Hidden cost of Colorado River diversions is $2.4 billion annually


This stretch of floodplain near Yuma, Ariz., is a small remnant of what remains of the original floodplain vegetation along the Colorado River.
Photo credit: Karl W. Flessa.

Full size photo is available from source.

Society is losing $2.4 billion per year because the Colorado River's water no longer flows all the way to the Gulf of California, says a University of Arizona researcher.

It's the first dollar estimate of the benefits society would get from the natural functioning of a healthy Colorado River delta.

Functioning ecosystems provide benefits, known as ecosystem services, to humans. However, so much Colorado River water has been dammed or diverted for human uses that the river's delta no longer works the way it used to.

"The day-to-day functioning of ecosystems provides benefits," said Karl W. Flessa, a professor in UA's department of geosciences. "What I've done is estimate what's the value to society if you just leave the water in the river. Human populations are losing that value when the water is diverted for other purposes."

When Colorado River water is diverted for human uses such as agriculture or drinking water, there's a hidden cost to society, Flessa said.

Flessa's calculation reflects the loss of benefits the river originally provided, including natural flood control, natural wastewater treatment and providing nursery areas for fish and other marine organisms.

Flessa will present his research at the Gulf of California conference held June 13-16 at the Westward Look Resort in Tucson, Ariz. His presentation, "$200 per acre-foot: Nature's services and the natural value of water in the Colorado delta and estuary," will be given at 2:20 p.m. on Monday, June 14, in the Colorado River Delta session.

His research was supported by the National Science Foundation, Environmental Defense and a fellowship from UA's Institute for the Study of Planet Earth and UA's Udall Center for Studies in Public Policy.

Flessa argues that the price water users pay should reflect the cost to society.

"The price we pay for Colorado River water should include the cost of lost ecosystem services," Flessa said. "Included in the price of water should be mitigation costs for the environmental consequences of diverting water."

The additional amount users should pay for the water could be used for ecosystem restoration in the delta, he said.

"It's a crass, philistine thing to do, but we can put a dollar value on the impact. After all, our common currency is currency."

Flessa suggests that an environmental impact, or mitigation fee, should be included in the price of water. The money from mitigation fees could be used for ecosystem restoration in the Delta. He said one way to use the money would be to purchase farmland and let it go fallow. Another way would be a forbearance agreement in which the farmer is paid not to grow crops. In either case, water that would have irrigated that land could then remain in the river and flow to the delta.

The major water diversions on the Colorado began with Hoover Dam in the 1930s. Before that time, the Colorado River delta was primarily three ecosystem types: desert, floodplain and estuary. What were floodplain and desert have now been almost 100 percent converted into cropland. The delta's once-biologically rich estuary has been transformed into ocean shelf.

Other researchers have calculated the monetary value of services provided to society by various ecosystems, including natural floodplains, natural estuaries, deserts, ocean shelf and croplands.

Flessa applied those figures to the land area of the Colorado River delta to get the dollar value of ecosystem services provided by the region before all the dams and water diversions. He then figured out what ecosystem services are provided by the current land use types in the delta region. The difference between the two figures is the benefit lost to society: 6 cents per 100 gallons of water diverted, or $2.4 billion annually.

Flessa said, "It's a question of evaluating the environmental impact of diverting the river's water," he said. "I want to emphasis that this is not a matter of the value of water to fish or plants -- this is a matter of the value of water to humans."

Converting floodplains to croplands and estuary to ocean shelf means a loss of ecosystem services.

"The original ecosystem services provided are worth more than the ecosystem services we now get from the transformed landscapes," he said.

He cautions that his analysis is limited to the environmental impacts of the changes. "I don't want to say this is a net loss. We have the cities like Phoenix and Tucson. We also have the market value of the crops raised."

Flessa said, "I'm arguing that everybody should pay more for their water. I'm not happy about having to pay more -- but I know it will do some good. You'll get some restored habitats and a restoration of some of those ecosystem services."

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