Climate Change Will Flood Oregon in the Winter and Dry Up Its Rivers in the Summer

It's fairly intuitive that climate change and rising temperatures will eventually reduce the amount of snow that falls in the mountains, and the amount of water that the melting snow becomes in the spring, but a new study done by Oregon State University scientists quantifies just how much less water the nearby rivers will get because of this. It could get pretty dramatic, pretty soon.

According to this research, published in Hydrology and Earth System Sciences, a temperature rise of 2˚C—which by all accounts it looks like we will blow right past by the middle of the century, the way efforts to reduce greenhouse gas emissions are going—will reduce the amount of water stored in the snowpack of the McKenzie River watershed by 56 percent.

The McKenzie River feeds into the Willamette River, draining part of the Cascade Range. The affect on the Willamette could be serious. Study lead author Eric Sproles points out:

Between 60-80 percent of summer stream flow comes from seasonal snow about 4,000 feet. As more precipitation falls as rain, there will be more chance of winter flooding as well as summer drought in the same season. More than 70 percent of Oregon's population lives in the Willamette Valley, with the economy and ecosystems depending heavily on this river.

In more detail, the study found that the average day of peak spring snowpack will be 12 days earlier by 2050. Mountains between roughly 3000 and 6000 feet will lose the most stored water, with some places going without snow for 80 fewer days per year on average compared to now. Elevations higher than 6000 feet also will see decreases in snow, but to a lesser degree. Though there are dams in the McKenzie River watershed whose operations could be changed to help manage the new water flow, this will not be able to make up for the loss of water stored in snowpack.

Why such a dramatic decrease in the amount of water stored in snowpack?

The report points out that in mountain ranges such as this, snowfall typically occurs at temperatures right around the freezing point. Just slight changes in temperature can tip the balance from frozen to liquid precipitation. Even if the area gets much more precipitation than it does now at the climate changes, it won't really increase the amount of water that gets stored as snow every year.

Though this study looked at one specific watershed, it has implications for many other places on the planet as well. Similar snowpack conditions exist wherever there are low altitude maritime mountains: Japan, New Zealand, Northern California, the Andes, Eastern Europe, and parts of the Alps at low elevation.