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Geology professor Karl (Walt) Flessa ’68 recently appeared on News Hour with Jim Lehrer to discuss his research on the drop in the level of the Colorado River since the 1930s. A professor in the department of geosciences at University of Arizona in Tucson, Flessa has spent the past ten years of his career attempting to discover how this drastic reduction of freshwater flow has affected the Colorado River Delta in Mexico’s northern Gulf of California. “We want to answer the question, ‘What happens when you turn off a river?’” he explains.
In the mid 1930s, the need for irrigation and the building of Hoover Dam began to divert the river’s water for American use. Major dams enable diversion of approximately 90 percent of the river for cities and crops. Mexico is entitled to 10 percent of the river’s annual flow as governed by international treaty. As a result, in most years, the Colorado River no longer reaches the sea.
Because no observations of the delta’s fauna were recorded before the advent of the dam, Flessa and his students try to reconstruct what the fauna and habitats of the river delta were like by studying clam shells. By using techniques such as carbon dating and stable isotope analysis, they are able to determine the abundance of such species and map out the area’s ecosystem in what he jokingly refers to as the “Predambrian” (before the dams) period.
“What we’ve found is that turning off the river has decreased the productivity in the Gulf of California — the salinity is up, the nutrient supply is turned off. It has completely changed the ecosystem,” says Flessa.
Through his research, Flessa has found that at least one species of the area, the Colorado Delta Clam (Mulinia coloradoensis), is at risk of extinction due to the change in river flow and increased salinity in the delta. This species was also a major food source for other fauna; the change in river flow thus also decreased the abundance of predatory birds and fish. There is also the possibility that the absence of vital nutrients have affected the fisheries of the Gulf of California.
Flessa’s research has also uncovered data that can be used by government agencies and private groups on both sides of the border to restore and preserve the natural habitats of the area.
“Lafayette got me involved in research very early and that’s where I think the real value of my education is,” says Flessa, a geology graduate.
Flessa’s work has been featured in Science magazine, The Washington Post, and Dallas Morning News. He earned his Ph.D. from Brown University in 1973, and was a Humboldt Scholar in Germany. His work has been funded by the National Science Foundation, the U.S. Geological Survey, and Environmental Defense. He recently received a fellowship from the Udall Center for Public Policy to examine the status of natural ecosystems in the scheme of water allocation, allowing him the opportunity to further explore the idea that nature has a right to keep and utilize its own resources.