Potholes Reservoir

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.

Potholes Reservoir
Aerial view of Moses Lake & Potholes Reservoir, Washington 01A.jpg
Aerial view from the north (2009). Moses Lake is at lower left and the Potholes Reservoir at center.
LocationGrant County, Washington,
United States
Coordinates46°58′57″N 119°17′28″W / 46.98250°N 119.29111°W / 46.98250; -119.29111Coordinates: 46°58′57″N 119°17′28″W / 46.98250°N 119.29111°W / 46.98250; -119.29111[1]
Lake typeReservoir
Basin countriesUnited States
Average depth18 feet (5.5 m)[2]
Max. depth142 feet (43 m)[2]
Surface elevation1,043 feet (318 m)[1]

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. The potholes were initially carved out during the Pleistocene by flood waters originating from Glacial Lake Missoula.[3] Subsequent damming of the area by the Columbia Basin Project raised the water table high enough to allow these topographical depressions to become lakes.

Also known as:[1]

  • Moses Lake
  • O'Sullivan Reservoir
  • Mardon
  • Mardon Resort


On the shore of the reservoir is Potholes State Park, a 640-acre (2.6 km2) member of the Washington State Park System. It has 600 feet (180 m) of shoreline on the reservoir.[4]


There are many types of fish inside of the reservoir, including:


  1. ^ a b c d "Potholes Reservoir". Geographic Names Information System. United States Geological Survey. Retrieved 2009-05-03.
  2. ^ a b "Potholes Reservoir Research Management Plan" (PDF).
  3. ^ Alt, David; Hundman, Donald W. (1995). Northwest Exposures: A Geologic History of the Northwest. Missoula, Mont.: Mountain Press. ISBN 0-87842-323-0. OL 800810M.
  4. ^ "Potholes State Park". Washington State Parks and Recreation Commission. Archived from the original on February 9, 2015. Retrieved February 5, 2015.

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