"Drip Irrigation May Not Be Efficient, Analysis Finds"

From The New York Times
By HENRY FOUNTAIN
Published: November 17, 2008 

In an effort to make irrigation more efficient — to obtain more “crop per drop” — farmers have adopted alternatives to flooding and other conventional methods. Among these is drip irrigation, shown above, in which water flows only to the roots. Drip systems are costly, but they save much water.

Or do they? A hydrologic and economic analysis of the Upper Rio Grande basin in the Southwest, published in The Proceedings of the National Academy of Sciences, suggests that subsidies and other policies that encourage conservation methods like drip irrigation can actually increase water consumption. 

“The take-home message is that you’d better take a pretty careful look at drip irrigation before you spend a bunch of money on subsidizing it,” said Frank A. Ward, a resource economist at New Mexico State University and author of the study with Manuel Pulido-Velázquez of the Polytechnic University of Valencia in Spain.

With flood irrigation, much of the water is not used by the plants and seeps back to the source, an aquifer or a river. Drip irrigation draws less water, but almost all of it is taken up by the plants, so very little is returned. “Those aquifers are not going to get recharged,” Dr. Ward said.

Drip irrigation also generally increases crop yields, which encourages farmers to expand acreage and request the right to take even more water, thus depleting even more of it. “The indirect effect is very possibly to undermine policy attempts to reduce water consumption,” Dr. Ward said.

Policymakers, he added, must balance the need for more food and for farmers to make a living with water needs. “It’s fair to say that subsidies are very good for food security and very good for farmer income,” Dr. Ward said. “But they may be taking water away from other people.”