New from the journal Nature

With chronic water shortages afflicting the Colorado River, discussions about how to cut usage have increasingly focused on a thirsty crop that consumes an especially large share of the river’s water: hay that is grown to feed cattle and produce beef and dairy products.

In a new study, researchers found that alfalfa and other cattle-feed crops consume 46% of the water that is diverted from the river, accounting for nearly two-thirds of agricultural water use. The research also shows that agriculture is the dominant user of Colorado River water, accounting for 74% of the water that is diverted — about three times the combined usage of all the cities that depend on the river.

The study presents the most detailed analysis of its kind to date, including extensive data on where the river’s water goes across seven Western states and northern Mexico. The research sheds new light on how the river’s water is used at a time when representatives of the federal government, states and tribes are seeking long-term solutions to reduce water use and adapt to climate change.

“It’s important to understand where all of the water goes,” said Brian Richter, a researcher who led the study. “This is the first complete and detailed accounting.”

Jack Schmidt, from the Center for Colorado River Studies and Future of the Colorado Project agrees.

"Without this kind of basic accounting, we can't make strong decisions about how water should be used in the future. This is where an acurate accounting begins."

The study, which involved a team of 12 researchers and was published in the journal Communications Earth & Environment, expands on previous research by including water use data for Mexico; the Gila River, a major tributary in Arizona; and supplies that are transported through canals and pipelines to areas outside the Colorado River Basin.