The Columbia River has created regal gorges by cutting through the Cascades and the Coast Ranges; it is fed by the Cowlitz and Willamette rivers, which drain the Puget trough between those ranges. Grand Coulee, now a reservoir in the Columbia basin project, was a former stream channel of the Columbia River. It was created during the last ice age when the Columbia's course was blocked by ice, forcing it to cut a new channel through the Columbia Plateau. When the ice receded the river resumed its former channel.
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