MEXICO CITY — Eliminating water waste and mismanagement on farms -- rather than building dams or diverting rivers -- would go far toward alleviating the world's water crisis, officials and activists gathered at an international forum here said.

Farming accounts for 70 percent of the water consumed and a majority of its waste, said representatives of some of the 130 nations attending on Saturday the 4th World Water Forum to discuss water management around the globe.

Mismanagement of resources leads to a lack of safe drinking water for one-fifth of the world's population, the United Nations said in a report.

In the developing world, the water crisis is almost totally defined in relation to agriculture, with constant images of drought-blasted fields, withered corn stalks and skinny cattle.

With 525 million small farms in the world, farmers suffer the most from each problem discussed at the forum: poverty, disease, and the lack of sanitation and clean water.

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

With 2.5 billion people living off the land, change is a daunting task.

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

Traditionally, governments have responded to the problems of small-scale farmers -- defined as those with plots of 2 hectares (5 acres) or less -- by building big dam projects.

But McCully says most small farms are so high up in the hills or removed from rivers that they can't benefit from them.

Meanwhile, irrigation systems urgently need attention, according to 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.

Participants in this forum have pledged to focus on the world's poor, many of whom live on less than 2 1/2 gallons of water per day -- one-thirtieth of the daily usage in some 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. Added to these woes are 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 U.S.-Mexico relations.

In 2004, farmers in Texas were outraged when Mexico failed to let flow 1.3 million acre-feet of water into a border river under the terms of a 1944 treaty. An acre-foot is enough water to flood an acre (0.4 hectares) of land under 12 inches (30.5 centimeters) of water.

The long-standing Rio Grande water debt was paid in full by Mexico in 2005 after heavy rains replenished reservoirs.

Agriculture cannot be ignored in the water equation, according to Gerald Galloway, a civil engineering professor 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."

Source: Associated Press