The Umatilla River Basin is located in the northeastern part of Oregon, in the Middle Columbia Basin, occupying approximately 2,500 square miles. The Umatilla River originates in the conifer forests of the Blue Mountains at over 6,000 feet elevation and flows west and then northwest through the semi-arid shrub steppe of the Deschutes-Umatilla plateau, entering the Columbia river at an elevation of 270 feet above sea level. This confluence occurs at the town of Umatilla, Oregon, about 300 miles upstream from the Pacific Ocean. The Umatilla Basin is home to productive agricultural and forestlands and contains streams with historically viable and returning salmonid populations.
TMDL approved by EPA on Sept. 29, 2005
TMDL approved by EPA on Feb. 19, 2007