Hyrum Reservoir
Cache County, Utah480 acresView mapDirections
Utah DWQ publishes the water-quality measurements for Hyrum Reservoir. Here is what has been measured.
- Mesotrophic
- Impaired · Nutrients (phosphorus, nitrogen)
- Public access
Hyrum Reservoir in Cache County, Utah has water-quality measurements published by Utah DWQ, shown here as reported. Water clarity: 6.9 ft visibility. Phosphorus: 17.9 µg/L. Chlorophyll-a (algae): 2.2 µg/L. Surface area: 480 acres.
Hyrum Reservoir is a 480-acre mesotrophic lake in Cache County, Utah. Overall water quality is improving over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 8 other monitored lakes in Cache County, Hyrum Reservoir ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, Utah DWQ, last sampled 2021-09-15. Methodology: how these readings are compared.
Hyrum Reservoir covers about 480 acres in Cache County. It has one public boat landing. If you are planning to stay, you can search lake houses and cabins around Hyrum Reservoir on Vrbo, or look for a hotel room near the lake on Booking.com or Expedia.
What Hyrum Reservoir is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
Swimming conditions
Readings onlyLow 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. Hyrum Reservoir is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether Hyrum 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 Hyrum Reservoir
These are the measurements Utah DWQ publishes for Hyrum 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 6.9 ft. Phosphorus 17.9 µg/L. Chlorophyll-a 2.2 µg/L. TSI 44.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 6.9ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 17.9µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 2.2µg/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. | 44 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Hyrum Reservoir
Answers come straight from the public measurements and survey records on this page.
Lake Details
Surface area
480 acres
Public access
Yes
Listed by Utah DWQ
No bathymetric survey has been published for Hyrum Reservoir, so its depth is not documented here.
Recreation & Access
- Hyrum State ParkPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Hyrum Reservoir
Compare lakeside cabins, hotels, and vacation rentals near Hyrum Reservoir in Cache 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.
Top-rated places to stay near Hyrum Reservoir
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Fishing Hyrum Reservoir
Water Quality Trend: Improving
Based on 5 years of monitoring (2015–2021).
Water clarity
Improving5 years
Phosphorus
Worsening+1.4 µg/L/yr2 years
Chlorophyll-a
Improving-0.1 µg/L/yr3 years
Reservoir Info (USACE NID)
Hyrum Reservoir is a man-made reservoir impounded by the Hyrum Dike (completed 1935), built primarily for irrigation on the Little Bear River; earth-type dam, 18 ft tall and 850 ft long.
- Surface area
- 480 ac
- Normal storage
- 18,685 ac-ft
- Max storage
- 18,685 ac-ft
- Hazard class
- High
- Owner
- BUREAU OF RECLAMATION
All listed purposes: Irrigation;Recreation;Water Supply.
Source: USACE National Inventory of Dams, NID ID UT10123 · Operator website
EPA Impairment Status
Hyrum 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-16010203-005_00 · Official waterbody report
Nearby Lakes in Cache County
Frequently asked questions about Hyrum Reservoir
Where is Hyrum Reservoir?
- Hyrum 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 Hyrum Reservoir?
- Hyrum Reservoir in Cache County, Utah has water-quality measurements published by Utah DWQ, shown here as reported. Water clarity: 6.9 ft visibility. Phosphorus: 17.9 µg/L. Chlorophyll-a (algae): 2.2 µg/L. Surface area: 480 acres.
Is Hyrum Reservoir safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Hyrum Reservoir is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Are there boat ramps on Hyrum Reservoir?
- Hyrum Reservoir has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Hyrum State Park. Public access is listed as yes.
Can I fish at Hyrum Reservoir?
- Hyrum 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.
Explore Hyrum Reservoir across LakeQuality
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Other Lakes in Utah
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Where this data comes from
194 measurements from 2 monitoring stations, 2015–2021. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Utah Department Of Environmental Quality
UTAHDWQ_WQX194 samples · 2015–2021
Analytical methods
- Field Measurements
- Phosphorus by Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
Monitoring station identifiers (2)
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
Named boat-access points from the USGS National Boat Ramps inventory