It’s Getting Hot in Here, So Take Off All Your Certainty: Hot Drought as the New Norm for the Southwest — The Catalyst

Changing nature of Colorado River droughts, Udall/Overpeck 2017.

From The Catalyst (Emily Kressley):

Think about a restless night of sleep, where you toss and turn and wake up in a sweat. Not only are you uncomfortable, you’re also dehydrated — you reach for a big glass of water. And now think back to a big night out, where maybe you had one too many and you really need that glass of water, or several, to assuage that headache. In a similar fashion, our Earth is also overheating, wrapped in a blanket that traps warmth. Unfortunately for the Southwest, when it “sweats,” or evapotranspiration occurs, there is no glass of water by its bedside table. And when it’s really dehydrated, just one good winter isn’t going to solve the drought.

A 2017 study by Brad Udall and Jonathan Overpeck called “The Twenty-First Century Colorado River Hot Drought and Implications for the Future” published some terrifying news about the impacts of warming within the last century. Within your lifetime, you’ve experienced this warming in some capacity. If you’re based here in Colorado, you or your family likely remember what drought looked like in 2002 or 2012. The basis of the study is that the flow of the Colorado River was 19.3% below average 2000 to 2014, as compared to the 1906 to 1999 average, making it “the worst 15 year drought on record.”

It’s not a coincidence that news headlines have consistently ranked recent droughts at the top of the list. About one third of this flow loss comes from the unprecedented temperature rise: 0.9 degrees Celsius above the 1900s average. Yes, temperatures have risen before, but never so much, so fast. And there has never been a roaring civilization quite like our current society based in what should be a desert. “Previous comparable droughts were caused by a lack of precipitation, not high temperatures,” according to Udall and Overpeck.

The region’s hydrology is a mixed bag of modeling — we can’t be positive about what’s going to happen. But we are positive that warmer temperatures lead to a decline in stream flow. This decline can be linked to droughts that have lasted decades, rather than a single year. Coloradans, especially those who work in agricultural or ranching occupations, are familiar with drought and what it’s like to operate under a water deficit. But mega-droughts? This amount of uncertainty? Droughts that were previously classified as moderate are predicted to become more severe. That’s when your sleep gets restless.

Because the Earth is wrapped in a thick down comforter, rising temperatures and water scarcity are not isolated phenomena; they affect the entire system. When temperatures warm, the snowpack is diminished. Even if precipitation levels remained the same, the change to rain from snow removes the storage mechanism nature had in place. With rainfall occurring more frequently and earlier on in the year, the growing season starts prematurely, sucking up greater amounts of moisture from the soil. As a result, runoff is reduced and does not replenish already depleted reservoir levels. Increased temperatures also cause more water to evaporate from the soil, creating longer fire seasons. With diminished snowpack and reduced runoff, the hottest months of the summer become even drier, intensifying drought effects.

The study predicts that as warming continues to increase at its current rate, there will be a 20–30% flow loss by mid-century, and a 35–55% loss by the end of the century. And while the Colorado River reservoir system can store four times the annual flow of the river, longer droughts and higher demands in these periods will deplete that quickly, according to Udall and Overpeck. To put this into perspective, 40 million people rely on the river in seven different states for their survival. If we were to cut the water supply in half and only serve 20 million people, 3.5 times the population of the entire state of Colorado would be left dry, according to Bureau of Reclamation. That’s almost 263 packed Denver Broncos stadiums, accordig to Empower Field at Mile High. And as we’ve seen in 2019, one good year is not going to solve the issue — much of the state is now back in a drought. If water levels drop too low in Lake Powell and Lake Mead, imperative storage reservoirs, the hydropower turbines will no longer be effective. Energy prices will skyrocket, as will the risk of a compact call, which is a restriction on water consumption in the Upper Basin until the lower basin water allocations are delivered.

We know that temperatures are rising, water levels are decreasing, and risk and uncertainty are mounting. While the future looks grim, there is still time to avoid the worst by ringing the alarm and staying politically active. Talk about how climate change is personally affecting us now with friends and family, stay up to date on the news, put pressure on your state’s representatives. Drought contingency negotiations have already been in the works, with the 2007 interim guidelines slated for revision in 2026. We’ve seen drought before, and we’ll see it again. Climate change is water change, and while it’s a phenomenon bigger than any of us, we are not powerless in combatting it.

Emily Kressley
Emily, class of 2020, is an environmental policy major originally from Essex, Conn. While she is drawn to Colorado for its mountains and skiing, she has found strong communities within the CC Cutthroat rugby team, Kappa Kappa Gamma sorority and, of course, The Catalyst staff.

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