Border Policy Brief
The Columbia River watershed comprises 258,500 square miles (about the size of Texas), with 15 percent of the watershed located in Canada. Tributaries in the upper watershed drain a substantial portion of the Canadian and American Rocky Mountains; precipitation and snowmelt from the Rockies are main flow components. The river then crosses the arid Columbia Plateau and reaches the Pacific via the Columbia River Gorge. In an average year, the river disgorges 198 million acre-feet (MAF) of water, with 25 percent of the runoff (a disproportionately large amount) originating in Canada. With snowmelt a large component of runoff, the river’s flow peaks in the May - July period; those three months typically account for over half of the natural annual runoff.
1 - Winter
Davidson, David L. and McClain, Jaymes, "The Columbia River Treaty Review: A Synopsis" (2014). Border Policy Research Institute Publications. 12.