Central Oregon's Geology And How It Affects Water Supply


How Volcanoes Affect the Basin

In the Deschutes River Basin, volcanic geology controls everything from channel shape to water temperature to summer flow levels. The volcanic rock in the region is also responsible for regulating the temperature and flow levels in the Deschutes River throughout the year. Because the rock is so porous, it absorbs a lot of rainfall and snowmelt, releasing it into the river at a slow rate over the course of the year from underground springs. The water from these springs stays at a nearly constant temperature and keeps a low level of flow (known as ‘baseflow’) in the Deschutes and its tributaries regardless of how much rainfall or snowmelt is occurring. These baseflows are very important for fish, especially those which depend on having cool pools to over-summer in (like steelhead).

Elevation Plays A Role

The Deschutes River is steep—dropping over 4,500 feet from its headwaters before reaching the Columbia River. For comparison, the Columbia River only drops 2,700 feet over its 1,200 mile length. This steep flow path gives the Deschutes a lot of erosive power, allowing it to cut into bedrock and form the many steep, deep canyons it travels through on its way to the Columbia.