Lake Anza
Lake Anza in Contra Costa County, California is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 12.3 ft visibility. Surface area: 10 acres.
- Clarity
- 12.3 ft
- Area
- 10 acres
Why Lake Anza has no grade
We grade a lake only when its monitoring record clears the evidence bar: 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 Lake Anza, no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years). Sampling here has recorded water clarity, but not phosphorus and algae (chlorophyll-a).
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 your state environmental agency and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Lake Anza is a 10-acre lake in Contra Costa County, California.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2023-07-25. Grade methodology: LakeGrade methodology.
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Swimming Safety
Not ratedLimited data
Not rated for swimming — there is not enough monitoring data to judge this lake
Water quality measurements for Lake Anza
These readings exist but do not meet the evidence bar for an A–F grade — see why.
Good clarity, visible to about 12.3 ft. Trophic State Index: 41.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 12.3 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 41 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Lake Anza
Compare lakeside cabins, hotels, and vacation rentals near Lake Anza in Contra Costa County, California — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
Top-rated places to stay near Lake Anza
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Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 10 acres |
No bathymetric survey has been published for Lake Anza, so its depth is not documented here.
Fishing Lake Anza
Reservoir Info (USACE NID)
Lake Anza is a man-made reservoir impounded by the C.L. Tilden Park (completed 1938), built primarily for other on the Wildcat Creek; earth-type dam, 88 ft tall and 355 ft long.
- Surface area
- 10 ac
- Max storage
- 268 ac-ft
- Drainage area
- 1.56 sq mi
- Hazard class
- High
- Owner
- East Bay Regional Park District
All listed purposes: Other;Recreation;Water Supply.
Source: USACE National Inventory of Dams, NID ID CA00161 · Operator website · Matched by proximity (0.19 km)
Graded lakes near Lake Anza
Lake Anza has no grade, but these lakes within a short drive do.
Nearby Lakes in Contra Costa County
Frequently asked questions about Lake Anza
Where is Lake Anza?
- Lake Anza is a lake in Contra Costa County, California. LakeQuality has not rated this lake (UNRATED) — there is not enough recent sampling to assign a letter.
What is the water quality grade for Lake Anza?
- Lake Anza in Contra Costa County, California is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 12.3 ft visibility. Surface area: 10 acres.
Is Lake Anza safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Lake Anza is not rated for water quality — its monitoring record does not meet the evidence bar. Always check local health department advisories before swimming.
Explore Lake Anza across LakeGrade
More California Lake Rankings
Other Lakes in California
Mesotrophic Lakes in California
Where this data comes from
3 measurements from 1 monitoring station, 2021–2023. Retrieved from the EPA Water Quality Portal on 2026-08-21.
Collected and reported by
- North American Lake Management Society
NALMS3 samples · 2021–2023
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.