This IWMI publication presents an assessment of the social impact of treadle pump technology for manual irrigation in eastern India, the Nepal Terai, and Bangladesh, South Asia’s so-called “poverty square.” This region, where 500 million of the world,s poorest people live, is underlain by one of the world’s best groundwater resources. Treadle pump technology can be a powerful tool for poverty reduction in this region. It “self-selects” the poor and puts to productive use the region’s vast surplus family labour. It is claimed that, on average, the treadle pump could raise the annual net household income by US$100. This report reviews evidence from a variety of studies, designed to test these claims.