Montage of Washington State Park scenes
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Interpretation and history at Potholes

History

O'Sullivan Reservoir (Potholes Reservoir) was formed as a result of two major events, one natural and one man-made. Huge depressions (30 to 70 yards wide and 10 to 60 feet deep) were made in the earth during the Pleistocene flooding. Those depressions were filled with water (making "pothole" lakes) when the water table rose in the 1950s with the creation of O'Sullivan Dam. The dam was part of a project by the Bureau of Reclamation to provide irrigation water to farmers.

Interpretive opportunities

There are currently no interpretive opportunities at this park.