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LakeQuality

Data Report · Updated July 2026

The State of Arizona’s Lakes 2026

Of 81 monitored lakes in Arizona, 8.6% earn a water-quality grade of A or B and 55.6% score D or F (average grade D). Nla Lake is the cleanest;

81
Monitored lakes graded
D
Average grade
8.6%
Grade A or B
0%
On impaired list

Arizona grade distribution

C
D
F
A: 4 (4.9%)B: 3 (3.7%)C: 29 (35.8%)D: 19 (23.5%)F: 26 (32.1%)

Cleanest lakes in Arizona

Highest combined water-quality score, 2026.

  1. 1.ANla Lake — Yavapai County16.6 ft clarity · 13 µg/L P · 1 µg/L chl-a
  2. 2.ANla Lake — Cochise County8.4 ft clarity · 14 µg/L P · 4 µg/L chl-a
  3. 3.ANla Lake — Coconino County10.0 ft clarity · 14 µg/L P · 4 µg/L chl-a
  4. 4.ANla Lake — Maricopa County10.0 ft clarity · 9 µg/L P · 4 µg/L chl-a
  5. 5.BAk-Chin Reservoir — Pinal County27 µg/L P · 4 µg/L chl-a
  6. 6.CNla Lake — Maricopa County5.6 ft clarity · 49 µg/L P · 17 µg/L chl-a
  7. 7.CNla Lake — Maricopa County5.1 ft clarity · 38000 µg/L P · 2 µg/L chl-a
  8. 8.CNla Lake — Maricopa County4.0 ft clarity · 40 µg/L P · 11 µg/L chl-a
  9. 9.CNla Lake — Yuma County1.5 ft clarity · 39 µg/L P · 8 µg/L chl-a
  10. 10.CNla Lake — Graham County2.8 ft clarity · 38000 µg/L P · 7 µg/L chl-a

Most-polluted lakes

Lowest combined water-quality score among monitored lakes.

  1. 1.FNla Lake — Yuma County0.1 ft clarity · 392000 µg/L P · 232 µg/L chl-a
  2. 2.FNla Lake — Coconino County2.5 ft clarity · 397 µg/L P · 68 µg/L chl-a
  3. 3.FNla Lake — Coconino County0.9 ft clarity · 519 µg/L P · 145 µg/L chl-a
  4. 4.FNla Lake — Apache County0.9 ft clarity · 882000 µg/L P · 224 µg/L chl-a
  5. 5.DNla Lake — Apache County5.1 ft clarity · 468 µg/L P · 32 µg/L chl-a
  6. 6.DNla Lake — Coconino County5.7 ft clarity · 75000 µg/L P · 10 µg/L chl-a
  7. 7.DNla Lake — Apache County0.9 ft clarity · 161 µg/L P · 9 µg/L chl-a
  8. 8.DNla Lake — La Paz County4.9 ft clarity · 37000 µg/L P · 9 µg/L chl-a
  9. 9.DNla Lake — Yavapai County192 µg/L P · 18 µg/L chl-a
  10. 10.CNla Lake — Graham County2.8 ft clarity · 38000 µg/L P · 7 µg/L chl-a

Worst algae hotspots

Highest measured chlorophyll-a (algae) concentration.

  1. 1.FNla Lake — Yuma County232 µg/L chlorophyll-a
  2. 2.FNla Lake — Apache County224 µg/L chlorophyll-a
  3. 3.FNla Lake — Coconino County145 µg/L chlorophyll-a
  4. 4.FNla Lake — Coconino County68 µg/L chlorophyll-a
  5. 5.DNla Lake — Apache County32 µg/L chlorophyll-a

Explore Arizona lakes

Lake Fishing Forecast

Species activity outlook by water temperature and season

Grades combine Secchi clarity, total phosphorus, and chlorophyll-a from the EPA Water Quality Portal and state agencies. See the full methodology, the national State of America’s Lakes report, or all Arizona lakes.

Cite this report: LakeQuality, “The State of Arizona’s Lakes 2026,” lakequality.org/report/az.