Updated August 2026
The State of Arizona's Lakes 2026
Of 73 lakes in Arizona, 28.6% sit in EPA's favourable condition classes for nutrients and algae and 28.6% in its poorer ones. Ak-Chin Reservoir is the cleanest; 19 lakes (26%) are on an official impaired-waters list.
Data Report
73
Monitored lakes sampled
C
Average readings
28.6%
low nutrient and algae readings
26%
On impaired list
Arizona nutrient and algae readings
Cleanest lakes in Arizona
Cleanest combined nutrient and algae readings, 2026.
- 1.Ak-Chin Reservoir — Pinal County28 µg/L P · 4 µg/L chl-a
- 2.Sunris Park Lake — Yuma County99 µg/L P
Highest measured algae
Highest measured chlorophyll-a (algae) concentration.
No qualifying lakes with sufficient data.
Trending lakes
Improving
- 1.Chaparral Park Lake — Maricopa County
- 2.Ak-Chin Reservoir — Pinal County
- 3.Lakeside Lake — Pima County
- 4.Woods Canyon Lake — Coconino County
- 5.Willow Creek Reservoir — Yavapai County
- 6.Lynx Lake — Yavapai County
- 7.Show Low Lake — Navajo County
- 8.Ashurst Lake — Coconino County
Declining
- 1.Sunris Park Lake — Yuma County
- 2.Canyon Lake — Maricopa County
- 3.Rose Canyon Lake — Pima County
- 4.Tempe Town Lake — Maricopa County
- 5.Saguaro Lake — Maricopa County
- 6.Pena Blanca Lake — Santa Cruz County
- 7.Whitehorse Lake — Coconino County
- 8.Fool Hollow Lake — Navajo County
Impaired waters in Arizona
19 lakes appear on the EPA/state 303(d) impaired-waters list (13 formally listed, 7 with a cleanup plan/TMDL).
Mercury · 12Oxygen depletion (low DO) · 6pH / acidity · 6Nutrients (phosphorus, nitrogen) · 5Ammonia · 2Noxious aquatic plants · 1Metals (other than mercury) · 1
Explore Arizona lakes
Readings combine total phosphorus, total nitrogen, chlorophyll-a, and turbidity 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”.