June 20, 2007—Agronomist Esteban Jobbagy takes a water sample from the Rio Mendoza River in Argentina in April 2007.

Snowmelt from the Andes mountains that straddle the Argentina-Chile border flows into the river through a series of foothills, where grapes for an expanding Argentine wine industry are grown.

The water ends in the Monte Desert, where indigenous peoples called the Huarpes have lived for centuries.

Vineyard owners are diverting increasing amounts of water from a network of channels and streams originally crafted for irrigation centuries ago by several indigenous groups.

Jobbagy works at Argentina's National University of San Luis. He is trying to prove scientifically what some agronomists have begun to suspect—that rapid development between the Andes and the desert is putting pressure on the desert's aquifer, or underground water supply.

"People [here in the desert] live in a system that is harsh yet so far has survived because of one thing, and that's groundwater," Jobbagy said.

"We are in an area where you can walk for days without seeing surface water, yet the aquifer is a source of life."

• More Photos in the News
• Today's 15 Most Read Stories
• Free Email Newsletter: Focus on Photography