The North Santiam watershed covers 1,529 square miles in western Oregon, primarily in the Cascade Range. The hydrology of the watershed is driven by the high precipitation in the winter months, with snowpack accumulation providing a significant portion of the water supply. The snowpack is closely monitored by the Natural Resources Conservation Service, with data on snow water equivalent available online. Surface water in the watershed is primarily composed of the North Santiam River, which flows for 92 miles before joining the Santiam River. The river is used for recreation, drinking water supply, and irrigation. Detroit Lake is the largest reservoir in the watershed, created by the Detroit Dam. The watershed experiences a Mediterranean climate, with wet winters and dry summers. Climate change is expected to increase the frequency and severity of droughts in the region.