City Reservoir
Park County, Wyoming12 acresView mapDirections
Nutrients and algae sit mid-range for this region.
↑ up from D at the last regrade
- Eutrophic
- #5 of 5 in the county
- Limited data
City Reservoir in Park County, Wyoming has a water quality grade of C (Fair). Phosphorus: 65 µg/L. Surface area: 12 acres.
- Area
- 12 acres
- Type
- Eutrophic
- Phosphorus
- 65 µg/L
- Trend
- ↑ Improving
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Watch City Reservoir’s letter
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City Reservoir is a 12-acre productive, nutrient-rich eutrophic lake in Park County, Wyoming. Water quality is graded C based on 1 sampling years through 2016. Overall water quality is improving over recent sampling years. Compared to the 4 other monitored lakes in Park County, City Reservoir ranks #5 for water quality.
Source: EPA Water Quality Portal sampling records, Wyoming DEQ, last sampled 2016-09-20. Grade methodology: LakeQuality methodology.
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 C is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Water Quality Grade: C (Fair)
No clarity data. Phosphorus 65 µg/L. TSI 64. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | 65 µg/L | Fair |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 64 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 12 acres |
No bathymetric survey has been published for City Reservoir, so its depth is not documented here.
Fishing City Reservoir
Water Quality Trend: ↑ Improving
Based on 3 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Phosphorus | ↑ Improving | -25 µg/L/yr | 3 |
Reservoir Info (USACE NID)
City Reservoir is a man-made reservoir impounded by the Markham (completed 1929), built primarily for water supply on the S Fork Shoshone Offstream; earth-type dam, 11 ft tall and 2,500 ft long.
- Surface area
- 12 ac
- Normal storage
- 67 ac-ft
- Max storage
- 730 ac-ft
- Drainage area
- 0.1 sq mi
- Hazard class
- Significant
- Owner
- CITY OF CODY
All listed purposes: Water Supply;Irrigation.
Source: USACE National Inventory of Dams, NID ID WY01101 · Operator website · Matched by proximity (0.24 km)
County Ranking
Ranked #5 of 5 lakes in Park County
Nearby Lakes in Park County
Frequently asked questions about City Reservoir
Where is City Reservoir?
- City Reservoir is a lake in Park County, Wyoming. LakeQuality grades it C for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for City Reservoir?
- City Reservoir in Park County, Wyoming has a water quality grade of C (Fair). Phosphorus: 65 µg/L. Surface area: 12 acres.
Is City Reservoir safe to swim in?
- The C is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Explore City Reservoir across LakeQuality
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Where this data comes from
6 measurements from 1 monitoring station, 2015–2016. 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 · 2015–2016
Analytical methods
- 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.