Millsite Reservoir
Emery County, UtahView mapDirections
Clarity, phosphorus, and algae all sit in the cleanest band for this region.
- Oligotrophic
- #1 of 10 in the county
- Public access
- Limited data
Millsite Reservoir in Emery County, Utah has a water quality grade of A (Excellent). Water clarity: 10.5 ft visibility. Phosphorus: 20.6 µg/L. Chlorophyll-a (algae): 1.9 µg/L.
- Clarity
- 10.5 ft
- Type
- Oligotrophic
- Phosphorus
- 20.6 µg/L
- Chlorophyll-a
- 1.9 µg/L
- Trend
- ↓ Declining
- Public access
- Yes
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Watch Millsite Reservoir’s letter
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Millsite Reservoir is a cold, clear oligotrophic lake in Emery County, Utah. Water quality is graded A based on 1 sampling years through 2025. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 9 other monitored lakes in Emery County, Millsite Reservoir ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Utah DWQ, last sampled 2025-10-01. Grade methodology: LakeQuality methodology.
What Millsite Reservoir is good for
From access and monitoring records, not editorial picks.
- Clear water10.5 ft of visibility
- Boat launch1 documented ramp
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. Check local advisories before you swim.
Water Quality Grade: A (Excellent)
Good clarity, visible to about 10.5 ft. Phosphorus 20.6 µg/L. Chlorophyll-a 1.9 µg/L. TSI 43. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 10.5 ft | Not graded |
| Phosphorus | 20.6 µg/L | Not graded |
| Chlorophyll-a (Algae) | 1.9 µg/L | Good |
| Trophic State Index (TSI) | 43 | Oligotrophic |
Low nutrients, clear water. The letter is not a swimming clearance.
Recreation & Access
- Millsite State ParkPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Millsite Reservoir
Water Quality Trend: ↓ Declining
Based on 4 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.047 m/yr | 4 |
| Chlorophyll-a | ↓ Declining | +0.05 µg/L/yr | 3 |
Reservoir Info (USACE NID)
Millsite Reservoir is a man-made reservoir impounded by the Millsite (completed 1971), built primarily for irrigation on the Ferron Creek; earth-type dam, 115 ft tall and 4,150 ft long.
- Normal storage
- 18,000 ac-ft
- Max storage
- 20,000 ac-ft
- Drainage area
- 157 sq mi
- Hazard class
- High
- Owner
- FERRON CANAL AND RESERVOIR COMPANY
Source: USACE National Inventory of Dams, NID ID UT00212 · Operator website
County Ranking
Ranked #1 of 10 lakes in Emery County
Nearby Lakes in Emery County
Frequently asked questions about Millsite Reservoir
Where is Millsite Reservoir?
- Millsite Reservoir is a lake in Emery County, Utah. LakeQuality grades it A for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Millsite Reservoir?
- Millsite Reservoir in Emery County, Utah has a water quality grade of A (Excellent). Water clarity: 10.5 ft visibility. Phosphorus: 20.6 µg/L. Chlorophyll-a (algae): 1.9 µg/L.
Is Millsite Reservoir safe to swim in?
- The A is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Are there boat ramps on Millsite Reservoir?
- Millsite Reservoir has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Millsite State Park. Public access is listed as yes.
Explore Millsite 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.
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Other Grade A Lakes in Utah
Oligotrophic Lakes in Utah
Where this data comes from
59 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_WQX59 samples · 2013–2025
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
Named boat-access points from the USGS National Boat Ramps inventory