Nine Mile Reservoir
Sanpete County, UtahView mapDirections
Utah DWQ publishes the water-quality measurements for Nine Mile Reservoir. Here is what has been measured.
- Mesotrophic
- Impaired · Nutrients (phosphorus, nitrogen)
- 23 ft max depth
- Limited data
Nine Mile Reservoir in Sanpete County, Utah has water-quality measurements published by Utah DWQ, shown here as reported. Water clarity: 9.3 ft visibility. Phosphorus: 13 µg/L. Chlorophyll-a (algae): 2.5 µg/L.
Nine Mile Reservoir is a mesotrophic lake in Sanpete County, Utah with an estimated average depth of about 23 feet. Compared to the 10 other monitored lakes in Sanpete County, Nine Mile Reservoir ranks #5 for water quality.
Source: EPA Water Quality Portal sampling records, Utah DWQ, last sampled 2020-08-03. Methodology: how these readings are compared.
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. Nine Mile Reservoir is listed impaired under Clean Water Act §303(d) (IR 5) for nutrients (phosphorus, nitrogen), oxygen depletion (low DO), pH / acidity, temperature. Check local advisories before you swim.
Whether Nine Mile 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 Nine Mile Reservoir
These are the measurements Utah DWQ publishes for Nine Mile Reservoir, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Moderate clarity, visible to about 9.3 ft. Phosphorus 13 µg/L. Chlorophyll-a 2.5 µg/L. TSI 42.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 9.3ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 13µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 2.5µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 42 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Nine Mile Reservoir
Answers come straight from the public measurements and survey records on this page.
Lake Details
Max depth
~23 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 Nine Mile Reservoir.
Lake Size & Watershed
Watershed (drainage) area
3 sq mi
HydroLAKES / HydroSHEDS
Surface area
175 acres
HydroLAKES / HydroSHEDS
Shoreline
2.2 mi
HydroLAKES / HydroSHEDS
Elevation
5,397 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.
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Fishing Nine Mile Reservoir
Reservoir Info (USACE NID)
Nine Mile Reservoir is a man-made reservoir impounded by the Ninemile (completed 1900), built primarily for irrigation on the Nine Mile Creek; earth-type dam, 55 ft tall and 825 ft long.
- Normal storage
- 3,500 ac-ft
- Max storage
- 4,300 ac-ft
- Drainage area
- 4 sq mi
- Hazard class
- High
- Owner
- GUNNISON IRRIGATION COMPANY
Source: USACE National Inventory of Dams, NID ID UT00138 · Operator website
EPA Impairment Status
Nine Mile Reservoir is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Designated uses not supporting: Aquatic life.
Source: EPA ATTAINS assessment unit UT-L-16030004-001_00 · Official waterbody report
Nearby Lakes in Sanpete County
Frequently asked questions about Nine Mile Reservoir
Where is Nine Mile Reservoir?
- Nine Mile Reservoir is a lake in Sanpete County, Utah. Its water-quality measurements are published by Utah DWQ and shown on this page as reported.
What is the water quality of Nine Mile Reservoir?
- Nine Mile Reservoir in Sanpete County, Utah has water-quality measurements published by Utah DWQ, shown here as reported. Water clarity: 9.3 ft visibility. Phosphorus: 13 µg/L. Chlorophyll-a (algae): 2.5 µg/L.
Is Nine Mile Reservoir safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Nine Mile Reservoir is listed impaired under Clean Water Act §303(d) (IR 5) for nutrients (phosphorus, nitrogen), oxygen depletion (low DO), pH / acidity, temperature. Check local advisories before you swim.
How deep is Nine Mile Reservoir?
- No published bathymetric survey covers Nine Mile Reservoir, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 23 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
Explore Nine Mile Reservoir across LakeQuality
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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)
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)