Porcupine Reservoir
Cache County, UtahView mapDirections
Utah DWQ publishes the water-quality measurements for Porcupine Reservoir. Here is what has been measured.
- Mesotrophic
Porcupine Reservoir in Cache County, Utah has water-quality measurements published by Utah DWQ, shown here as reported. Water clarity: 8.5 ft visibility. Phosphorus: 13.3 µg/L. Chlorophyll-a (algae): 3.8 µg/L.
Porcupine Reservoir is a mesotrophic lake in Cache County, Utah. Overall water quality is improving over recent sampling years. Compared to the 8 other monitored lakes in Cache County, Porcupine Reservoir ranks #6 for water quality.
Source: EPA Water Quality Portal sampling records, Utah DWQ, last sampled 2021-09-13. Methodology: how these readings are compared.
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Swimming conditions
Readings onlyModerate algae
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. Check local advisories before you swim.
Whether Porcupine 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 Porcupine Reservoir
These are the measurements Utah DWQ publishes for Porcupine 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 8.5 ft. Phosphorus 13.3 µg/L. Chlorophyll-a 3.8 µg/L. TSI 44.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 8.5ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 13.3µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 3.8µg/L | Fair GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 44 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Porcupine Reservoir
Answers come straight from the public measurements and survey records on this page.
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Stays near Porcupine Reservoir
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Fishing Porcupine Reservoir
Water Quality Trend: Improving
Based on 4 years of monitoring (2015–2021).
Water clarity
Worsening4 years
Phosphorus
Improving-4.5 µg/L/yr2 years
Chlorophyll-a
Improving-1.35 µg/L/yr3 years
Reservoir Info (USACE NID)
Porcupine Reservoir is a man-made reservoir impounded by the Porcupine (completed 1962), built primarily for irrigation on the East Fk Little Bear River; earth-type dam, 181 ft tall and 665 ft long.
- Normal storage
- 13,000 ac-ft
- Max storage
- 15,000 ac-ft
- Drainage area
- 72 sq mi
- Hazard class
- High
- Owner
- PORCUPINE RESERVOIR COMPANY
Source: USACE National Inventory of Dams, NID ID UT00251 · Operator website
Nearby Lakes in Cache County
Frequently asked questions about Porcupine Reservoir
Where is Porcupine Reservoir?
- Porcupine Reservoir is a lake in Cache County, Utah. Its water-quality measurements are published by Utah DWQ and shown on this page as reported.
What is the water quality of Porcupine Reservoir?
- Porcupine Reservoir in Cache County, Utah has water-quality measurements published by Utah DWQ, shown here as reported. Water clarity: 8.5 ft visibility. Phosphorus: 13.3 µg/L. Chlorophyll-a (algae): 3.8 µg/L.
Is Porcupine Reservoir safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Explore Porcupine Reservoir across LakeQuality
More lakes in Utah
Other Lakes in Utah
Mesotrophic Lakes in Utah
Where this data comes from
142 measurements from 1 monitoring station, 2015–2021. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Utah Department Of Environmental Quality
UTAHDWQ_WQX142 samples · 2015–2021
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.