Farmers in Africa have the twin challenges of feeding a growing population and producing crops with limited water access in a changing climate. Water harvesting lets them make the most of surface water from rain and rivers, using low-tech, affordable techniques that can be adapted to changes in weather patterns.

The WAHARA project is centralising data about traditional and new methods of harvesting water for crops. By testing various techniques in different African climates, it is developing a system for farmers and policy-makers to choose water-harvesting methods that are suitable for local conditions.

Results from the project show that this approach makes crops more reliable and abundant, so farms are more sustainable. Many techniques also preserve topsoil – maintaining levels of soil nutrients that crops need to grow.

Project coordinator Rudi Hessel from the Netherlands’ Wageningen University says: “We use a broad definition of water harvesting. We are looking at collecting water, storing it and how crops receive it.”

To identify the most appropriate options, the nine-member project has developed a computer-based tool – the Quick Scan Tool – that suggests water-harvesting methods that might suit a region’s landscape. However, farmers retain the final say on which techniques they will use as they have the most detailed knowledge of their immediate landscape and of how their farms operate.

“We have achieved real involvement of stakeholders and greater awareness of techniques from across Africa,” says Hessel. “The techniques have been effective,” he adds. “Crop improvement – in quality and volume – is visible.”

The project has advanced international knowledge of water harvesting. Its data is now included in WOCAT – the World Overview of Conservation Approaches and Technologies – a global database of sustainable land management measures.

Choosing techniques

WAHARA based its research around four rural study sites, each representing a typical African climate – arid in Tunisia, semi-arid in Burkina Faso, seasonally humid in Ethiopia, and sub-humid in Zambia.

Researchers gathered information about water-harvesting techniques from academic publications and local farmers. Typical technologies included stone lines that catch rain as it flows down slopes, ploughing methods that trap rainwater in the soil and small pits that hold rain around crops.

The project team then made a list of potential options for each study site, which local farmers narrowed down through a series of meetings with project partners. “The lists included technologies from other parts of Africa, so there was some technology transfer,” says Hessel. Training and support were on offer from the team to familiarise farmers with new methods.

Results from these studies showed that water harvesting can more than double yields, says Hessel. And he is positive about the project’s potential to improve agriculture on a wider scale. Its African partners are sharing information from the project in their home countries, while African policy-makers could use the Quick Scan Tool in their water-harvesting planning.

Based on a database of characteristics such as rainfall and evaporation, ground slope, soil type and landscape, the tool suggests techniques for a specific location in an Excel-based version of the program, or provides maps of characteristics for wider regions in a GIS (Geographical Information Systems) version.

The tool has already been shared with the EU-funded AfroMaison project and is freely available to other interested parties. Hessel however cautions: “The available data is not always precise. So suggestions have to be reviewed by specialists on the ground.”

Results from the project’s research are still being integrated across the study sites using modelling. “Final models will be more complex than the Quick scan tool,” says Hessel. “They will cover tens to hundreds of square kilometres and assess techniques’ wider impacts.” Models will also predict impacts of climate change, population growth and proposed policies.

“The EU provided money to work on something we feel is important,” Hessel adds. Africa has almost 15% of the world’s population and only 9% of global fresh water, according to the United Nations. Harvesting more water promises better crops – and a better quality of life – for people across the continent.