The Walla Walla River is a tributary of the Columbia River, joining the Columbia just above Wallula Gap in southeastern Washington in the United States. The river flows through Umatilla County, Oregon, and Walla Walla County, Washington. Its drainage basin is 1758sqmi in area.CourseThe headwaters of the Walla Walla River lie in the Blue Mountains of northeastern Oregon. The river originates as the North and South Forks of the Walla Walla River. The surrounding forested land holds a network of hiking and mountain-biking trails.The confluence of the North and South Forks lies east of Milton–Freewater, Oregon. The river flows eastward to reach Milton–Freewater, which is built along its banks, and then flows northward through Milton–Freewater. Irrigation water is drawn from the river here and at numerous locations along the river.The Walla Walla River flows southwest of the city of Walla Walla in the Walla Walla valley. Mill Creek, which flows through the city of Walla Walla, joins the Walla Walla River at the Whitman Mission west of the city of Walla Walla.The Touchet River joins the Walla Walla at the town of Touchet, Washington. The annual mean discharge of the Walla Walla River just below the Touchet River confluence is 1212cuft/s. The maximum recorded discharge was 20300cuft/s in 1964.
