Muddy Guard Reservoir
Johnson County, Wyoming48 acresView mapDirections
Clarity, phosphorus, and algae sit in the clean band for this region.
- Oligotrophic
- #4 of 5 in the county
- Limited data
Muddy Guard Reservoir in Johnson County, Wyoming has a water quality grade of B (Good). Water clarity: 15.2 ft visibility. Phosphorus: 10 µg/L. Surface area: 48 acres.
- Clarity
- 15.2 ft
- Area
- 48 acres
- Type
- Oligotrophic
- Phosphorus
- 10 µg/L
- Trend
- ↑ Improving
Stays via Stay22
Stays near Muddy Guard Reservoir
Compare lakeside cabins, hotels, and vacation rentals near Muddy Guard Reservoir in Johnson 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 Muddy Guard Reservoir
Prices for Sep 11–13, 4 adults. Change dates on the map below.
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a whole trip? See where to stay at Wyoming’s top lakes →
Watch Muddy Guard Reservoir’s letter
Email me if this lake’s grade moves. Grades stay free.
Or email
Muddy Guard Reservoir is a 48-acre cold, clear oligotrophic lake in Johnson County, Wyoming. Water quality is graded B based on 1 sampling years through 2019. Overall water quality is improving over recent sampling years. Compared to the 4 other monitored lakes in Johnson County, Muddy Guard Reservoir ranks #4 for water quality.
Source: EPA Water Quality Portal sampling records, Wyoming DEQ, last sampled 2019-09-11. Grade methodology: LakeQuality methodology.
What Muddy Guard Reservoir is good for
From access and monitoring records, not editorial picks.
- Clear water15.2 ft of visibility
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)
Crystal clear, you can see 15.2 ft down. Phosphorus 10 µg/L. TSI 38. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 15.2 ft | Not graded |
| Phosphorus | 10 µg/L | Good |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 38 | Oligotrophic |
Low nutrients, clear water. The letter is not a swimming clearance.
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 48 acres |
No bathymetric survey has been published for Muddy Guard Reservoir, so its depth is not documented here.
Fishing Muddy Guard Reservoir
Water Quality Trend: ↑ Improving
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +1.24 m/yr | 2 |
| Phosphorus | ↑ Improving | -4 µg/L/yr | 2 |
Reservoir Info (USACE NID)
Muddy Guard Reservoir is a man-made reservoir impounded by the Muddy Guard No. 2 South Dam (completed 1976), built primarily for irrigation on the Erosion Draw & Guard Draw; earth-type dam, 57 ft tall and 1,600 ft long.
- Surface area
- 48 ac
- Normal storage
- 1,934 ac-ft
- Max storage
- 1,934 ac-ft
- Drainage area
- 0.4 sq mi
- Hazard class
- High
- Owner
- NORTH FORK IRRIGATION DISTRICT
All listed purposes: Irrigation;Fish and Wildlife Pond.
Source: USACE National Inventory of Dams, NID ID WY01771 · Operator website · Matched by proximity (0.8 km)
County Ranking
Ranked #4 of 5 lakes in Johnson County
Nearby Lakes in Johnson County
Frequently asked questions about Muddy Guard Reservoir
Where is Muddy Guard Reservoir?
- Muddy Guard Reservoir is a lake in Johnson County, Wyoming. LakeQuality grades it B for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Muddy Guard Reservoir?
- Muddy Guard Reservoir in Johnson County, Wyoming has a water quality grade of B (Good). Water clarity: 15.2 ft visibility. Phosphorus: 10 µg/L. Surface area: 48 acres.
Is Muddy Guard Reservoir safe to swim in?
- The B is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Explore Muddy Guard Reservoir across LakeQuality
Species activity outlook by water temperature and season
Where to stay at Wyoming's top lakes, each with its grade
Low nutrients, clear water. The letter is not a swimming clearance.
Wyoming's cleanest and most-polluted lakes, ranked
More Wyoming Lake Rankings
Other Grade B Lakes in Wyoming
Oligotrophic Lakes in Wyoming
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)
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.