sunshine Reservoir is a man-made reservoir impounded by the Lower Sunshine (completed 1972), built primarily for irrigation on the Sunshine Creek Offstream; earth-type dam, 162 ft tall and 1,660 ft long.
- Surface area
- 1,049 ac
- Normal storage
- 58,748 ac-ft
- Max storage
- 71,800 ac-ft
- Drainage area
- 26.5 sq mi
- Hazard class
- High
- Owner
- GREYBULL VALLEY IRRIGATION DISTRICT
All listed purposes: Irrigation;Fire Protection, Stock, Or Small Fish Pond;Hydroelectric.
Source: USACE National Inventory of Dams, NID ID WY01096 · Operator website
County Ranking
Ranked #2 of 5 lakes in Park County
Nearby Lakes in Park County
Frequently asked questions about Lower Sunshine Reservoir
Where is Lower Sunshine Reservoir?
- Lower Sunshine Reservoir is a lake in Park County, Wyoming. LakeQuality grades it B for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Lower Sunshine Reservoir?
- Lower Sunshine Reservoir in Park County, Wyoming has a water quality grade of B (Good). Water clarity: 10.6 ft visibility. Phosphorus: 10 µg/L. Surface area: 1049 acres.
Is Lower Sunshine Reservoir safe to swim in?
- The B is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
How deep is Lower Sunshine Reservoir?
- No published bathymetric survey covers Lower Sunshine Reservoir, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 162 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 1049 acres.
Are there boat ramps on Lower Sunshine Reservoir?
- Lower Sunshine Reservoir has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Sunshine Reservoir, Lower. Public access is listed as yes.
Explore Lower Sunshine Reservoir across LakeQuality
More Wyoming Lake Rankings
Other Grade B Lakes in Wyoming
Mesotrophic Lakes in Wyoming
Where this data comes from
8 measurements from 2 monitoring stations, 2021. 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_WATERSHED8 samples · 2021
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)
Named boat-access points from the USGS National Boat Ramps inventory