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
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Contact: Karl W. Flessa
kflessa@geo.arizona.edu
520-621-7336
University of Arizona
10-Jun-2004