Overview
Potholes Reservoir is a large Columbia Basin Project storage and regulating reservoir in Grant County, Washington, formed by O'Sullivan Dam and operated by the U.S. Bureau of Reclamation. At full pool it covers on the order of 28,000 acres of flooded scabland potholes, islands, and open water south of Moses Lake. O Sullivan Dam closes a scabland basin that fills with Columbia Basin Project water and Crab Creek inflow.
Average depth is roughly 18 feet with deeper holes near 140 feet. Irregular basalt shoreline, flooded coulees, and countless islands create one of the most distinctive reservoir landscapes in the Northwest. Countless basalt islands and flooded coulees create a maze that rewards local knowledge when the pool is down.
The reservoir is a major destination for walleye, bass, and waterfowl hunting/fishing under Washington Department of Fish and Wildlife rules. Potholes State Park, WDFW wildlife areas, and public ramps provide access. Potholes State Park and surrounding wildlife areas are among Grant County busiest outdoor destinations.
Water levels are managed for irrigation storage and Columbia Basin Project operations, with a full-pool elevation near 1,047 feet. Elevations can change with irrigation demand and inflows from Moses Lake, so monitoring current lake levels is important for boating among the islands and for shoreline access. Irrigation deliveries and return flows can move elevations through the growing season even without major storms.
Current Conditions
Potholes Reservoir is currently 16.79 feet below full pool and has been falling over the past week.
- 7-day trendFallingLatest movement can differ from the seven-day trend.
- 7-day changeDown 1.30 ft
- 30-day changeDown 6.18 ft
- Drought conditionsModerate Drought
About This Lake
Learn how this lake is managed, what affects its water level, and where Lake Insights gets its data.
Potholes Reservoir is a 27,800-acre reservoir on the Crab Creek managed by U.S. Bureau of Reclamation (Columbia Basin Project, O'Sullivan Dam).