Willard Bay Reservoir
Box Elder County, Utah9,950 acresView mapDirections
Utah DWQ publishes the water-quality measurements for Willard Bay Reservoir. Here is what has been measured.
- Eutrophic
Willard Bay Reservoir in Box Elder County, Utah has water-quality measurements published by Utah DWQ, shown here as reported. Water clarity: 2.3 ft visibility. Phosphorus: 55 µg/L. Chlorophyll-a (algae): 7.9 µg/L. Surface area: 9950 acres.
Willard Bay Reservoir is a 9,950-acre productive, nutrient-rich eutrophic lake in Box Elder County, Utah. Overall water quality is declining over recent sampling years. Compared to the 14 other monitored lakes in Box Elder County, Willard Bay Reservoir ranks #7 for water quality.
Source: EPA Water Quality Portal sampling records, Utah DWQ, last sampled 2023-10-10. Methodology: how these readings are compared.
At about 10,000 acres, Willard Bay Reservoir is large enough that where you stay decides which shore you see most of. Vrbo is where to look for cabins and lake homes around Willard Bay Reservoir, and Booking.com and Expedia search hotels near the lake for your dates.
What Willard Bay Reservoir is good for
From access and monitoring records, not editorial picks.
- Big water9,950 acres
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 Willard Bay 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 Willard Bay Reservoir
These are the measurements Utah DWQ publishes for Willard Bay Reservoir, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Very murky, less than 2.3 ft of visibility. Phosphorus 55 µg/L. Chlorophyll-a 7.9 µg/L. TSI 59.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 2.3ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 55µg/L | Fair GoodFairPoor |
| Chlorophyll-a (algae) | 7.9µg/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. | 59 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Willard Bay Reservoir
Answers come straight from the public measurements and survey records on this page.
Lake Details
Surface area
9,950 acres
No bathymetric survey has been published for Willard Bay Reservoir, so its depth is not documented here.
Stays via Stay22
Stays near Willard Bay Reservoir
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Top-rated places to stay near Willard Bay Reservoir
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Fishing Willard Bay Reservoir
Water Quality Trend: Worsening
Based on 6 years of monitoring (2015–2023).
Water clarity
Worsening6 years
Phosphorus
Worsening+1.36 µg/L/yr4 years
Chlorophyll-a
Improving-2.07 µg/L/yr4 years
Reservoir Info (USACE NID)
Willard Bay Reservoir is a man-made reservoir impounded by the Arthur V. Watkins Dam (completed 1964), built primarily for irrigation on the Bear River Offstream; earth-type dam, 38 ft tall and 76,665 ft long.
- Surface area
- 9,950 ac
- Normal storage
- 215,500 ac-ft
- Max storage
- 223,000 ac-ft
- Drainage area
- 16 sq mi
- Hazard class
- High
- Owner
- BUREAU OF RECLAMATION
Source: USACE National Inventory of Dams, NID ID UT10112 · Operator website
Nearby Lakes in Box Elder County
Frequently asked questions about Willard Bay Reservoir
Where is Willard Bay Reservoir?
- Willard Bay Reservoir is a lake in Box Elder County, Utah. Its water-quality measurements are published by Utah DWQ and shown on this page as reported.
What is the water quality of Willard Bay Reservoir?
- Willard Bay Reservoir in Box Elder County, Utah has water-quality measurements published by Utah DWQ, shown here as reported. Water clarity: 2.3 ft visibility. Phosphorus: 55 µg/L. Chlorophyll-a (algae): 7.9 µg/L. Surface area: 9950 acres.
Is Willard Bay Reservoir safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
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Where this data comes from
72 measurements from 1 monitoring station, 2015–2023. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Utah Department Of Environmental Quality
UTAHDWQ_WQX72 samples · 2015–2023
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.