As the temperature rises, the atmosphere becomes thirstier. It draws up more moisture from woods, private gardens, and agriculture fields. Climate change, according to Bolinger, has led conditions on the ground in areas of the Colorado River basin to push up against the defined drought categories. The climate is just not capable of producing enough rain to make up for lost groundwater.
The amount of rainfall that falls over the river basin is the same as it was hundreds of years ago, but due to increased demand on this water, some people are going to need to be restricted in what they can do with it. For example, farmers who depend on the water for their crops will need to adjust their practices or risk losing their income. Climate change is making these problems worse by causing temperatures to rise, which leads to more demand being made on the system.
A study published in April 2014 by researchers at Stanford University found that the ongoing drought was likely caused by man-made climate change. It concluded that without additional carbon dioxide emissions, the level of water in the Colorado River would drop far below its present day level by the end of the next decade. The report also suggested that if current trends continue, the level of water in the river will be reduced by one third by 2100.
Climate change is also affecting the river's water supply. According to a research released in 2020 by US Geological Survey experts, the Colorado River's flow has decreased by around 20% over the previous century, with increased temperatures across the basin accounting for more than half of that reduction. This decrease will likely become even more severe in the future.
The survey's lead author, David Zoya, said: "If the climate changes as expected, then the flow reductions we calculated would be even greater than what we measured."
Furthermore, excessive use of the river by consumers in the American Southwest has put additional pressure on its flow. The vast majority of the river's water comes from snowpack and rain in the Rocky Mountains, but it also receives input from other sources such as glaciers and groundwater. In order to meet growing demand for irrigation and industry, some farmers and businesses have been taking advantage of subsidies offered by various governments to promote water conservation. However, these efforts have not stopped the depletion of the basin's resources.
Despite these problems, there are still places where one can enjoy the natural beauty of the Colorado River. It runs through four states (Colorado, New Mexico, Utah, and Arizona) before reaching Mexico's Gulf of California. Although parts of it are popular destinations for hiking and boating, others are better left undisturbed by people.
The Americans simply referred to it as "the huge drought." For many years, the United States has consumed more water from the Colorado River than it receives from melting mountain snow. The Colorado River is supplied by snowmelt from the Rocky Mountains, but precipitation is decreasing as a result of climate change. When there is not enough water flow to meet demand, areas of intensive use like agriculture suffer from scarce supplies of water.
The lack of snow and rain in the Western United States is called "water scarcity". Climate change is expected to increase water scarcity in this region. One study published in Nature in 2014 found that over half of the major U.S. rivers will experience increased flooding or drought intensity by the end of the century if climate change does not reduce precipitation significantly. Another study published in Science in 2016 concluded that most of the Western United States would face increasing drought risk by 2025 under current climate policies.
Even when there is enough water to go around, people can still have too much of it. The Colorado River has suffered because of overuse of its waters for irrigation and household use. In fact, some studies say that if present trends continue, the river will be completely dry in 15 years.
Water shortages have become a serious problem in the United States. Some states like California depend on the Colorado River for their drinking water, so losing access to it can lead to public health emergencies.
In the previous 20 years, the Colorado River basin has undergone three D4 droughts, including the present one. The basin's most severe drought seasons have occurred in 2002, 2018, and 2021. "The droughts that we're witnessing are becoming more severe because of the temperature component; they're warmer," said Bolinger. "And so we're starting to see some long-term trends where the climate is changing and what that means for the water supply."
The current drought is the third in just over a decade. It began in late 2010 with heavy rainfalls that filled up reservoirs across the desert Southwest. But the spring floods of 2011 were the highest ever recorded in Southern California. Then, during the following summer, drought struck virtually all of the region's major river systems. By January 2012, only 7% of normal levels remained in Lake Mead, the reservoir behind the Hoover Dam.
How does climate change affect the Colorado River? Drought is just one factor that can lead to lower-than-normal flows from the river. Climate change can also impact runoff by affecting the amount of precipitation that falls as rain vs. snow. If it's warmer, there's less chance of snowfall, which is important because many rivers such as the Colorado depend on snowmelt to fill their reservoirs. As sea levels rise, low-lying areas of the river's delta may become inundated and unable to soak up rainfall like they used to.
During one of the driest 22-year periods in history, the Colorado River's flow has decreased. According to scientists, the West is undergoing a megadrought, which is being exacerbated by humanity's heating of the globe. The Colorado River basin has been particularly heavily struck by the drought during the last year. Since late summer 2015, most areas of the basin have experienced severe shortages of water.
The river itself is still flowing at record levels, but its watershed is experiencing unprecedented dryness. The lack of rain is causing the groundwater table to drop, putting more pressure on remaining reserves.
Scientists say there is no indication that the flow rate will increase any time soon. They also point out that if conditions in the basin continue to get worse, they may need to restrict how much water people can use for agriculture and industry.
A study published in August found that if the current pace of climate change continues, most of the Colorado River's major tributaries will be unable to supply enough water to meet future needs. It predicted that by as early as 2045, most of the river's annual runoff could be consumed by humans.
The study was conducted by researchers from the University of Arizona and Stanford University. It concluded that if current trends in consumption and climate change continue, some areas of the Southwest might not receive any precipitation between October and March.