Bitterroot Valley Irrigation 101 This is a complicated subject, with many moving parts but here's an overview: The irrigation water in the Bitterroot Valley is primarily managed by local irrigation districts and water user associations, with oversight and regulation from state and federal agencies. There are several irrigation districts in the Bitterroot Valley, including the Bitter Root Irrigation District, the Darby Irrigation District, and the Corvallis Irrigation District. These district...