Rotational fallowing urged to conserve water

In the face of climate change, shifting weather patterns that drive prolonged droughts and multiple uses of water, finding adequate amounts of fresh water is becoming a critical issue.

The rate at which people consume water in some regions surpasses the rate at which it can be naturally replenished leading to chronic water shortages.

The western United States is a huge region where water shortages have become severe, especially in the Colorado River basin. The critical shortage puts the environment and fish species at risk and limits the potential growth of towns and cities.

Research by scientists at the Northern Arizona University in collaboration with 12 universities worldwide studied what was driving water depletion and looked at options to reduce the water shortage.

Scientists found that irrigated crop production accounts for 86 percent of all water consumed in the western U.S. and of that, the largest portion goes to crops going for cattle feed, such as alfalfa and grass hay. This in-depth study not only looked at the supply and demand of water in the Colorado River basin but traced the use of that water from the field where hay is grown to the end user, the consumer.

“What we have done is track the water use using new data science technology,” said Benjamin Ruddell with the School of Informatics, Computing and Cyber Systems and director of the FEWSION project. “FEWSION means food, energy, water systems data fusion. Unlike other data sets, this one is spatially detailed. For instance, if you live in a specific city and consume a specific product like beef, we can tell you the supply chain, how much water was used and where that water was used in that supply chain. It’s a fundamentally new capability, the ability to tie a spatially detailed supply chain to your beef supply.”

They traced the cattle downstream in the supply chain from the fields through the feedlots, the dairies and the feed processing and packing systems all the way to the consumer. The water that went into this infrastructure became referred to as virtual water.

“The ground-breaking maps produced by FEWSION made it possible to link river depletion through the supply chain to irrigated alfalfa and hay and to beef and dairy production, then to urban consumers of beef and dairy in each city and county,” said Ruddell.

The degree to which irrigated cattle feed uses water from the Colorado River far exceeds all other uses. He said that the water used for cattle feed is nearly three times greater than all the water used for urban, industrial and electrical power purposes combined.

“If you add up everything cities are using, power plants are using, people are using, industry is using, depending on what river basin you are in, all of that is less than just the water used to grow cattle feed,” said Ruddell.

“Agriculture as a whole takes the vast majority of water use and just cattle feed is half of the total. It’s a gigantic demand. If we just went after that issue, it could make a huge impact on the overall water stress in the west. Conservation by cities, power plants, agriculture as a whole have a role but cattle feed, growing hay and alfalfa, is the single biggest water user. You can’t solve the water problem without looking at this.”

He said that they used a set of models that link water use including irrigation for cattle feed directly to the impact on endangered fish species and they could demonstrate that cattle feed irrigation was having a significant effect on water stress and the aquatic ecosystem.

According to the U.S. Department of Agriculture’s 2019 Overview for Arizona, 280,000 acres were planted in alfalfa with a yield of 8.3 tons (7.5 tonnes) per acre for an annual production of more than 2.3 million tons of alfalfa (two million tonnes). In addition, 325,000 acres were planted in hay and harvested with a yield of 7.72 tons per acre (seven tonnes per acre) for an annual hay production of 2.5 million tons (2.2 million tonnes). One field can get nine to 10 cuttings a year.

To solve the problem in the Colorado River basin, the authors of the research paper have suggested rotational fallowing of farmland. Compared to other crops, alfalfa and hay fields are very easy to fallow. Water can be shut off temporarily then turned back on later.

“But who is going to pay for that?” asked Ruddell. “How do we make this good for the farmer? People are not going to stop eating beef and milk. Large changes in diet could put farmers and ranchers out of business. What we need to be doing is creating systems where people who need more water pay farmers to use less water for feed. This system could work with a farmer upstream and a city located downstream in the river basin. Those downstream cities pay the farmer upstream to use less water to make sure that the water stays in the river for the city’s use.”

The system would be volunteer based. Ruddell said it should not be a regulatory or an environmental law situation.

“Farmers should welcome it,” he said. “It’s a way to protect their business, stay in business and protect their communities while doing their part to manage the western water crisis. The alternatives are much worse for everyone.”

Farming, being so weather dependent, can be high risk business. But Ruddell said that a fallowing system along the line they propose would provide a dependable fixed income. A value-added effect of the system is that the water remaining in the river benefits the environment and the aquatic ecosystem.

When asked what the food alternative for cattle would be in the event fields are fallowed, Ruddell said that corn is a viable and abundant cattle feed. According to USDA, in 2019 corn producers planted 91.7 million acres of corn and about a third of the annual corn crop is used for feeding cattle, pigs, and poultry.

“I can hardly believe that such a large fraction of our western water problems is linked to irrigation of cattle feed, or that such a large fraction of our water problems could be fixed with a single prescription like fallowing,” said Ruddell in the news release. “It’s rare that science finds a ‘silver bullet’ that solves such a big problem so well, and so affordably,”

The research paper was published in the journal Nature Sustainability.

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