A New Mexico State University scientist's new economic analysis of the cost to keep the Rio Grande flowing for the endangered silvery minnow found that Albuquerque residents and some central New Mexico agricultural users do suffer, while other water users downstream benefit.

The net gain for New Mexico agriculture would be $68,000 a year, with central New Mexico losing $68,000 a year and southern New Mexico adding $217,000, primarily because of the high-value crops grown in the region, said Frank Ward, an agricultural economist at NMSU.

Farther down river, El Paso area farmers would get a boost of $203,000 a year, and El Paso municipal water users would gain $1.27 million annually.

The big beneficiaries to maintaining the upstream habitat for the minnow include El Paso industrial and municipal water users, who would gain more than $1 million a year during drought years, he said. The study was to be published in the April issue of Journal of the American Water Resources Association.

“Protecting instream flows for the silvery minnow produces positive market economic benefits for agriculture and water users for the upper Rio Grande Basin,” said Ward, who conducted a 44-year mathematical simulation of future water inflows.

The upper Rio Grande Basin covers an area from southern Colorado to Fort Quitman, Texas.

The study was funded by a $700,000 grant from U.S. Geologic Survey, with support from the NMSU Agricultural Experiment Station and the water research institutes of New Mexico, Colorado and Texas.

In recent years, the federal government, under the auspices of the U.S. Endangered Species Act, has decreed that the Middle Rio Grande must be kept flowing for the endangered silvery minnow. That year-round minimum minnow flow rate has been determined by biologists to be 50 cubic feet per second in the 60-mile San Acacia stretch of river north of Socorro.

This reach of the upper Rio Grande is where most of the silvery minnows are found in the wild.

In wet years, it's not a problem, but under drought conditions keeping the river flowing puts a strain on already drought-stressed water supplies, with farmers along the Middle Rio Grande being forced to give up irrigation water to keep water in the river for the minnow.

“What we found wasn't all that unexpected,” Ward said. “To get more water in the 60-mile San Acacia reach of the river, you have to have reduced diversions from other water users.

“Those two water users would be farmers in the Middle Rio Grande Conservancy District and the city of Albuquerque.”

The Albuquerque metropolitan area is developing surface water treatment facilities for future use, which was anticipated in the NMSU computer model. James Booker, an economics professor at Siena College in Loudonville, N.Y., directed the mathematical modeling for the economic analysis.

“More water for the minnow means agriculture in central New Mexico would suffer,” Ward said. “They're going to have to take water out of production, and their acreages might fall and the growing season might be shortened.”

The unexpected result of the study wasn't that the Middle Rio Grande would lose, but that farmers in the Elephant Butte Irrigation District in southern New Mexico would gain, he said. Still, considering the overall size of the region's high-octane agricultural output, that income boost is only about a 1 percent increase.

But by far the biggest beneficiary of rise in river minor flow would be El Paso municipal and industrial users, who rely heavily on surface water.

“About 40 percent of their water comes right out of the river,” Ward said. “El Paso water users would gain in greater water quantities and reduced need for groundwater, which is a more expensive source.”

The original data for the current endangered species economic review came from a series of drought studies that began in 1996, he said. Three universities — NMSU, Colorado State University and Texas A&M University — began examining water flows from the Colorado Basin to the upper Rio Grande Basin, which ends just south of El Paso.

The study, which compiled economic and hydrology data, evaluated two legal documents, the Rio Grande Compact of 1938 and the 1905 U.S. Mexico Water Treaty, in handling water shortages.

The resulting mathematical model keeps track of economic losses caused by drought in the three states. The scientific model was shelved in 2001 after it was published, but shortly thereafter political and environmental interest began to turn toward endangered species, specifically the silvery minnow in New Mexico.

The silvery minnow, once one of the most abundant fish in the Rio Grande Basin, now inhabits only a fraction of its former range. About 157 miles of the Rio Grande and a tributary through central New Mexico are now critical habitat for the endangered Rio Grande silvery minnow.