COLOMBO, SRI LANKA (5th July 2017) – The use of untreated wastewater from cities to irrigate crops downstream is 50 percent more widespread than previously thought, according to a new study published this week in the journal Environmental Research Letters.
The study relies on advanced modeling methods to provide the first truly comprehensive estimate of the global extent to which farmers use urban wastewater on irrigated cropland. Researchers analyzed data with geographic information systems (GIS) rather than depending on case study results, as in previous studies.
The researchers also assessed for the first time ‘indirect reuse’, which occurs when wastewater gets diluted but still remains a dominant component of surface water flows. Such situations account for the majority of agricultural water reuse worldwide, but have been difficult to quantify on a global level due to different views of what constitutes diluted wastewater versus polluted water.
Considering consumer safety the foremost priority, study authors highlight the need to mitigate public health risks through measures taken along the entire food supply chain. This includes improved wastewater treatment, but also preventive steps on farms and in food handling, since capacity for water treatment is increasing only slowly in developing countries.
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 theÂ
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