MEXICO CITY (By Mark Stevenson, Associated Press) March 19, 2006 — Farms and their wasteful irrigation systems are a major contributor to water scarcity on the globe, nations at a world water summit said Saturday.

Farming accounts for 70 percent of the water consumed and most of its wasteful use, said representatives of 130 nations at the World Water Forum discussing water management.

One-fifth of the world's population lacks safe drinking water, the United Nations said in a report last week that laid much of the blame on mismanagement of resources.

"Farmers are central to the whole picture. They use the majority of the world's water, and farmers are where most of the world's poverty is concentrated," Patrick McCully, director of International River Network, a non-governmental organization, said at the forum.

Agriculture cannot be ignored in the water equation, said Gerald Galloway, a civil engineer and visiting scholar with the U.S. Army Corps of Engineers.

"It is an important part of the U.S. economy, and it's even more important in the developing world," he said. "You have to be able to provide water for agriculture."

With 525 million small farms in the world — and 2.5 billion people living off the land — farmers suffer the most from the problems discussed at the forum: poverty, disease, and the lack of sanitation and clean water.

Drought-parched fields, withered corn stalks and skinny cattle make up the face of the crisis in the developing world.

Getting farmers to use water less extensively is daunting, speakers said.

"There are great problems with irrigation. We must persuade our farmers to go to less extensive crops," said Michel Rocard, former prime minister of France. "It's a question of changing the whole agricultural method."

Traditionally governments have responded to the problems of small farmers — defined as those with plots of 5 acres or less — with big dam projects.

But most small farms are so high up in the hills or removed from rivers that they cannot benefit from them, said McCully.

The answer is more efficient irrigation systems, said Ute Collier, of the World Wildlife Fund.

"We can't afford to waste water in irrigation systems that are 30 to 40 percent efficient," he said. "If we could get that part of the equation done, we could probably cut down the number of dams we're building by half, at least."

Greater efficiency would free up money to help provide clean drinking water and food to small farmers who, despite raising food, constitute most of the 842 million people in the world who go hungry.

Many of the world's poor live on less than 2 1/2 gallons of water per day — one-thirtieth of the daily usage in developed nations.

Collier's work has focused on improving irrigation for notoriously thirsty cash crops, like cotton and sugarcane, although they are seldom grown on the smallest farms.

Agriculture based on fields that temporarily flood is also a major problem because most of that water is wasted through evaporation, the forum was told.

Other problems include pesticide and herbicide runoff from farm fields that pollute rivers and lakes, as well as soil erosion and salt buildup from irrigation.

In Mexico, host of the international forum, farm water disputes are the among the most sensitive issues in its relations with the United States.

In 2004, farmers in Texas were outraged when Mexico failed to let billions of gallons of water flow into a border river under a 1944 treaty.

Texans also accused Mexico of growing alfalfa — a water-hungry feed crop — in desert areas. One state politician suggested that the United States retaliate by reducing its flow into another border river, the Colorado.

Mexico went to court last year to stop the United States from lining one of its irrigation canals with concrete. Mexico claims its farmers had become dependent on water seeping out of the earthen canal, located near the two countries' border. The case has not been resolved.

Europe also has its conflicts. Spain would like France to share some of its water, but Rocard, France's former prime minister, said the French are reluctant to do so until the Spaniards improve their water management.