As a mega-drought continues, new projections show that a major reservoir in the Colorado River could drop to a record low later this year

As a mega-drought continues, new projections show that a major reservoir in the Colorado River could drop to a record low later this year

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The cuts will be caused based on the terms of drought supply plans signed by the seven Colorado River Basin states in 2019 in an effort to stabilize the river system.

Despite the similarities, Lake Mead is only 39% full today. And Lake Powell, the second largest reservoir of the river, is only 36% full, according to an April water supply report.

The storage dams along the river system were created to serve as a buffer to store water and ensure a reliable supply, even in times of drought. But experts believe that due to climate change and a 20-year drought, more water is now being taken from the river system than flows into it, leading to declining levels in these major reservoirs.

“It shows us that the kind of dire scenarios we were preparing for and that we hope would not happen are now here,” said John Fleck, director of the Water Resources Program at the University of New Mexico.

The Colorado River supplies 40 million people living in seven western states and Mexico, and irrigates more than 5 million acres of farmland as it swings from the Rocky Mountains toward the Gulf of California.
The reduction in water supply that could take effect next year will be felt in Arizona, Nevada and Mexico, but Arizona will be hit hardest by the cuts, according to the provisions of the drought emergency plan signed by the three states. is, which contains the bottom bowl. . The upper wax states of Wyoming, Utah, Colorado and New Mexico have agreed to a separate plan calling for voluntary water conservation measures to prevent Lake Powell from also reaching critically low levels.
As part of the drought plan for the bottom line, the Central Arizona Project – a massive 336-mile canal and pipeline system that transports water in the Colorado River to Phoenix, Tucson and farms and towns in between – will see the water supply cut off by about one-third in 2022 due to its junior rights to the river’s water.
The effects of the water cuts will be felt most strongly on farms in central Arizona, due to their lower priority status in a complex level system used to determine who loses water first in the event of a shortage.
The Central Arizona Project Canal runs through the rural desert near Phoenix. Some farmers who receive Colorado River water from the Central Arizona Project may find that their deliveries are already being sharply cut next year.
In a joint statement last Thursday, the Arizona Department of Water Resources and the CAP acknowledged the new projections and impending cuts, but said the state was prepared.

“While the study is significant, it is not a surprise,” the statement said. “We are prepared for these conditions, thanks to Arizona’s unique collaborative efforts among water leaders, including tribes, cities, agriculture, industry and environmental organizations that have developed innovative conservation and mitigation programs as part of the implementation of the drought plan.”

One of the farmers who is seeing his water supplies reduced is Dan Thelander. Together with his son, brother and cousin, Thelander grows cotton, alfalfa and other crops on 6,500 acres in the desert of Pinal County, Arizona.

With less water expected to be available to him next year, Thelander said he will likely have to vomit 30 to 40% of his soil or leave it unsown.

Dan Thelander farms cotton, lucerne and other crops in the desert of Pinal County, Arizona. He, along with other farmers in the region, will see their supply of Colorado River water significantly reduced next year.

“We will have to lay off employees. We will not buy as much seed or fertilizer or tractors, and therefore we will only have to scale down and operate a smaller farm,” Thelander said. “And so, yes, it will hurt a lot.”

Many farmers in Central Arizona, such as Thelander, have known for years that their Colorado River water supply will eventually be phased out.

As part of a 2004 settlement between the federal government and the Central Arizona Debt Issues Project, farmers in some central Arizona irrigation districts have agreed to relinquish their water rights in exchange for receiving water at a reduced cost. by the year 2030.

But because Lake Mead’s water levels are still near record lows and are expected to fall further, water supply could end years before farmers expected.

Many factors contribute to the dwindling supply of the Colorado River system.

First, experts say more water is being diverted from the river than is entering the system.

The Colorado River wraps around Horseshoe Bend near Page, Arizona. A study last year found that river flow had decreased by about 20% over the past century, mainly due to climate change.

“This is a math problem – Lake Mead typically releases 10.2 million acres of water a year, and 9 million acres flow into it,” said Brad Udall, a senior scientist for water and climate research at Colorado State University. . “At some point, you have to fix it because you have an annual deficit of 1.2 million hectares, or you will drain the reservoir.”

In addition, there is a historic drought and climate change that is undermining the supply of the river.

Much of the Colorado River Basin has been gripped over the past two decades by what some scientists have called a mega-drought.

The period from 2000 to 2018 was the driest period of 19 years that the southwestern United States has experienced since the 1500s, according to an analysis of tree ring data published in the journal Science in 2020. The scientists also found that the human climate crisis was caused. can be blamed for almost half the severity of the drought.
Another study by U.S. Geological Survey scientists published in 2020 found that the flow of the Colorado River has decreased by about 20% over the past century and that more than half of the decline can be attributed to the heating temperature in the bowl.

Most of the river’s flow comes from snow that falls high in the Rocky Mountains of Colorado and southern Wyoming, said Chris Milly, a research hydrologist at the U.S. Geological Survey and co-author of the study.

Warming temperatures lead to a decrease in snowfall and an earlier snowmelt. But as the snow melts earlier and leaves bare soil, more heat energy from the sun is absorbed by the exposed soil. The warmer soil leads to more evaporation, which means less runoff of melting snow ends up in the river, Milly said.

“Evaporation is how the stream area cools itself,” Milly said. “And so if you have more evaporation, you have less water left to get into the river.”

The current conditions also do not look promising for the kind of above-average runoff needed this year to refill the river’s main reservoirs.

After an exceptionally hot and dry 2020, the precipitation for many of the basins remained lower than normal.

Soil moisture levels in the region are also among the lowest recorded, according to Paul Miller, a hydrologist for service coordination at the Colorado Ocean Basin River Forecast Center of the National Oceanic and Atmospheric Administration (NOAA).

This means that much of the snowmelt runoff during the summer is likely to be absorbed by thirsty soil and plants before it can even reach the river, Miller said.

For Fleck, all this suggests that the reduced flow in recent years is probably not a deviation, but rather a look at the challenges of a warmer, drier climate.

“We are now seeing the model for what the future of using the Colorado River Basin water looks like, where scarcity is the norm and drought is not a special issue in the short term,” he said. “It’s the way of life we ​​are now reducing climate change that is reducing the flow in the river.”

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