Risky reservoirs: California counties where aging dams pose the greatest threat

Canva

- Total high-hazard dams: 35
- Number potentially dangerous: 1 (2.9%)
- Potentially dangerous dams include:
--- 1 condition withheld

#49. Sonoma County
Canva

- Total high-hazard dams: 36
- Number potentially dangerous: 2 (5.6%)
- Potentially dangerous dams include:
--- 1 in poor condition
--- 1 condition withheld

#48. Napa County
Canva

- Total high-hazard dams: 12
- Number potentially dangerous: 1 (8.3%)
- Potentially dangerous dams include:
--- 1 in poor condition

#47. San Mateo County
Canva

- Total high-hazard dams: 24
- Number potentially dangerous: 2 (8.3%)
- Potentially dangerous dams include:
--- 2 condition withheld

#46. Contra Costa County
Canva

- Total high-hazard dams: 44
- Number potentially dangerous: 4 (9.1%)
- Potentially dangerous dams include:
--- 1 posing immediate threat
--- 3 in poor condition

#45. San Diego County
Canva

- Total high-hazard dams: 10
- Number potentially dangerous: 1 (10.0%)
- Potentially dangerous dams include:
--- 1 condition withheld

#44. Marin County
Uladzik Kryhin // Shutterstock

- Total high-hazard dams: 26
- Number potentially dangerous: 3 (11.5%)
- Potentially dangerous dams include:
--- 1 in poor condition
--- 2 condition withheld

#43. Santa Clara County
Canva

- Total high-hazard dams: 15
- Number potentially dangerous: 2 (13.3%)
- Potentially dangerous dams include:
--- 2 condition withheld

#42. Mendocino County
Canva

- Total high-hazard dams: 37
- Number potentially dangerous: 5 (13.5%)
- Potentially dangerous dams include:
--- 1 in poor condition
--- 4 condition withheld

#41. Orange County
Canva

- Total high-hazard dams: 14
- Number potentially dangerous: 2 (14.3%)
- Potentially dangerous dams include:
--- 2 in poor condition

#40. Solano County
Canva

- Total high-hazard dams: 14
- Number potentially dangerous: 2 (14.3%)
- Potentially dangerous dams include:
--- 2 condition withheld

#39. Lake County
Canva

- Total high-hazard dams: 45
- Number potentially dangerous: 7 (15.6%)
- Potentially dangerous dams include:
--- 1 in poor condition
--- 1 not rated
--- 5 condition withheld

#38. Riverside County
Canva

- Total high-hazard dams: 36
- Number potentially dangerous: 6 (16.7%)
- Potentially dangerous dams include:
--- 1 not rated
--- 5 condition withheld

#37. San Bernardino County
Canva

- Total high-hazard dams: 81
- Number potentially dangerous: 14 (17.3%)
- Potentially dangerous dams include:
--- 1 in poor condition
--- 13 condition withheld

#36. Los Angeles County
Canva

- Total high-hazard dams: 10
- Number potentially dangerous: 2 (20.0%)
- Potentially dangerous dams include:
--- 2 condition withheld

#35. San Luis Obispo County
Canva

- Total high-hazard dams: 15
- Number potentially dangerous: 4 (26.7%)
- Potentially dangerous dams include:
--- 1 in poor condition
--- 3 condition withheld

#34. Ventura County
Canva

- Total high-hazard dams: 11
- Number potentially dangerous: 3 (27.3%)
- Potentially dangerous dams include:
--- 3 condition withheld

#33. Kern County
Canva

- Total high-hazard dams: 9
- Number potentially dangerous: 3 (33.3%)
- Potentially dangerous dams include:
--- 1 posing immediate threat
--- 2 condition withheld

#32. Modoc County
Canva

- Total high-hazard dams: 20
- Number potentially dangerous: 7 (35.0%)
- Potentially dangerous dams include:
--- 7 condition withheld

#31. El Dorado County
Canva

- Total high-hazard dams: 5
- Number potentially dangerous: 2 (40.0%)
- Potentially dangerous dams include:
--- 1 in poor condition
--- 1 condition withheld

#30. Monterey County
Canva

- Total high-hazard dams: 14
- Number potentially dangerous: 6 (42.9%)
- Potentially dangerous dams include:
--- 6 condition withheld

#29. Santa Barbara County
StephanieFarrell // Shutterstock

- Total high-hazard dams: 20
- Number potentially dangerous: 9 (45.0%)
- Potentially dangerous dams include:
--- 9 condition withheld

#28. Tuolumne County
Canva

- Total high-hazard dams: 6
- Number potentially dangerous: 3 (50.0%)
- Potentially dangerous dams include:
--- 3 condition withheld

#27. Siskiyou County
Canva

- Total high-hazard dams: 6
- Number potentially dangerous: 3 (50.0%)
- Potentially dangerous dams include:
--- 1 in poor condition
--- 2 condition withheld

#26. Inyo County
Canva

- Total high-hazard dams: 26
- Number potentially dangerous: 13 (50.0%)
- Potentially dangerous dams include:
--- 1 in poor condition
--- 12 condition withheld

#25. Calaveras County
Canva

- Total high-hazard dams: 15
- Number potentially dangerous: 8 (53.3%)
- Potentially dangerous dams include:
--- 8 condition withheld

#24. Plumas County
Canva

- Total high-hazard dams: 9
- Number potentially dangerous: 5 (55.6%)
- Potentially dangerous dams include:
--- 5 condition withheld

#23. Alpine County
Canva

- Total high-hazard dams: 16
- Number potentially dangerous: 9 (56.3%)
- Potentially dangerous dams include:
--- 1 not rated
--- 8 condition withheld

#22. Mono County
Canva

- Total high-hazard dams: 12
- Number potentially dangerous: 7 (58.3%)
- Potentially dangerous dams include:
--- 7 condition withheld

#21. Amador County
Canva

- Total high-hazard dams: 5
- Number potentially dangerous: 3 (60.0%)
- Potentially dangerous dams include:
--- 3 condition withheld

#20. San Benito County
Canva

- Total high-hazard dams: 24
- Number potentially dangerous: 15 (62.5%)
- Potentially dangerous dams include:
--- 1 not rated
--- 14 condition withheld

#19. Fresno County
Canva

- Total high-hazard dams: 14
- Number potentially dangerous: 9 (64.3%)
- Potentially dangerous dams include:
--- 9 condition withheld

#18. Sacramento County
Canva

- Total high-hazard dams: 3
- Number potentially dangerous: 2 (66.7%)
- Potentially dangerous dams include:
--- 2 condition withheld

#17. Tulare County
Canva

- Total high-hazard dams: 3
- Number potentially dangerous: 2 (66.7%)
- Potentially dangerous dams include:
--- 2 condition withheld

#16. Sierra County
Canva

- Total high-hazard dams: 27
- Number potentially dangerous: 18 (66.7%)
- Potentially dangerous dams include:
--- 1 in poor condition
--- 1 not rated
--- 16 condition withheld

#15. Placer County
Canva

- Total high-hazard dams: 17
- Number potentially dangerous: 12 (70.6%)
- Potentially dangerous dams include:
--- 1 in poor condition
--- 11 condition withheld

#14. Butte County
Canva

- Total high-hazard dams: 11
- Number potentially dangerous: 8 (72.7%)
- Potentially dangerous dams include:
--- 8 condition withheld

#13. Madera County
Canva

- Total high-hazard dams: 4
- Number potentially dangerous: 3 (75.0%)
- Potentially dangerous dams include:
--- 1 not rated
--- 2 condition withheld

#12. Colusa County
Canva

- Total high-hazard dams: 8
- Number potentially dangerous: 6 (75.0%)
- Potentially dangerous dams include:
--- 6 condition withheld

#11. Merced County
Canva

- Total high-hazard dams: 24
- Number potentially dangerous: 18 (75.0%)
- Potentially dangerous dams include:
--- 1 in poor condition
--- 1 not rated
--- 16 condition withheld

#10. Shasta County
Canva

- Total high-hazard dams: 26
- Number potentially dangerous: 20 (76.9%)
- Potentially dangerous dams include:
--- 20 condition withheld

#9. Nevada County
Gibson Outdoor Photo // Shutterstock

- Total high-hazard dams: 5
- Number potentially dangerous: 4 (80.0%)
- Potentially dangerous dams include:
--- 4 condition withheld

#8. Trinity County
Canva

- Total high-hazard dams: 10
- Number potentially dangerous: 8 (80.0%)
- Potentially dangerous dams include:
--- 8 condition withheld

#7. San Joaquin County
Canva

- Total high-hazard dams: 6
- Number potentially dangerous: 5 (83.3%)
- Potentially dangerous dams include:
--- 5 condition withheld

#6. Imperial County
Canva

- Total high-hazard dams: 6
- Number potentially dangerous: 5 (83.3%)
- Potentially dangerous dams include:
--- 5 condition withheld

#5. Yuba County
Canva

- Total high-hazard dams: 7
- Number potentially dangerous: 6 (85.7%)
- Potentially dangerous dams include:
--- 6 condition withheld

#4. Mariposa County
Canva

- Total high-hazard dams: 1
- Number potentially dangerous: 1 (100.0%)
- Potentially dangerous dams include:
--- 1 in poor condition

#3. Humboldt County
Canva

- Total high-hazard dams: 1
- Number potentially dangerous: 1 (100.0%)
- Potentially dangerous dams include:
--- 1 condition withheld

#2. Tehama County
CL Shebley // Shutterstock

- Total high-hazard dams: 1
- Number potentially dangerous: 1 (100.0%)
- Potentially dangerous dams include:
--- 1 condition withheld

This story features data reporting by Paxtyn Merten, writing by Dom DiFurio, and is part of a series utilizing data automation across 50 states.

#1. Glenn County
Unwind // Shutterstock