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Irrigation is widely promoted as a powerful tool to combat hunger and malnutrition, boosting agricultural output, food security, and rural livelihoods. But a new by the United Nations University Institute for Water, Environment and Health (UNU-INWEH) reveals a troubling paradox: irrigation expansion is most strongly associated with improved child nutrition in areas where water resources are already under severe stress.

The analysis, based on data from more than 70,000 households across 26 low- and middle-income countries, shows that expanding irrigation correlates with higher dietary diversity among children under five, a key proxy for micronutrient sufficiency and long-term health. Yet nearly one-third of irrigation gains occurred in regions that had already exceeded their renewable freshwater supplies before expansion began.

"While irrigation contributes to better child diets, these gains are often coming from areas that are already overusing water," said Dr. Marc F. Müller, lead author of the Policy Brief and Associate Research Professor of Water Security and Conflicts at UNU-INWEH. "This trade-off raises concerns about the long-term sustainability of irrigation-led development strategies."

The results, published alongside an in Nature Sustainability, call for context-sensitive, nutrition-oriented irrigation planning that explicitly weighs local water constraints and distributional outcomes.

"Our study questions the assumption that expanding irrigation will automatically translate to improved well-being in targeted areas," said Dr. Kyle Davis, the Food Security Module Lead of the UNU Sustainability Nexus Analytics, Informatics, and Data (AID) Program who led the analysis.

"In locations where governments and development agencies are investing in irrigation, mechanisms should be in place to ensure that the projects produce benefits to the food security and livelihoods of local communities."

By overlaying high-resolution irrigation maps with georeferenced household dietary data, the authors found that irrigation is often linked to nutritional improvements in water-stressed zones, where farming systems tend to focus on subsistence and staple food crops. In contrast, in water-rich regions, irrigation is more frequently used for commercially valuable export crops, such as coffee, soybeans, and palm oil, with limited nutritional spillovers to local communities.

"These findings challenge the assumption that irrigation automatically delivers inclusive, sustainable development," said Prof. Kaveh Madani, Director of UNU-INWEH. "We must rethink how, where, and for whom irrigation is deployed to ensure that gains in agricultural productivity translate into tangible nutritional, economic and environmental benefits."

According to the analysis, two-thirds of children in the surveyed communities still fall below the minimum dietary diversity threshold set by the FAO. Despite irrigation's potential, these figures underscore the scale of unmet nutritional needs and the risks of misaligned agricultural investments.

The two publications highlight the urgent need for more integrated approaches that bridge water, food, and health systems. Without such integration, irrigation may improve diets in the short term while undermining the very water resources essential for long-term food security and resilience.

Key findings include:

• The study analyzed georeferenced household survey data from over 70,000 rural households across Africa, Asia, Latin America, and the Middle East.
• Roughly 66% of children in the dataset fall below the FAO's minimum recommended dietary diversity threshold.
• Regions where irrigation expanded between 2000 and 2015 showed statistically significant improvements in child diet diversity.
• 36% of these irrigation gains occurred in water-stressed regions, where water use already exceeded renewable availability.
• In water-abundant areas, irrigation tends to favor export-oriented cash crops, which provide limited dietary benefits to local populations.

Policy recommendations include:

• Assess water stress before expanding irrigation, to avoid intensifying scarcity.
• Promote nutrient-rich, locally consumed crops rather than export-bound commodities.
• Ensure inclusive planning that defines and includes intended beneficiaries—especially women, children, and marginalized communities.
• Use child nutrition metrics, such as dietary diversity and stunting rates, to evaluate irrigation impacts.
• Align irrigation strategies with Sustainable Development Goals, particularly SDG 2 (Zero Hunger), SDG 6 (Clean Water and Sanitation), and SDG 1 (No Poverty).