Official Government Website

Idaho Water Facts

  • State Water Surface Area – 880 Square Miles
  • Number of Lakes – More than 2,000 — 1,228 of which have been named
  • Largest Lake – Pend Oreille — 148 Square Miles
  • Deepest Lake – Pend Oreille — sounded to a depth of 1,140 feet
  • Highest Waterfall – Big Fiddler Creek, South Fork Boise River — 600 feet
  • Miles of Streams and Rivers – 93,000 miles
  • Number of Named Streams and Rivers – 8,941 plus 1,478 named springs
  • Longest River – Snake River — 779 miles from entry at the Wyoming border to exit at Washington border.
  • Average Annual Precipitation – Varies from less than 10 to more than 60 inches.
  • Most Precipitation in 24-Hour Period – 7.7 inches of rain — Rattlesnake Creek in 1909
  • Annual Stream Inflow to State – About 37 million acre-feet
  • Annual Stream Outflow from State – About 75 million acre-feet
  • Irrigated Area of State – 3.3 million acres — of which about 3.0 million is irrigated from the Snake River system.
  • Highest Dam – Dworshak, North Fork Clearwater — 717 feet
  • Active Reservoir Storage Capacity – 12,384,000 acre-feet
  • Largest Active Storage Reservoir – Dworshak — 2,016,000 acre-feet
  • Snake Plain Aquifer Storage – Top 100 feet of aquifer — about 100 million acre-feet
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