More than half of water from Colorado River used for agriculture industry, report finds

Researchers have quantified just how much water the agriculture industry in the Western U.S. is taking from the Colorado River, one of the most important river systems in the region.

More than half of the Colorado River's total annual water flow is being used to irrigate agricultural land, according to a paper published Thursday in Communications Earth & Environment.

Waters from the Colorado River have not reached its delta in the Gulf of California for more than 50 years because nearly every drop is being consumed as the waters flow south, Brian Richter, president of Sustainable Waters, a global water education service, senior freshwater fellow at the World Wildlife Fund, told ABC News.

The new report offers a detailed account of where all the water is going, in part to help aid the lower-basin states -- Arizona, Nevada and California -- in negotiations to conserve water allocated from the Colorado River, a deal brokered by the U.S. Bureau of Reclamation last year, said Richter, who authored the paper. The legal agreements surrounding the Colorado River's water are set to expire in 2026.

"There's some pretty intense negotiations taking place right now," Richter said.

Irrigation for agriculture was responsible for 74% of direct human usage and 52% of overall water consumption, the report found.

Irrigated farms are using three times more water than all of the cities and industries combined, according to the report. Two particular crops used for cattle feed -- alfalfa and grass haze -- accounted for one-third of all the Colorado River's water.

The Colorado River has about 19% less volume than in the year 2000 and is expected to drop to 30% by 2050 if temperatures continue to rise, scientists say. Lake Mead and Lake Powell -- the largest reservoirs in the country that provides water to 40 million people in the U.S. and Mexico -- have both dropped by 160 to 180 feet over the last two decades, Richter said,

The study is a comprehensive assessment of how the Colorado River's water is consumed. It examines both human usage and natural losses over the Colorado River's nearly 1,500-mile length. The researchers calculated the water budget of the Colorado River basin based on the average annual water use and water losses between 2000 and 2019.

While the Bureau of Reclamation keeps track of much of the water in the river system, there are big portions, such as the Gila River Basin in Arizona, that were not formally included in the Colorado River Compact of 1922, Richter said.

Mexico was found to use 7% of the overall Colorado River water supply, and the Gila River Basin was found to consume 9% of the total, according to the report.

"Right now, it's very difficult for people to plan when they don't really know how much water's going to be available -- even next year," he said.

There will need to be a significant reduction in water use to avoid future shortages, the authors cautioned. In addition, more water will need to be left in the river to support the diverse ecosystems along its full length, the paper found.

Farmers are facing the brunt of the cutbacks on water allocation, putting pressure on the industry to adapt to a future with less water. It is estimated that farmers must reduce their water use by 20% in the near future, Richter said.

"We know that we can't continue to grow the same crops that we've been growing for the last century in the American Southwest," Richter said.