Most of these people live in Asia and Africa, where long dry seasons make crop production difficult or impossible without irrigation. For them, conventional irrigation technologies are too expensive for their small plots, which typically encompass fewer than five acres. Even the least expensive motorized pumps that are made for tapping groundwater cost about $350, far out of reach for farmers earning barely that much in a year. Where affordable irrigation technologies have been made available, however, they have proved remarkably successful.

I traveled to Bangladesh in 1998 to see one of these successes firsthand. Torrential rains drench Bangladesh during the monsoon months, but the country receives very little precipitation the rest of the year. Many fields lie fallow during the dry season, even though groundwater lies less than 20 feet below the surface. Over the past 17 years a foot-operated device called a treadle pump has transformed much of this land into productive, year-round farms.

   
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