Patagonia Lake
Santa Cruz County, Arizona260 acresView mapDirections
Not enough samples to grade — no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years). No letter yet. Here is what we do have.
- Impaired · Mercury
- 16 ft max depth
- Public access
- Limited data
Patagonia Lake in Santa Cruz County, Arizona is not rated for water quality — its monitoring record does not meet the evidence bar. Surface area: 260 acres.
- Max depth
- ~16 ft est.
- Area
- 260 acres
- Trend
- → Stable
- Public access
- Yes
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Stays near Patagonia Lake
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Watch Patagonia Lake’s letter
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Why Patagonia Lake has no grade
We grade a lake only when the monitoring record supports a letter: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For Patagonia Lake, no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years).
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. Everything below that has been measured is still reported on this page.
Sampling is run by ADEQ and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Patagonia Lake is a 260-acre lake in Santa Cruz County, Arizona with an estimated average depth of about 16 feet. Water clarity is improving 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, ADEQ, last sampled 2026-04-06. Grade methodology: LakeQuality methodology.
What Patagonia Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
Swimming Safety
Not ratedLimited data
The letter is not a swimming clearance. Patagonia Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury. Check local advisories before you swim.
Water quality measurements for Patagonia Lake
These readings exist but are not enough for an A–F grade — see why.
No clarity data.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples |
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~16 ft est. |
| Surface Area | 260 acres |
| Public Access | Yes |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Arizona has not published bathymetry for Patagonia 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.
Recreation & Access
- Patagonia LakePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Patagonia Lake
Water Quality Trend: → Stable
Based on 3 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.256 m/yr | 3 |
| Phosphorus | ↓ Declining | +12.25 µg/L/yr | 2 |
Reservoir Info (USACE NID)
Patagonia Lake is a man-made reservoir impounded by the Lake Patagonia (completed 1968), built primarily for recreation on the Sonoita Creek; earth-type dam, 157 ft tall and 970 ft long.
- Surface area
- 260 ac
- Normal storage
- 7,540 ac-ft
- Drainage area
- 235 sq mi
- Hazard class
- High
- Owner
- ARIZONA STATE PARKS
Source: USACE National Inventory of Dams, NID ID AZ00029 · Operator website
EPA Impairment Status
Patagonia Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit AZL15050301-1050_00 · Official waterbody report
Graded lakes near Patagonia Lake
Patagonia Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Santa Cruz County
Frequently asked questions about Patagonia Lake
Where is Patagonia Lake?
- Patagonia Lake is a lake in Santa Cruz County, Arizona. LakeQuality has not rated this lake (UNRATED) — no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years).
What is the water quality grade for Patagonia Lake?
- Patagonia Lake in Santa Cruz County, Arizona is not rated for water quality — its monitoring record does not meet the evidence bar. Surface area: 260 acres.
Is Patagonia Lake safe to swim in?
- The letter is not a swimming clearance. Patagonia Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury. Check local advisories before you swim.
How deep is Patagonia Lake?
- No published bathymetric survey covers Patagonia Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 16 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 260 acres.
Are there boat ramps on Patagonia Lake?
- Patagonia Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Patagonia Lake. Public access is listed as yes.
Explore Patagonia Lake across LakeQuality
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Where this data comes from
5 measurements from 1 monitoring station, 2026. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Great Lakes Environmental Center
GLEC5 samples · 2026
Analytical methods
- 4500 P E ~ Phosphorus in Water by Colorimetry- Ascorbic Acid Method
- 300.0 ~ EPA; Determination of Inorganic Anions by Ion Chromatography
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
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)
Named boat-access points from the USGS National Boat Ramps inventory