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Colorado River Levels Will Drop Due To Climate Change. What Does That Mean For You?

Southern Nevada Water Authority
The Colorado River empties into Lake Mead outside Las Vegas, Nevada. The key reservoir is only 40 percent full.

The Colorado is undeniably the most important river in the American Southwest.

“Every major city gets water out of this basin. 40 million people, seven states, two nations, 22 federally recognized Indian tribes -- everybody depends on it,” said Brad Udall, senior water and climate research scientist at Colorado State University.

According to a new study by Udall and Jonathan Overpeck, a climatologist at the University of Arizona, this essential river is seeing its water levels drop due to climate change.

The researchers contrasted the most recent drought on the river -- from 2000 to 2014 -- with another one from the mid-1950s to about 1967. The earlier drought's primary cause was a sharp fall in precipitation. In the most recent drought, however, the primary factor was heat.

“Since 2000, the Colorado River has been in a drought. The flows are down about 20 percent. We say that about a third of that reduction is due to the higher temperatures that we are now experiencing in the 21st century,” Udall said.

Since 2000, temperatures have risen on average 1.6 degrees Fahrenheit above normal in the Upper Colorado River Basin annually. Udall and Overpeck found that the hotter weather stripped the river of at least 500,000 acre-feet of water. That’s enough water for half a million families of four for a year according to the U.S. Bureau of Reclamation.

Where is the water going? Into the atmosphere, ecosystem and human consumption and agriculture.

“We now have snowmelt two to three weeks earlier, so you have a longer period of time for plants to use water, you have hotter conditions so the plants use more water and the atmosphere as the climate warms demands more water. It’s a bigger suck, if you will, for moisture,” Udall said.   

The researchers predict that as weather continues to warm over the next three decades, the water in the Colorado River will decline by about a quarter. That would be a dramatic impact on a river that supplies water to 40 million people in seven western states, including Colorado. By the end of this century, the river could drop by more than half, far more than federal water managers have predicted.

"Over 60 percent of all the water taken from the Colorado River is used for agriculture."

But some scientists aren’t so sure.

“So this is my question: is this drought, are we going to recover, is it climate change and we’re not going to recover, how much of each -- the paper doesn’t quite address that. It certainly doesn’t do the science to get at the bottom of it,” said Martin Hoerling, a research meteorologist specializing in climate dynamics at NOAA's Earth System Research Laboratory in Boulder, Colorado. He was not involved in the study.

“That’s a big deal. Now, I’m saying this like it’s a certainty -- it’s not. But the aggregate, the average, of all the models do indicate a wetter climate,” Hoerling said. “Why? Well it may simply be the water vapor content is going to be more abundant, so when storms come they will be able to bear more moisture and when they drop that moisture there will be more snowpack as a result in the core of winter in the upper Colorado River Basin. That effect is enough to compensate for most of the warming.”

Demand for Colorado River water continues to grow

No matter the outcome, Hoerling and Udall agree, the demands for the river’s water have never been higher. Currently, the Colorado River and its tributaries are the lifeblood for at least 22 tribes, seven national wildlife refuges, four national recreation areas, 11 national parks and 5.5 million acres of agricultural land.

It’s also a major water source for the growing Front Range and metro Denver areas due to the Colorado-Big Thompson Project. According to Northern Water, the project collects and delivers, on average, more than 200,000 acre-feet of water each year. Most of this water is the result of melting snow in the Upper Colorado River Basin west of the Continental Divide. The project transports the water to the East Slope via the 13.1-mile Alva B. Adams Tunnel beneath the Continental Divide. The water is collected and distributed via 12 reservoirs, 35 miles of tunnels and 95 miles of canals.

“Whether it’s climate change that we are confronting, or whether it’s another drought that is inevitably going to happen again, we have to build up more resiliency to be able to work our way through the next event, and we weren’t challenged in that same way 50 years ago, as we are going to be challenged in the next 50 years,” Hoerling said.

Credit Southern Nevada Water Authority
Southern Nevada Water Authority
The infamous 'bathtub ring' at Lake Mead in Nevada.

Downstream in southern Nevada, they are investing heavily for their future water needs.

“We have banked over eight years of our current demands in our regional banks in our aquifer here, that’s banking with our partners in Arizona, California and even the country of Mexico,” said John Entsminger, the general manager of the Southern Nevada Water Authority.

"We can solve it as a state, as a nation, as a world by reducing greenhouse gas emissions. We're making progress on this. We're not doing nearly enough."

It’s his job to make sure that the desert oasis of Las Vegas has water. Lake Mead, which gets most of its water from the Colorado River and is the key reservoir for the valley, has dropped steadily since it was almost full in 2000. Fast-forward 17 years and now it’s only 40 percent full.

The Southern Nevada Water Authority is on track to finish a whopping $1.5 billion infrastructure project that will provide a new intake into Lake Mead and pump station, and they’ve reduced Colorado River water consumption by about a third, even as the Las Vegas Valley population continues to grow.

“Las Vegas is real world example of how you can grow your economy and have a robust and dynamic community but also, at the same time, drastically reduce your overall water footprints,” Entsminger said.

Over 60 percent of all the water taken from the Colorado River is used for agriculture, according to the Bureau of Reclamation. Although practically none of the Colorado River water allocated to the Las Vegas valley is used for agriculture, Entsminger thinks that both municipal and agricultural sectors will need to be more mindful of their usage.

“That [change] is possible in the agricultural sector, but it will take substantial investment to grow more food using less water, but I think that’s the future of both urban and agricultural users in the Colorado River Basin is -- learning to do more with less water,” Entsminger said.   

Udall said that the future water loss they predicted in the study is not inevitable, but we need to act now.

“We actually can solve this problem,” he said. “We can solve it as a state, as a nation, as a world by reducing greenhouse gas emissions. We’re making progress on this. We’re not doing nearly enough.”