Willard South Marina Lake
Box Elder County, Utah9,950 acresView mapDirections
Not Rated: one monitoring station are on record, but they measured water clarity only. LakeQuality’s A–F method grades total phosphorus, total nitrogen, chlorophyll-a, and turbidity; clarity is shown, not scored.
- Public access
- Limited data
Willard South Marina Lake in Box Elder County, Utah is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 2.2 ft visibility. Surface area: 9950 acres.
- Clarity
- 2.2 ft
- Area
- 9,950 acres
- Trend
- → Stable
- Public access
- Yes
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Watch Willard South Marina Lake’s letter
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Why Willard South Marina Lake has no grade
Willard South Marina Lake has monitoring on record from one station, but only water clarity was measured. LakeQuality’s A–F letter uses total phosphorus, total nitrogen, chlorophyll-a, and turbidity against EPA National Lakes Assessment condition classes. With none of those grading measurements on record, Willard South Marina Lake is Not Rated — not an F. Its 2.2-foot median from 24 readings collected 2012–2016 is still shown as clarity, but clarity alone cannot earn a letter.
Not Rated is EPA Integrated Reporting Category 3 — insufficient information. Everything below that has been measured is still reported on this page.
Sampling is run by Utah DWQ and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Willard South Marina Lake is a 9,950-acre lake in Box Elder County, Utah. Phosphorus level is declining over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing.
Source: EPA Water Quality Portal sampling records, Utah DWQ, last sampled 2016-07-14. Grade methodology: LakeQuality methodology.
What Willard South Marina Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
- Big water9,950 acres
Swimming Safety
Not ratedLimited data
The letter is not a swimming clearance. Check local advisories before you swim.
Water quality measurements for Willard South Marina Lake
These readings exist but are not enough for an A–F grade — see why.
Very murky, less than 2.2 ft of visibility. TSI 66.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.2 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 66 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 9,950 acres |
| Public Access | Yes |
No bathymetric survey has been published for Willard South Marina Lake, so its depth is not documented here.
Recreation & Access
- Willard Bay South MarinaPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Willard South Marina Lake
Water Quality Trend: → Stable
Based on 9 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | -0.01 m/yr | 9 |
| Phosphorus | ↓ Declining | +5.55 µg/L/yr | 3 |
| Chlorophyll-a | ↑ Improving | -6.5 µg/L/yr | 3 |
Reservoir Info (USACE NID)
Willard South Marina Lake 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 · Matched by proximity (0.12 km)
Graded lakes near Willard South Marina Lake
Willard South Marina Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Box Elder County
Frequently asked questions about Willard South Marina Lake
Where is Willard South Marina Lake?
- Willard South Marina Lake is a lake in Box Elder County, Utah. LakeQuality has not rated this lake (UNRATED) — the only measurement available is water clarity, which is not a water-quality indicator on its own — EPA's National Lakes Assessment does not grade clarity.
What is the water quality grade for Willard South Marina Lake?
- Willard South Marina Lake in Box Elder County, Utah is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 2.2 ft visibility. Surface area: 9950 acres.
Is Willard South Marina Lake safe to swim in?
- The letter is not a swimming clearance. Check local advisories before you swim.
Are there boat ramps on Willard South Marina Lake?
- Willard South Marina Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Willard Bay South Marina. Public access is listed as yes.
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Where this data comes from
24 measurements from 1 monitoring station, 2012–2016. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- UC Region of USBOR
UC_REGION_USBOR_WQX24 samples · 2012–2016
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