Alamo Lake
La Paz County, Arizona41,500 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 · Ammonia
- 66 ft max depth
- Public access
- Limited data
Alamo Lake in La Paz County, Arizona is not rated for water quality — its monitoring record does not meet the evidence bar. Surface area: 41500 acres.
- Max depth
- ~66 ft est.
- Area
- 41,500 acres
- Trend
- ↓ Declining
- Public access
- Yes
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Stays near Alamo Lake
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Watch Alamo Lake’s letter
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Why Alamo 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 Alamo 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.
Alamo Lake is a 41,500-acre lake in La Paz County, Arizona with an estimated average depth of about 66 feet. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available.
Source: EPA Water Quality Portal sampling records, ADEQ, last sampled 2026-03-25. Grade methodology: LakeQuality methodology.
What Alamo Lake is good for
From access and monitoring records, not editorial picks.
- Big water41,500 acres
Swimming Safety
Not ratedLimited data
The letter is not a swimming clearance. Alamo Lake is listed impaired under Clean Water Act §303(d) (IR 5) for ammonia, mercury, pH / acidity. Check local advisories before you swim.
Water quality measurements for Alamo 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 | ~66 ft est. |
| Average Depth | ~15 ft est. |
| Surface Area | 41,500 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 Alamo 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 Alamo Lake
Water Quality Trend: ↓ Declining
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.4 m/yr | 2 |
Reservoir Info (USACE NID)
Alamo Lake is a man-made reservoir impounded by the Alamo Dam (completed 1968), built primarily for flood risk reduction on the Bill Williams River; earth-type dam, 283 ft tall and 975 ft long.
- Surface area
- 41,500 ac
- Normal storage
- 0 ac-ft
- Max storage
- 1,409,000 ac-ft
- Drainage area
- 4,770 sq mi
- Hazard class
- High
- Owner
- USACE - Los Angeles District
All listed purposes: Flood Risk Reduction;Fish and Wildlife Pond;Recreation.
Source: USACE National Inventory of Dams, NID ID AZ82203 · Operator website
EPA Impairment Status
Alamo 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 AZL15030204-0040A_00 · Official waterbody report
Graded lakes near Alamo Lake
Alamo Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in La Paz County
Frequently asked questions about Alamo Lake
Where is Alamo Lake?
- Alamo Lake is a lake in La Paz 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 Alamo Lake?
- Alamo Lake in La Paz County, Arizona is not rated for water quality — its monitoring record does not meet the evidence bar. Surface area: 41500 acres.
Is Alamo Lake safe to swim in?
- The letter is not a swimming clearance. Alamo Lake is listed impaired under Clean Water Act §303(d) (IR 5) for ammonia, mercury, pH / acidity. Check local advisories before you swim.
How deep is Alamo Lake?
- No published bathymetric survey covers Alamo Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 66 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 41500 acres.
Explore Alamo Lake across LakeQuality
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Where this data comes from
7 measurements from 2 monitoring stations, 2025–2026. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Great Lakes Environmental Center
GLEC5 samples · 2026 - AZDEQ_SW
AZDEQ_SW2 samples · 2025
Analytical methods
- 4500 P E ~ Phosphorus in Water by Colorimetry- Ascorbic Acid Method
- 300.0 ~ EPA; Determination of Inorganic Anions by Ion Chromatography
- EPA 365.1
- FIELD
Monitoring station identifiers (2)
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)