• 5,270 large dams blocked rivers in 1950
  • 36,500 large dams block rivers today
  • 17 percent of U.S. rivers are currently dammed
  • 600,000 miles of rivers in the U.S. have been impounded behind dams
  • 235,000 miles of rivers in the U.S. have been channelized
  • 25,000 miles of rivers in the U.S. have been dredged for navigation
  • 80 percent of river water in California is used for irrigation
  • 87 percent of river water in Arizona is used for irrigation
  • 25 percent of U.S. dams are older than their life expectancy of 50 years

Sources:
1, 2 — World Resources Institute
3-7 — American Rivers

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