Standley Lake
Jefferson County, Colorado1,222 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.
- 95 ft max depth
- Limited data
Standley Lake in Jefferson County, Colorado is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 20.5 ft visibility. Surface area: 1222 acres.
- Clarity
- 20.5 ft
- Max depth
- ~95 ft est.
- Area
- 1,222 acres
- Trend
- → Stable
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Watch Standley Lake’s letter
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Why Standley Lake has no grade
Standley 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, Standley Lake is Not Rated — not an F. Its 20.5-foot median from 36 readings collected 2020–2025 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 CDPHE and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Standley Lake is a 1,222-acre lake in Jefferson County, Colorado with an estimated average depth of about 95 feet.
Source: EPA Water Quality Portal sampling records, CDPHE, last sampled 2025-07-28. Grade methodology: LakeQuality methodology.
What Standley Lake is good for
From access and monitoring records, not editorial picks.
- Clear water20.5 ft of visibility
- Big water1,222 acres
Swimming Safety
Not ratedLimited data
The letter is not a swimming clearance. Check local advisories before you swim.
Water quality measurements for Standley Lake
These readings exist but are not enough for an A–F grade — see why.
Crystal clear, you can see 20.5 ft down. TSI 34.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 20.5 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 34 | Oligotrophic |
Low nutrients, clear water. The letter is not a swimming clearance.
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~95 ft est. |
| Average Depth | ~45 ft est. |
| Surface Area | 1,222 acres |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Colorado has not published bathymetry for Standley Lake.
Lake Size & Watershed
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.
Fishing Standley Lake
Water Quality Trend: → Stable
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | +0.12 m/yr | 6 |
Reservoir Info (USACE NID)
Standley Lake is a man-made reservoir impounded by the Standley Lake (completed 1913), built primarily for irrigation on the Big Dry Creek; earth-type dam, 123 ft tall and 5,900 ft long.
- Surface area
- 1,222 ac
- Normal storage
- 43,344 ac-ft
- Max storage
- 54,740 ac-ft
- Drainage area
- 15 sq mi
- Hazard class
- High
- Owner
- FARMERS RESERVOIR AND IRRIGATION COMPANY (EDGAR, S
All listed purposes: Irrigation;Water Supply.
Source: USACE National Inventory of Dams, NID ID CO00101 · Operator website
Graded lakes near Standley Lake
Standley Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Jefferson County
Frequently asked questions about Standley Lake
Where is Standley Lake?
- Standley Lake is a lake in Jefferson County, Colorado. 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 Standley Lake?
- Standley Lake in Jefferson County, Colorado is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 20.5 ft visibility. Surface area: 1222 acres.
Is Standley Lake safe to swim in?
- The letter is not a swimming clearance. Check local advisories before you swim.
How deep is Standley Lake?
- No published bathymetric survey covers Standley Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 95 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate. The lake covers 1222 acres.
Explore Standley Lake across LakeQuality
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Where this data comes from
36 measurements from 1 monitoring station, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- North American Lake Management Society
NALMS36 samples · 2020–2025
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
Lake size & watershed from HydroLAKES (HydroSHEDS)