Rainwater harvesting can be an important strategy to increase crop yield sustainably, especially in marginal areas of the world. In a study published in Global Environmental Change, researchers identify areas of the world where water harvesting still has an untapped potential. Photo: L. Piemontese

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RAINWATER HARVESTING

East Africa and Southeast Asia are hotspots for water harvesting

Untapped potential means water harvesting can increase crop production up to 60–100 per cent in Uganda, Burundi, Tanzania and India

Story highlights

• Rainwater harvesting can be an important strategy to increase crop yield sustainably, especially in marginal areas of the world

• Researchers identify 167 examples of successful water harvesting across the world

• All cases helped define six “archetypes” crucial for successful water harvesting

LET IT RAIN: Without rain, no agriculture. Improving the collection and storage of the precious liquid is not sufficient to ensure sustainable food production, but it can certainly help.

Rainwater harvesting can be an important strategy to increase crop yield sustainably, especially in marginal areas of the world.

That in turn, can improve human wellbeing.

In a study published in Global Environmental Change, centre researchers Luigi Piemontese and Ingo Fetzer, together with colleagues from Italy, Switzerland and Sweden, identify areas of the world where water harvesting still has an untapped potential.

Their work is an attempt to create a wider, global estimate of the potential of water harvesting.

The results can complement conventional biophysical analysis on the potential of these practices.

Our assessment can serve as a methodological blueprint for identifying even more potential water harvesting implementations in the world.

Luigi Piemontese, lead author

Six “archetypes”

Based on information from the World Overview of Conservation Approaches and Technologies (WOCAT) database, Piemontese and his colleagues managed to identify 167 examples of successful water harvesting across the world.

What they had in common was that they helped define six “archetypes” crucial for successful water harvesting.

The guiding methodological question was: Where in the world can we find the same social-ecological conditions as in the 167 case studies?

  1. Smallholder farms in dense rural areas”
  2. “Remote farms in tropical developing areas”
  3. “Smallholder farms in arid developing areas”
  4. “Larger farms in remote arid areas”
  5. “Larger farms in high developed areas”
  6. “Slope farms in higher developed areas”

The archetypes cover large portions of Africa, Central America and Asia, and minor representations in South America and Eastern Europe.

Specifically, the adoption of water harvesting can increase crop production up to 60–100% in Uganda, Burundi, Tanzania and India.

Global map of archetypes of successful water harvesting, and regional snapshots in (b) East Africa and (c) South-Eastern Asia. When multiple overlapping archetypes, the archetype with the smallest spatial extent is shown. Click on illustration to access scientific study.

A conservative estimate

Altogether, these archetypes cover 19% of the global cropland area, but Piemontese and his colleagues warn that might be a conservative estimate.

Since the WOCAT database was originally developed to inform the design of development projects funded by international financial mechanisms of the Multilateral Environmental Agreements (e.g. the GEF, GCF and the Adaptation Fund), it does not include water harvesting cases in Northern America, Western Europe and Australia.

Based on that, there is more work to be done and this study may spur more investigations into parts of the world not covered by the WOCAT database.

Concludes Piemontese: “Our assessment can serve as a methodological blueprint for identifying even more potential water harvesting implementations in the world.”

Methodology

To out-scale the impact of the water harvesting case studies on crop production to the global scale, the researchers used a mixed methodology building on hierarchical clustering and spatial analysis. They selected and processed the social-ecological datasets to obtain spatially-explicit social-ecological indicators with a global coverage.

To identify the social-ecological similarity between water harvesting case studies with a cluster analysis, they used eleven global raster datasets of different social-ecological factors that are relevant to water harvesting implementation and success.

All the case studies used for the out-scaling process were taken from the WOCAT database.

Link to publication

Citation

Piemontese, L., Castelli, G., Fetzer, I., Barron, J., Liniger, H. et.al. 2020. Estimating the global potential of water harvesting from successful case studies. Global Environmental Change
Volume 63, July 2020, 102121

Link to publication

Luigi Piemontese's research focuses on freshwater consumption calculation in the framework of the Planetary Boundaries.

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