UCR experts examined the costs of hundreds of Colorado River water projects over 20 years
By David Danelski, UC Riverside
The most cost-effective way to conserve the dwindling waters of the Colorado River may not come from building new reservoirs, canals, or wells, but from changing how water is used on farms that consume most of it.
That’s the conclusion of a comprehensive study by UC Riverside’s School of Public Policy, conducted with the Utah Rivers Council.
Led by UCR graduate student Paloma Avila, the study examined 462 federally funded Colorado River conservation and supply projects, totaling about $1 billion (in 2023 constant dollars) between 2004 and 2024, using available spending data from the U.S. Bureau of Reclamation.
It found that agricultural conservation programs saved water as low as $69.89 per acre-foot, while new supply efforts—such as reservoirs, wells, and wastewater treatment facilities—cost more than $2,000 per acre-foot on average. In water conservation, an acre-foot is a measure of the amount of water required to cover one acre of land to a depth of one foot, or approximately 325,851 gallons.
“It’s important to understand where investments in conservation are being made across the Colorado River Basin and to evaluate their effectiveness,” Avila said.
The study has broad implications because the Colorado River is the economic lifeblood for agriculture in seven states while providing water for as many as 35 million people in and out of the basin.
The UCR analysis showed that the greatest savings occurred where most of the river’s water is used, said Mehdi Nemati, an assistant professor of public policy, co-author of the study, and Avila’s faculty advisor.
“Eighty percent of the water in the basin is consumed by agriculture,” Nemati said. “Agricultural conservation—particularly incentive programs—gives us the lowest cost with the highest savings.”
The vast scale of agricultural water use includes maintaining pasture grasses and alfalfa crops, grown for cattle feed, that cover wide stretches of Wyoming, Colorado, and Arizona. Keeping those fields green often means flooding entire parcels.
Nemati explained that paying ranchers and farmers to cut back on such practices, even temporarily, can deliver meaningful water savings at relatively low cost.
In California’s Palo Verde Valley and parts of Arizona, federal funds have been used to pay farmers to leave alfalfa fields unplanted for a season or two. Other programs encourage “deficit irrigation,” in which growers intentionally use less water while still harvesting a crop. Subsidies have also supported growing other crops and replacing flood irrigation with sprinkler or drip systems that deliver water with much greater precision.
The findings, Nemati said, are particularly useful for policymakers.
“If the goal is to prioritize limited funding, then projects with the highest cost effectiveness make the most sense—especially in agriculture,” he said.
Urban and suburban water utilities, particularly in Southern California, have already made substantial gains. Over the past 30 years, urban areas cut water use by about 40 percent despite population growth, Nemati noted.
“The low-hanging fruit in the urban sector is probably gone,” he said.
Cities reduced water consumption through native landscaping, drip irrigation, efficient fixtures, leak detection, and wastewater recycling. While more can be done, costly projects such as desalination plants would produce relatively small gains across the seven-state river basin.
The study also raises questions about how conserved water is used. Some expect it to stay in the river to benefit ecosystems, while others assume it will be redirected to growing cities. Nemati said this uncertainty complicates public perceptions of conservation.
“There is no defined water right for saved water, and that becomes a little bit challenging,” he said.
The study—“Public Spending and Water Scarcity: An Empirical Analysis of USBR Investments in the Colorado River Basin”—was published in the Journal of the American Water Resources Association. In addition to Avila and Nemati, its co-authors are Ariel Dinar[DD6] , a UCR distinguished professor emeritus of environmental economics and policy, Daniel Crespo, a UCR postdoctoral scholar, [MN7] [MN8] and Zachary Frankel and Nicholas Halberg of the Utah Rivers Council[DD9] .
Nemati believes the message for policymakers is clear: agricultural conservation is the cheapest path forward, and the biggest gains will come from the fields and pastures that dominate the basin’s water use.
“If we are concerned about the Colorado River’s water balance, household landscaping or toilets won’t help us much,” Nemati said. “That’s just a drop in the bucket compared to the shortages we face. Agriculture stands out as the most cost-effective—at least for now.”
Avila did research for the study while earning her master’s degree.
“I’m grateful to have been able to take the quantitative and policy analysis skills I gained in my Masters of Public Policy program and apply them directly to a pressing, real-world challenge,” she said.
