The 53-city International Water Management Institute survey showed 80 percent of those cities regularly use untreated or partially treated waste water for urban agriculture. Officials said the practice is often critical to farmers’ incomes and urban food security but raises health concerns. “Irrigating with wastewater isn’t a rare practice limited to a few of the poorest countries,” said IWMI researcher Liqa Raschid-Sally, lead author of a report on the survey. “It’s a widespread phenomenon, occurring on (49 million acres) across the developing world …”
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Source: http://www.upi.com/Science_News/2008/08/21/Untreat
Population pressure and increasing water competition in a changing climate require us to take stock of the availability and use of water across scales. Water availability not only influences farmers’ commercial prospects but also irrigation-related enterprises and agri-businesses. Greater water scarcity could jeopardize irrigation and agricultural markets while excessive water use can lead to declining ecosystems, water quality and soil health. IWMI advises development partners and the public and private sectors on all aspects of water resource availability and use through a variety of advanced modeling and remote-sensing products and tools, including 
The ability of farmers to engage in or expand irrigation depends on the prevailing socioeconomic, ecological and political contexts, which are often complex, non-linear and changeable. Overcoming systemic barriers to farmer-led irrigation development while taking advantage of existing opportunities 
A lack of affordable credit, particularly for women and resource-poor farmers, is one of the main barriers to expanding farmer-led irrigation in low- and middle-income countries. But 
Scaling farmer-led irrigation requires strengthening human capacity and knowledge exchange among all actors and stakeholders involved. IWMI takes an action research approach, working with national and international research institutions, governments, extension agents and public and private organizations to co-develop the scaling ecosystem and strengthen capacity to drive scaling networks and collective action. We support the