The Potholes are the defining geologic feature near this eastern Washington park. A series of Ice Age flood-carved depressions in the earth, combined with the dynamics of the O’Sullivan Dam, created hundreds of tiny islands surrounded by “pothole” lakes.
These little lakes make up half the O’Sullivan Reservoir, and Potholes State Park lies on the other side, where visitors find the lakes deeper and welcoming to boaters, fishers and swimmers.
The year-round fishing at Potholes is superb, with abundant yellow perch, crappie, largemouth bass, rainbow trout and walleye. But if you would rather be in the water on a hot, eastern Washington day, swimming and water sports abound. Think waterskiing, kayaking and paddleboarding.
More into birding than fishing? Fill your field journal on a visit to the Potholes lakes and islands. Sandhill cranes and waterfowl come through in late February; raptors in April; sage thrasher, lark sparrow and burrowing and long-eared owls arrive in May, along with shorebirds. When water levels drop in August, the mud flats beckon sandpipers, stilts, plovers and curlews.
If you have a sleeping bag, eastern Washington is the place to sleep under the stars, or you can rent a cute cabin in the primitive campground. Either way, you’ll have fun and learn about natural history and geology at this fascinating park.
Potholes State Park is a 773-acre camping park with 6,000 feet of freshwater shoreline on O'Sullivan Reservoir. This body of water is often confused with the Pothole Lakes themselves, which are a 30- to 45-minute drive from the park. The terrain is desert with freshwater marshes.
Use our interactive ADA recreation map to search for other state parks with ADA amenities and facilities.
Picnic & day-use facilities
The park provides three picnic shelters with four tables each, plus 73 unsheltered picnic tables in a lawned, well-shaded area. All day-use facilities are first come, first served. Restrooms are available in the day-use area, located on the banks of the reservoir.
3 miles of hiking trails
Water activities & features
60 feet of dock
Fish cleaning station
Personal watercraft use
Watercraft launches (4)
Other activities & features
Volleyball fields (2)
Volleyball players must bring their own equipment.
A recreational license is required for fishing and shellfish harvesting at Washington state parks. For regulations, fishing season information, or to purchase a recreational license, visit the Washington Department of Fish and Wildlife.
Located in Grant County on Potholes Reservoir, the park offers four watercraft launches and 60 feet of dock. Water levels in O'Sullivan Reservoir (Potholes Reservoir) fluctuate dramatically from spring to fall.
Launching a boat at a state park requires one of the following: • An annual launch permit (Natural Investment Permit); or • An annual Discover Pass and a daily launch permit; or • A one-day Discover Pass and a daily launch permit.
A daily watercraft launching permit for $7 and a trailer dumping permit for $5 is available at the park. Annual permits also may be purchased at State Parks Headquarters in Olympia, at region offices, online, and at parks when staff is available.
Latitude: 46º 58' 41.16" N (46.9781) Longitude: 119º 20' 52.08" W (-119.3478)
The park has 61 standard campsites, 60 full-hookup sites, five cabins, one dump station, four restrooms (two ADA), and four showers (two ADA).
Any tent or RV may use either site type. But, anyone using the full-hookup sites will pay that site fee. Maximum site length is 50 feet (limited availability). There is no camping next to the reservoir.
Check-in time is 2:30 p.m.
Check-out time is 1 p.m.
The park provides a group camp that accommodates up to 50 people. The group camp has a grassy section and is well-shaded. Facilities include a covered picnic shelter. Restroom facilities are nearby. There is a year-round creek adjacent to the group camp that provides excellent trout and bass fishing. Fees vary with size of the group.
The five cabins at Potholes are located in the primitive camp area, within a short walk of the Potholes Reservoir. Restrooms are nearby in the park, cabins have no plumbing and indoor cooking is prohibited. Each cabin has an AC outlet, ceiling fan and heating / air conditioning unit. Outside is a fire ring with attached grill. Pets are allowed in cabin 62 with a $15 (plus tax) pet fee per night. For more information, visit our cabins and yurts page.
Reservations & fees
Reservations can be made online or by calling (888) CAMPOUT or (888) 226-7688. For fee information, check out our camping rates page.
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.