Tropic Reservoir
Garfield County, UtahView mapDirections
Clarity, phosphorus, and algae all sit in the cleanest band for this region.
- Oligotrophic
- Impaired · pH / acidity
- #4 of 10 in the county
- 13 ft max depth
- Limited data
Tropic Reservoir in Garfield County, Utah has a water quality grade of A (Excellent). Water clarity: 12.3 ft visibility. Phosphorus: 4.9 µg/L. Chlorophyll-a (algae): 1.3 µg/L.
- Clarity
- 12.3 ft
- Max depth
- ~13 ft est.
- Type
- Oligotrophic
- Phosphorus
- 4.9 µg/L
- Chlorophyll-a
- 1.3 µg/L
- Trend
- ↑ Improving
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Tropic Reservoir is a cold, clear oligotrophic lake in Garfield County, Utah with an estimated average depth of about 13 feet. Water quality is graded A based on 2 sampling years through 2020. Overall water quality is improving over recent sampling years. Compared to the 9 other monitored lakes in Garfield County, Tropic Reservoir ranks #4 for water quality.
Source: EPA Water Quality Portal sampling records, Utah DWQ, last sampled 2020-08-11. Grade methodology: LakeQuality methodology.
What Tropic Reservoir is good for
From access and monitoring records, not editorial picks.
- Clear water12.3 ft of visibility
- Camping2 public campgrounds nearby
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 A is nutrients and algae, not a swimming clearance. Tropic Reservoir is listed impaired under Clean Water Act §303(d) (IR 5) for pH / acidity. Check local advisories before you swim.
Water Quality Grade: A (Excellent)
Good clarity, visible to about 12.3 ft. Phosphorus 4.9 µg/L. Chlorophyll-a 1.3 µg/L. TSI 34. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 12.3 ft | Not graded |
| Phosphorus | 4.9 µg/L | Good |
| Chlorophyll-a (Algae) | 1.3 µg/L | Good |
| Trophic State Index (TSI) | 34 | Oligotrophic |
Low nutrients, clear water. The letter is not a swimming clearance.
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~13 ft est. |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Utah has not published bathymetry for Tropic 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
Public campgrounds near Tropic Reservoir
- King Creek Campground0.3 km
- King Creek Group Area0.9 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
Fishing Tropic Reservoir
Water Quality Trend: ↑ Improving
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.256 m/yr | 2 |
| Chlorophyll-a | → Stable | +0.01 µg/L/yr | 2 |
Reservoir Info (USACE NID)
Tropic Reservoir is a man-made reservoir impounded by the Tropic (completed 1936), built primarily for irrigation on the East Fork of Sevier River; earth-type dam, 29 ft tall and 752 ft long.
- Normal storage
- 1,850 ac-ft
- Max storage
- 3,700 ac-ft
- Drainage area
- 86.1 sq mi
- Hazard class
- High
- Owner
- TROPIC-EAST FORK IRRIGATION COMPANY
Source: USACE National Inventory of Dams, NID ID UT00302 · Operator website
EPA Impairment Status
Tropic Reservoir is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit UT-L-16030002-002_00 · Official waterbody report
County Ranking
Ranked #4 of 10 lakes in Garfield County
Nearby Lakes in Garfield County
Frequently asked questions about Tropic Reservoir
Where is Tropic Reservoir?
- Tropic Reservoir is a lake in Garfield County, Utah. LakeQuality grades it A for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Tropic Reservoir?
- Tropic Reservoir in Garfield County, Utah has a water quality grade of A (Excellent). Water clarity: 12.3 ft visibility. Phosphorus: 4.9 µg/L. Chlorophyll-a (algae): 1.3 µg/L.
Is Tropic Reservoir safe to swim in?
- The A is nutrients and algae, not a swimming clearance. Tropic Reservoir is listed impaired under Clean Water Act §303(d) (IR 5) for pH / acidity. Check local advisories before you swim.
How deep is Tropic Reservoir?
- No published bathymetric survey covers Tropic Reservoir, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 13 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 campgrounds on Tropic Reservoir?
- Tropic Reservoir has 2 public campgrounds from USGS The National Map within 5 km, including King Creek Campground, King Creek Group Area. 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 Tropic Reservoir across LakeQuality
Species activity outlook by water temperature and season
Where to stay at Utah's top lakes, each with its grade
Low nutrients, clear water. The letter is not a swimming clearance.
Utah's cleanest and most-polluted lakes, ranked
Planning a trip around Bryce Canyon?
Tropic Reservoir is about 4 miles from Bryce Canyon National Park. 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 Bryce Canyon →More Utah Lake Rankings
Other Grade A Lakes in Utah
Oligotrophic Lakes in Utah
Where this data comes from
11 measurements from 1 monitoring station, 2020. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Utah Department Of Environmental Quality
UTAHDWQ_WQX11 samples · 2020
Analytical methods
- Field Measurements
- Phosphorus by Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
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.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)
Public campgrounds from USGS The National Map Structures, within about 3 miles