(yăk'əmô, –mə), river, 203 mi (327 km) long, rising in the Cascade Range, central Wash., and flowing SE past Yakima to the Columbia River near Kennewick. The U.S. Bureau of Reclamation's Yakima project (begun in 1906) utilizes the Yakima and its tributaries to irrigate c.460,000 acres (186,160 hectares) and has helped make the river valley an important farming and fruit-growing region. A major unit of the project is the Keechelus Dam (completed 1917).