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Boosting food yields with water harvesting

The integrated use of multiple water-harvesting techniques can improve food security in the face of climate change in rain-fed farming landscapes

Marrakesh, 15 November 2016

Judicious combinations of high-performing water-harvesting techniques can increase yields in rain-fed farming areas and provide farmers with an important buffer against climate change, according to an assessment released today by FAO of 42 water-harvesting practices in Burkina Faso, Morocco and Uganda. The assessment has been released ahead of the launch later this week at the UN conference on climate change of a global FAO-led initiative to address water scarcity in agriculture.

 Water harvesting encompasses a wide range of techniques, such as the collection of road runoff, the construction of “valley tanks”, contour bunds and “half-moons”, and the use of composting and mulching. Such techniques are used in all three case-study countries, but not always in combination. The FAO report “Strengthening agricultural water efficiency and productivity on the African and global level” used a multi-criteria analysis to evaluate the biophysical, technical and socio-economic performance of a range of water-harvesting approaches. The aim was to determine those combinations that would show the largest environmental, socio-economic and productivity benefits under differing circumstances.
“All the techniques we examined can be useful on their own but their impact on the overall water balance is more substantial if they are combined systematically at the landscape scale,” said FAO officer Maher Salman, the lead author of the report.

Water harvesting has a range of microclimatic benefits,” said Salman. “The primary effect is to increase water retention and hence soil moisture. This helps even out temperature peaks and lows, and it also increases the ability of soil bacteria to fix nitrogen, which means higher-fertility soils.”

 Water harvesting also helps control water runoff and avoid excessive soil erosion, thereby reducing the loss of nutrient-rich sediments from farming systems.

According to the report, more coordination, planning and management is needed at the landscape scale to take advantage of the synergistic effect of integrating water-harvesting techniques.

“It is relatively straight-forward to determine the best combinations of techniques in a given landscape,” said Salman. “But deploying them at the landscape scale requires agencies, farmers and other stakeholders to cooperate, work together, and share the costs and benefits.”

More also needed to be done to  adopt water-harvesting techniques – not only in Burkina Faso, Morocco and Uganda but in other countries worldwide facing water scarcity.

“If we can provide farmers with needed support to ensure that that water harvesting will boost their productivity and thus increase their income, they will quickly adopt, innovate and adapt techniques to their specific needs,” said Salman. “Uptake would be quickest and most widespread, he said, if supported by secure land rights, greater access to markets (for both input and produce), and farmer-to-farmer and other learning approaches.

 Improving water retention is increasingly important in the face of climate change,” said Eduardo Mansur, Director of FAO’s Land and Water Division. “Water scarcity is one of the leading challenges of the twenty-first century,” he said. “Climate change poses a major threat to agriculture, especially in drylands, and action is needed now. This report provides a useful way ahead for millions of farmers in rain-fed systems.”

Another plank in FAO’s platform to help farmers adapt to climate change, “Coping with water scarcity in agriculture: a global framework for action in a changing climate”, will also be launched on 15 November.

“The aim of the framework is to build a global partnership across sectors and among all stakeholders, because only a concerted, cooperative effort will be effective in providing food security in the face of increasing water scarcity,” said Mansur.