The spatial and temporal impacts of climate change on irrigation waterrequirements and yield for sugarcane grown in Swaziland have been assessed, bycombining the outputs from a general circulation model (HadCM3), a sugarcanecrop growth model and a GIS. The CANEGRO model (embedded with the DSSAT program)was used to simulate the baseline and future cane net annual irrigation waterrequirements (IRnet) and yield (t ha-1) using a reference site and selectedemissions scenario (SRES A2 and B2) for the 2050s (including CO2-fertilisationeffects). The simulated baseline yields were validated against field data from1980-1997. An aridity index was defined and used to correlate agroclimatevariability against irrigation need to estimate the baseline and futureirrigation water demand (volumetric). To produce a unit weight of sucroseequivalent to current optimum levels of production, future irrigation needs werepredicted to increase by 20-22%. With CO2-fertilisation, the impacts of climatechange are offset by higher crop yields, such that IRnet is predicted toincrease by 9%. The study showed that with climate change, the current peakcapacity of existing irrigation schemes could fail to meet the predictedincreases in irrigation demand in nearly 50% of years assuming unconstrainedwater availability.
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