There are approximately of irrigation-related canals and ditches in the lower basin of the Malheur River and its tributary Willow Creek. The streamflow of the Malheur and its tributaries is heavily influenced by a complex system of irrigation diversions, siphons, and canals, which begin near Malheur river mile 65, near Namorf and Harper, Oregon. This irrigation system extends downstream to the mouth of the Malheur at Ontario, Oregon. Irrigation is used on about within the Malheur River basin. The irrigation system is part of the Bureau of Reclamation's Vale Project, which includes a number of water impoundments, the largest of which are Warm Springs Reservoir on the mainstem Malheur River, Beulah Reservoir on the North Fork Malheur, Bully Creek Reservoir on Bully Creek, and Malheur Reservoir on Willow Creek. The project is operated and maintained by the Vale-Oregon Irrigation District.