Touchet River salmonid populations (including tributaries). The Touchet River originates in the Blue Mountains and terminates in the Walla Walla River near the town of Touchet. The Touchet River drains a majority of the northern portion of the Walla Walla watershed (~740 square miles). The mainstem is primarily formed by two major forks (North and South Forks of the Touchet River) and Patit Creek that converge near the town of Dayton, WA. Smaller tributaries including Whiskey and Coppei Creeks also originate in the Blue Mountains and terminate in the mainstem near Waitsburg, WA. The remaining tributaries downstream of Waitsburg originate in agricultural areas within the Palouse Islands or Pleistocene Lake Basins of the Columbia Plateau.