The Columbia Plateau Aquifer system is a series of layered aquifers across ~44,000 mi2 of Washington, Oregon, and Idaho. The aquifer system is on the Columbia Plateau, contained within the Cascades, Rocky Mountains, Okanogan Highlands, and the Blue Mountains. These aquifers are bounded on the bottom by a layer of Miocene basaltic rock that can be up to 15,000 ft thick. The primary aquifers in the system are shallow, and unconfined.
