Assessing the potential of rainwater harvesting as an adaptation strategy to climate change in Africa

Stabilizing smallholder crop yields under changing climatic conditions in Africa will require adequate adaptation strategies focused on soil and water management. In some regions, rainwater harvesting (RWH) is used already to decrease the susceptibility of crops to frequent dry spells. Findings from this thesis show that Africa is likely to see significant changes in rainfall patterns during crop growing seasons, including higher intensity rainfall and more frequent very long dry spells. It is shown that RWH is a valuable adaptation strategy to climate change in Africa for maize, millet, and sorghum for a number of reasons. RWH could bridge ~30% of the yield gaps attributable to water deficits in the 2050s, thereby reducing future irrigation requirements. However, yield increases from improved water availability remain marginal (e.g. ~5-6% for millet and sorghum), unless combined with improved fertility measures (doubling of yields possible). Key benefits, potentially of greater importance than increased water availability from RWH, include protecting seeds, concentrating nutrients, and reducing long-term soil degradation. While RWH strategies show great biophysical potential as adaptation strategies, there remain a number of locally specific barriers to their adoption which need to be addressed to ensure their successful implementation at larger scales. As humans normally respond to perceived risks brought on by certain situations, it was hypothesized that climate change perceptions may be key in pro-moting the adoption of adaptation strategies such as RWH at the field level. In Burkina Faso, farmers had skewed perceptions of climate change (e.g. perceived decrease in precipitation when there are observed and projected increases), and thought of RWH as a central adaptation strategy despite not addressing projected impacts directly. Widespread RWH adoption across three field sites (Burkina Faso, Ethiopia, and Tunisia) rather depended heavily on government and NGO intervention. Overall, RWH could be an integral part of “adaptation packages” aimed at smallholder farmers, but should not be promoted as an independent solution to climate change in rainfed Africa.