Image: www.sierranevadaalliance.org

As of January, the Sierra Nevada snowpack is 80% below average. Even following one of the driest years in California’s history, this number is still shockingly low. In an Olympic sized pool this would be like only having one of five lanes to swim in. While it is understandable for California to be concerned with the depletion of the Sierra Nevada, recent research suggests we should be equally concerned about what lies ahead for the Colorado River.

The Colorado River Basin serves 30 million people in Arizona, California, Colorado, Nevada, New Mexico, Utah, Wyoming, and Mexico. It covers 190,000 square kilometers, 7 times the area of Massachusetts. Irrigating 4 million acres of agricultural land, and producing 10 billion kilowatt-hours of hydroelectric power yearly, it is an invaluable resource. But, with demand already exceeding supply and continuing climate change and variability (such as drought), the future of the basin is increasingly uncertain.

A recent study on the future of the Colorado River Basin by Darren Ficklin and colleagues modeled the future of the river in different climate scenarios. The results are alarming.

In the study, using a number of different computer models, Ficklin and colleagues assessed the natural cycles of water (snowmelt, evapotranspiration, surface runoff, subsurface runoff, and streamflow) in the Upper Colorado River Basin between the years 2050 and 2080. Ultimately, the computer simulations showed a change in water movements due to climate change impacts, which will decrease water availability by about 50% over the next 65 years.

Usually, when thinking about water availability the only concern is with the volume of water. Many forget to consider one of the most important aspects of availability: timing. Historically, in the Colorado River Basin, spring has had twice as much streamflow (1200 m3/s) as summer (600 m3/s). But Ficklin’s research suggests the overall streamflow during those pivotal months will decline by about 50% by 2080.

The situation is even more serious in the summer. According to the models, 22% of the stream flows of the Basin are going to decrease by 90% during the summer within the next 65 years. While not intuitive, this small reduction during the summer could be enough to alter ecosystems, with far-reaching effects.

The explanation for the change in timing was a shift in the melting of snow packs. Snow packs are projected to melt about 1-2 months earlier than in historical times. Earlier snowmelt means an earlier peak in the amount of water that is soaking into the soil, shifting the peak from May to April. Shifting the peak means there will be less water in the soil during the summer months when the vegetation needs it most.

What do these projections mean? They mean that by the year 2080 the western states and everyone else that relies on the Colorado River Basin will be in danger of not only running out of water, but major lifestyle changes as well. The effects of climate change on the Basin will not stop at a dwindling supply of drinking water. Water does a lot more for us than we think. Agriculture is one of its biggest consumers, and a decline in water availability would be dire for all those reliant on Southern California crops. Ecosystems are another major consumer, and a change in a habitat has a butterfly effect. A reduction in the amount of water available in an ecosystem could cause it to collapse.

So, what do we do? We focus on augmenting our water supply. On an individual level this means using conservation techniques like taking shorter showers and transforming your front lawns into desert landscapes. On a larger scale this means thinking about alternative sources of water like desalination, changing seawater into freshwater, or storing water in aquifers for later use. With these projections for the future of the Colorado River and the present reality of the Sierra Nevada snowpack, our focus needs to turn to increasing our water supply one drop at a time, in order to ensure our future.

Read Ficklin and his colleague’s study, “Climate Change Impacts on Streamflow and Subbasin-Scale Hydrology in the Upper Colorado River Basin,” published in PLOS ONE in August 2013.