Merwin Dam

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Merwin Dam
Location Clark / Cowlitz counties, Washington, USA
Coordinates 45°57′24″N 122°33′18″W / 45.95667°N 122.55500°W / 45.95667; -122.55500Coordinates: 45°57′24″N 122°33′18″W / 45.95667°N 122.55500°W / 45.95667; -122.55500
Construction began 1929
Opening date 1931[1]
Operator(s) Pacificorp[1]
Dam and spillways
Impounds Lewis River
Height 313 feet (95 m)
Length 1,250 feet (381 m)[1]
Creates Lake Merwin
Total capacity 422,000 acre feet (0.521 km3)[1]
Catchment area 731 square miles (1,890 km2)[1]
Surface area 3,921 acres (15.9 km2)[1]
Power station
Commission date 1931/1949/1958
Turbines 3 x 45 MW Francis-type, 1 x 1 MW[2]
Installed capacity 136 MW
Annual generation 511,534 MWh

Merwin Dam (also known as Ariel Dam[3]) is a concrete arch gravity-type hydroelectric dam on the Lewis River, in the U.S. state of Washington. It is located on the border between Cowlitz County and Clark County. Its reservoir is called Lake Merwin.

On November 24, 1971, the dam was fully lit allegedly giving the skyjacker D. B. Cooper an identifiable landmark when he jumped from a Boeing 727 passenger liner. Cooper had ransomed 200,000 dollars from Federal Authorities after holding hostage the 727 and its passengers in Seattle.[4]


  1. ^ a b c d e f Merwin Dam Archived 2011-07-16 at the Wayback Machine., NPDP Dam Directory
  2. ^ "Merwin Hydroelectric Project" (PDF). Final License Application. PacifiCorp. Retrieved 10 May 2012. 
  3. ^ U.S. Geological Survey Geographic Names Information System: Merwin Dam
  4. ^ In Search Of..."D. B. Cooper" hosted by Leonard Nimoy, produced by Alan Landsburg c. 1979