Alameda County Lake Quality
California, 7 lakes — no lake here has enough monitoring data for a grade
Only 7 lakes in Alameda County carry an active grade. The county-level summary is therefore representative of those specific lakes, not necessarily of every water body in the county.
Most of the county's monitored lakes are shallow — under 50 feet — which means wind keeps the water column mixed all summer and sediment-bound phosphorus releases back into the surface layer whenever the bottom is disturbed. Don Castro Reservoir (—) is the cleanest in the county.
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Quick Answers for Alameda County
Planning a trip? Check special fishing regulations for Don Castro Reservoir — or check the official California fishing regulations.
All Lakes in Alameda County
7 lakes · 0 graded, 7 not rated0 graded lakes · 7 not rated, hidden
| # | Lake | Grade | Clarity | Phosphorus | Algae | Trophic | Access |
|---|---|---|---|---|---|---|---|
| NRDon Castro ReservoirAlameda | NR | 0.3 ft | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRHorseshoe LakeAlameda | NR | 12.7 ft | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRJordan PondAlameda | NR | 2.5 ft | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRLake ChabotAlameda | NR | 5.3 ft | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRLake Del ValleAlameda | NR | 7 ft | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRLake MerrittAlameda | NR | 5.2 ft | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRLake TemescalAlameda | NR | 6.2 ft | No recent samples | No recent samples | No recent samples | Not recorded |
NR = not rated: the monitoring record does not meet the evidence bar for a grade. That is EPA Integrated Reporting Category 3 (insufficient information), not a failing grade. How grading works.
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Other Counties in California
See how Alameda County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all 49 states and 2 Canadian provinces.
Source: EPA National Aquatic Resource Surveys, 2026.