Assessing water resources availability and crop performance under climate change in Kenya's Bura irrigation scheme using SWAT and AquaCrop

The current study focused on Tana River Basin in Kenya, home to the Bura irrigation scheme (BIS). The BIS faces water supply shortages during critical months of crop development. This study aimed to evaluate the available water resources and crop performance using the Soil and Water Assessment Tool (SWAT) and AquaCrop, respectively, under historical and future shared socioeconomic pathways (SSPs) at the BIS. SWAT estimated the total available flows (TAF) at the BIS intake, whereas AquaCrop estimated crop water requirements (CWR), yields, and water productivity (Wpet) of rice and maize at various carbon (IV) oxide (CO2) levels. The study suggested that the TAF will remain relatively low during the early critical crop development stages in the main cropping season, August-October. Maize yields remained steady over the two cropping seasons under both constant and elevated CO2 levels in the historical and future periods, as opposed to those of rice. Elevated CO2 levels led to diminishing CWR. Moreover, rice showed a stronger response to elevated CO2 than maize. As a result, maize which is less affected by variations in CO2 and temperatures and has less crop water requirements will be better suited than rice for cultivation in the BIS under climate change. To ensure a sustainable water supply in the scheme, the government should increase rainwater harvesting during periods of high TAF. Moreover, there should be a focus on introducing crops that are tolerant to water and temperature stresses and that can reap the most from the elevated CO2 levels.