Risk analysis and economic viability of water harvesting for supplemental irrigation in semi-arid Burkina Faso and Kenya

Food insecurity affects a large portion of the population in sub-Saharan Africa (SSA). To meet future food requirements current rainfed farming systems need to upgrade yield output. One way is to improve water and fertiliser management in crop production. But adaptation among farmers will depend on perceived risk reduction of harvest failure as well as economic benefit for the household. Here, we present risk analysis and economical benefit estimates of a water harvesting (WH) system for supplemental irrigation (SI). Focus of the analysis is on reducing investment risk to improve self-sufficiency in staple food production. The analysis is based on data from two on-farm experimental sites with SI for cereals in currently practised smallholder farming system in semi-arid Burkina Faso and Kenya, respectively. The WH system enables for both SI of staple crop (sorghum and maize) and a fully irrigated off-season cash crop (tomatoes). Different investment scenarios are presented in a matrix of four reservoir sealants combined with three labour opportunity costs. It is shown that the WH system is labour intensive but risk-reducing investment at the two locations. The current cultivation practices do not attain food self-sufficiency in farm households. WH with SI resulted in a net profit of 151-626 USD year−1 ha−1 for the Burkina case and 109-477 USD year−1 ha−1 for the Kenya case depending on labour opportunity cost, compared to −83 to 15 USD year−1 ha−1 for the Burkina case and 40-130 USD year−1 ha−1 for the Kenyan case for current farming practices. Opportunity cost represents 0-66% of the investment cost in an SI system depending on type of sealant. The most economical strategy under local labour conditions was obtained using thin plastic sheeting as reservoir sealant. This resulted in a net profit of 390 and 73 USD year−1 ha−1 for the Burkina Faso and Kenyan respective site after household consumption was deducted. The analysis suggests a strong mutual dependence between investment in WH for SI and input of fertiliser. The WH system is only economically viable if combined with improved soil fertility management, but the investment in fertiliser inputs may only be viable in the long term when combined with SI.