San Joaquin County Lake Quality
California, 6 lakes, average grade A (Excellent)
San Joaquin County has 6 graded lakes — a thin enough sample that one or two stressed lakes can move the county average noticeably. Use the per-lake pages below for what actually matters. The county's average grade is A — among the cleanest in California. 1 lakes pull an A on their own, and almost none fall into the D or F brackets.
The county's lakes lean shallow, which makes the grades sensitive to wind, sediment-resuspension, and any nutrient inputs from the watershed. The cleanest lake on the books is Staten Island Lake (A); the most-stressed is Staten Island Lake (A).
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Quick Answers for San Joaquin County
Planning a trip? Check special fishing regulations for Staten Island Lake — or check the official California fishing regulations.
All Lakes in San Joaquin County
6 lakes · 1 graded, 5 not rated1 graded lake · 5 not rated, hidden
| # | Lake | Grade | Clarity | Phosphorus | Algae | Trophic | Access |
|---|---|---|---|---|---|---|---|
| 1 | AStaten Island LakeSan Joaquin | A | No recent samples | No recent samples | 5.7 µg/L | No recent samples | Not recorded |
| NRBacon Island North PondSan Joaquin | NR | No recent samples | No recent samples | 258.2 µg/L | No recent samples | Not recorded | |
| NRBacon Island South PondSan Joaquin | NR | No recent samples | No recent samples | 26.4 µg/L | No recent samples | Not recorded | |
| NRBouldin Island East PondSan Joaquin | NR | No recent samples | No recent samples | 19 µg/L | No recent samples | Not recorded | |
| NRBouldin Island West PondSan Joaquin | NR | No recent samples | No recent samples | 23.2 µg/L | No recent samples | Not recorded | |
| NRMcleod Lake A Weber Point A StocktonSan Joaquin | NR | No recent samples | 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.
Lake Match
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Six questions — swimming, fishing, quiet, cabins, drive time — and a shortlist of graded lakes that fit, with the water quality behind each one.
Other Counties in California
See how San Joaquin 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.