 The Columbia Basin Project in central Washington changed the character of Crab Creek substantially.The Crab Creek irrigation-return drainage basin covers an irrigated area of 296 mi² (767 km²).A large earthfill dam, the O'Sullivan Dam (also referred to as the "Potholes Dam") was constructed from 1947 to 1949, forming Potholes Reservoir, which serves as a central point in the CBP for storage of irrigation water, natural runoff, and irrigation-return flow, allowing irrigation water reuse throughout the southern CBP area.