Johnson Reservoir
Sevier County, UtahView mapDirections
Utah DWQ publishes the water-quality measurements for Johnson Reservoir. Here is what has been measured.
- Eutrophic
- Impaired · Nutrients (phosphorus, nitrogen)
- 17 ft max depth
- Public access
- Limited data
Johnson Reservoir in Sevier County, Utah has water-quality measurements published by Utah DWQ, shown here as reported. Water clarity: 2 ft visibility. Phosphorus: 82 µg/L. Chlorophyll-a (algae): 29.1 µg/L.
Johnson Reservoir is a productive, nutrient-rich eutrophic lake in Sevier County, Utah with an estimated average depth of about 17 feet. Water clarity is declining over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 6 other monitored lakes in Sevier County, Johnson Reservoir ranks #5 for water quality.
Source: EPA Water Quality Portal sampling records, Utah DWQ, last sampled 2025-09-09. Methodology: how these readings are compared.
Johnson Reservoir has one public boat landing. Vrbo is where to look for cabins and lake homes around Johnson Reservoir, and Booking.com and Expedia search hotels near the lake for your dates.
What Johnson Reservoir is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
- Camping3 public campgrounds nearby
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. Johnson Reservoir is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether Johnson Reservoir is safe to swim in today is a call for the Utah Division of Water Quality and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Johnson Reservoir
These are the measurements Utah DWQ publishes for Johnson Reservoir, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Very murky, less than 2 ft of visibility. Phosphorus 82 µg/L. Chlorophyll-a 29.1 µg/L. TSI 66.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 2ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 82µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 29.1µg/L | Poor GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 66 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Johnson Reservoir
Answers come straight from the public measurements and survey records on this page.
Lake Details
Max depth
~17 ft est.
Public access
Yes
Listed by Utah DWQ
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Utah has not published bathymetry for Johnson Reservoir.
Lake Size & Watershed
Watershed (drainage) area
59 sq mi
HydroLAKES / HydroSHEDS
Surface area
635 acres
HydroLAKES / HydroSHEDS
Shoreline
4.6 mi
HydroLAKES / HydroSHEDS
Elevation
8,825 ft
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
- Johnson ReservoirPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Public campgrounds near Johnson Reservoir
- Paiute Campground1.8 km
- Tasha Equestrian Campground2.3 km
- Frying Pan Campground3.6 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
Stays via Stay22
Stays near Johnson Reservoir
Compare lakeside cabins, hotels, and vacation rentals near Johnson Reservoir in Sevier County, Utah — 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. The water-quality readings cover nutrients and algae, not lodging. Cabins and rentals around Johnson Reservoir are listed below.
Top-rated places to stay near Johnson Reservoir
Prices for Oct 30–Nov 1, 4 adults. Change dates on the map below.
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Fishing Johnson Reservoir
Water quality readings over time
3 seasons of samples on record (2013–2025). Calling a direction takes at least 4 years of the same measurement.
Water clarity
Worsening3 years
Chlorophyll-a
Improving-30.93 µg/L/yr2 years
Reservoir Info (USACE NID)
Johnson Reservoir is a man-made reservoir impounded by the Johnson (completed 1910), built primarily for irrigation on the Fremont River; earth-type dam, 31 ft tall and 448 ft long.
- Normal storage
- 10,380 ac-ft
- Max storage
- 14,770 ac-ft
- Drainage area
- 36 sq mi
- Hazard class
- High
- Owner
- FREMONT IRRIGATION COMPANY
Source: USACE National Inventory of Dams, NID ID UT00153 · Operator website
EPA Impairment Status
Johnson Reservoir is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
Designated uses not supporting: Aquatic life.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit UT-L-14070003-010_00 · Official waterbody report
Nearby Lakes in Sevier County
Frequently asked questions about Johnson Reservoir
Where is Johnson Reservoir?
- Johnson Reservoir is a lake in Sevier County, Utah. Its water-quality measurements are published by Utah DWQ and shown on this page as reported.
What is the water quality of Johnson Reservoir?
- Johnson Reservoir in Sevier County, Utah has water-quality measurements published by Utah DWQ, shown here as reported. Water clarity: 2 ft visibility. Phosphorus: 82 µg/L. Chlorophyll-a (algae): 29.1 µg/L.
Is Johnson Reservoir safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Johnson Reservoir is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
How deep is Johnson Reservoir?
- No published bathymetric survey covers Johnson Reservoir, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 17 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
Are there boat ramps on Johnson Reservoir?
- Johnson Reservoir has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Johnson Reservoir. Public access is listed as yes.
Can I fish at Johnson Reservoir?
- Johnson Reservoir has 1 documented boat landing in the USGS National Boat Ramps inventory. Seasons, size and bag limits, and whether you need a license are set by Utah's fish and wildlife agency, so check its current regulations before you go.
Are there campgrounds on Johnson Reservoir?
- Johnson Reservoir has 3 public campgrounds from USGS The National Map within 5 km, including Paiute Campground, Tasha Equestrian Campground, Frying Pan Campground. 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 Johnson Reservoir across LakeQuality
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Where this data comes from
24 measurements from 1 monitoring station, 2013–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Utah Department Of Environmental Quality
UTAHDWQ_WQX24 samples · 2013–2025
Analytical methods
- Field Measurements
- Phosphorus by Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
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
Impairment status from EPA ATTAINS 303(d) database
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