As winter turns to spring, the McKenzie River flows toward Eugene with impressive force. While powerful, the river is not invincible — in fact, snow-fed rivers with slow drainage systems like the McKenzie are more susceptible to the effects of climate change than other kinds of river systems, according to a new study out of OSU in Corvallis.
Rivers like the McKenzie in the high Cascades water system are more vulnerable to climate change partly because of the unique geological formations in the Cascades. According to Gordon Grant, a fluvial geomorphologist with the Forest Service and co-author of the study, McKenzie Pass in the Cascades Range serves as a good example because its lava flows are full of fractures and holes.
Melted snow or rain that seeps into the porous rock at McKenzie Pass takes longer to reach a non-permeable surface, and after that, it is slowed even more by a lack of steepness. “It’s basically the same thing as if you were on a bicycle,” Grant says. “If you were going downhill and it wasn’t steep, you wouldn’t go as fast.”
This slowness allows the water to gradually flow into river systems, lasting into late summer. The study looked at 81 watersheds over a 60-year period and determined that river systems with less steepness and more permeability will see diminished late summer flows as the climate warms.
But this doesn’t mean the water will disappear anytime soon; in fact, Grant says these kinds of groundwater systems allow Oregon to have more water than other places. “But if you follow this idea that slow, snow-fed systems will lose the most water in the late season, we’ll have less water than we have now,” Grant says. This could affect water uses, including power generation, irrigation and fish survival.
This information probably won’t spur much action to slow climate change, according to a recent Oregon Sea Grant survey. The online survey polled 348 Oregon coast leaders, and while 60 percent of them acknowledged that climate change is happening, and most believe that their professional efforts toward addressing climate change would benefit the community, it was ranked less of a concern than a floundering economy or a tsunami threat.