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Lake Lewis Chapter: Information about Lake Lewis

Lake Lewis formed from hydraulic damming of flood waters behind Wallula Gap along the Horse Heaven Hills, in the state of Washington. The water remained for only a week or less before all the flood waters drained through Wallula Gap, just southeast of the Tri-Cities area.

Lake Lewis reached a maximum elevation of about 1200' above sea level (today's sea level) before quickly subsiding. Lake Lewis also backflooded and filled the Yakima and Walla Walla Valleys.

Maximum extent of Lake Lewis Maximum extent of Lake Lewis Maximum extent of Lake Lewis Maximum extent of Lake Lewis Maximum extent of Lake Lewis Maximum extent of Lake Lewis Maximum extent of Lake Lewis
The maximum extent of Lake Lewis. Image created by Bruce Bjornstad, a geologist and member of the Lake Lewis Chapter.

The image below shows the extent (depth) of flooding in the Tri-Cities area of Washington
while inundated by Lake Lewis at its maximum extent. The image was also created by Bruce Bjornstad.

Tri-Cities during flood maximum Tri-Cities during flood maximum Tri-Cities during flood maximum Tri-Cities during flood maximum Tri-Cities during flood maximum Tri-Cities during flood maximum Tri-Cities during flood maximum

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updated Decmber 2003

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