The Potholes Reservoir is part of the Columbia Basin Irrigation Project. It is formed by the O'Sullivan Dam and located in central Washington, in the United States. The reservoir is fed by water from Moses Lake, part of the Crab Creek basin.The area features several lakes (typically 30-70 yards wide and 10–30 feet deep). These lakes, known as "potholes" were created through both natural and man made processes.