Science & Technology



Where does all the Colorado River water go? A huge amount goes to grow cattle feed, new analysis shows.

Elise Schmelzer, The Denver Post on

Published in Science & Technology News

More Colorado River water is used to grow a single crop than for drinking water, business needs and industrial uses combined across the seven-state river basin that’s home to more than 40 million people, a new analysis has found.

Water used to grow alfalfa — which is used to feed cattle — makes up more than a quarter of all human usage of the Colorado River, according to the analysis published last week in the academic journal Communications Earth & Environment.

The analysts’ work is the most comprehensive accounting of where precious Colorado River water goes as it flows downstream and thins to a trickle before reaching the Gulf of California in Mexico. The estimates account for water exported outside the basin to cities like Denver, Santa Fe and Los Angeles, as well as water use in Mexico and on the Gila River, one of the largest tributaries to the Colorado. The analysis also accounts for water lost to evaporation from reservoirs and in the natural environment.

“We thought it was really important to provide this fuller, more comprehensive perspective on where the river goes and to bring nature into the conversation,” said Brian Richter, the lead author of the analysis and president of Sustainable Waters, a global organization focused on water scarcity challenges.

Knowing how we are using water is important for shaping effective policy on how to manage the shrinking river in the future, Richter said.

The analysis comes as the seven Colorado River states, the 30 tribal nations on the river and the U.S. Bureau of Reclamation craft new long-term rules that will dictate how shortages are managed when there is not enough water — which is most years.

“We felt some urgency to get this study done because of the negotiations going on, and we wanted to get the most accurate numbers in front of them,” said Richter, who has published several other analyses of Colorado River use.

Here’s what Richter and his team learned when examining how the river was used between 2000 and 2019.

How much are we using?

Nearly every year, people use more Colorado River water than snow and rain can replenish.

In 16 of the 21 years from 2000 to 2020, humans used more Colorado River water than was produced by the spring runoff, according to Richter’s analysis. The overuse drained water from the two major reservoirs on the river, Lake Mead and Lake Powell, which are now only one-third full.

On average, human use combined with evaporation took about 19.3 million acre-feet of water out of the river yearly between 2000 and 2019.

Evaporation sucks up a chunk of the river — and that amount is likely to grow as climate change fuels warmer temperatures and drier air. On average, evaporation from reservoirs, soils and plants takes 30% of available water from the river system.

Water evaporated from the surface of Colorado River reservoirs accounts for 11% of the river’s water loss. Another 19% is consumed through evaporation from soil surfaces and plant leaves in ecosystems along the river and its tributaries.

What are people using the river water for?

After evaporation is accounted for, a quarter of the water diverted for human use is consumed by municipal, commercial and industrial purposes. The remaining three-quarters of the water goes to agriculture.

Ricther and his team analyzed data from a variety of sources to create the estimates in their report. They used data from the Bureau of Reclamation, the Arizona Department of Water Resources, the U.S. Department of Agriculture and previously published studies on the Colorado River.

Agriculture has long been the dominant use of Colorado River water, Richter said.

The basin produces billions of dollars of agricultural products every year, including a majority of the country’s winter vegetables, according to the Arizona Farm Bureau.

What crops are we growing with that water?


Cattle feed, primarily.

Alfalfa and other hays consume 6.4 billion cubic meters of water a year — more than half the 12.4 billion cubic meters used annually for irrigated agriculture. The two crops outpace the 4.1 billion cubic meters used annually by cities, companies and industry.

Other major crops include cotton and wheat, though they make up a tiny fraction of water use.

In the Upper Basin, where Colorado is located, the divide is even sharper.

Ninety percent of water used in the basin’s irrigated agriculture goes to grow cow feed. The other major crops combined — corn, wheat, sugar beets, dry beans and oats — make up the remaining 10%.

Alfalfa and hay in the basin use an average 3.1 billion cubic meters of water a year — more than three times the 975 million cubic meters funneled to municipal, commercial and industrial uses. Alfalfa alone doubles those uses.

Farmers grow alfalfa because it can be mechanically harvested, reducing labor costs. It tolerates weather variability and can better survive drought conditions, the analysis states. It also helps balance nitrogen in soils and reduces the need for fertilizer.

Farmers grow what is in demand, Richter noted, and people want beef and dairy. The cattle sustained by the hay and alfalfa produce the cheese, butter, burgers and steaks consumed across the country.

“I don’t want the general public to respond to a study like this and start blaming people for using so much water,” he said. “To blame ranchers and farmers for growing so much alfalfa or other cattle feed crops is not what I want to see come of this.”

What’s next?

Almost everyone agrees: Residents of the Colorado River Basin need to reduce water consumption.

Researchers have estimated a reduction of up to 29% is needed across the basin to stabilize Lake Powell and Lake Mead. More reductions will likely be needed as climate change and aridification increase evaporation and shrink water flows.

How exactly to implement those reductions fairly is the nexus of the ongoing negotiations between states, tribes and the federal government.

Programs to pay farmers to stop irrigating some of their acreage — such as the System Conservation Pilot Program in the Upper Basin — will need to be part of the solution, Richter said. Other options include swapping alfalfa and hay for other crops.

“These transitions in irrigated farming and ranching are not going to be easy for rural communities in the West,” he said. “We’re going to have be really smart and creative about the policies and programs that can facilitate those transitions so that we’re not losing these communities.”

Urban areas have successfully reduced water usage, Ricter said, but more can be done.

“We’re all responsible for this,” he said. “We can all contribute to this.”


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