Rainwater harvesting – trapping runoff water and channeling it to more productive use – can greatly improve food production as well as water productivity (‘more crop per drop’).
An IFAD-funded collaborative program in Eritrea used geographic information systems (GIS) to identify the best locations for water harvesting systems in the country’s Southern Zone (Zoba Debub).
GIS-enabled spatial analysis
The first task was to compile hard-to-find information on land cover, topography, soils and precipitation – the key factors that determine whether a site is suitable for water harvesting. Using GIS and data integration tools, this information was transformed into maps showing suitability for different kinds of water harvesting systems.
The study looked at two kinds of systems: micro-catchments, where the field is also the catchment area; and macro-catchments, where many fields share water trapped from a large catchment area.
Site suitability was assessed for six micro-catchment systems (contour ridges, semi-circular bunds, small pits, small run-off basins, run-off strips, and contour bench terraces) under three different land-use scenarios: range shrubs, field crops, and tree crops.
For macro-catchment systems, suitability for catchment and for farming were analyzed separately, followed by an assessment of the constraint imposed by distance between farm and catchment area.
The results indicate excellent potential for water harvesting schemes – 70% of Zoba Debub is suitable for at least one micro-catchment system.
Making water harvesting work for farmers
Eight watersheds were shortlisted for potential pilot projects. The selection was based on the GIS analysis as well as other criteria including population concentration, and availability of water, land, and agricultural data.
To begin with, pilot water harvesting systems will be built at two of the eight shortlisted sites: Tselema watershed in the north-west of Zoba Debub, and Hazemo watershed in the south-east.
Food production in Eritrea has dropped by 60% over the last decade, largely because of frequent droughts. The ICARDA maps could help plan a water harvesting program to reverse this trend.