The spatial and temporal impacts of climate change on irrigation water requirements and yield for sugarcane grown in Swaziland have been assessed, by combining the outputs from a general circulation model (HadCM3), a sugarcane crop 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 water requirements (IRnet) and yield (t ha-1) using a reference site and selected emissions scenario (SRES A2 and B2) for the 2050s (including CO2-fertilisation effects). The simulated baseline yields were validated against field data from 1980-1997. An aridity index was defined and used to correlate agroclimate variability against irrigation need to estimate the baseline and future irrigation water demand (volumetric). To produce a unit weight of sucrose equivalent to current optimum levels of production, future irrigation needs were predicted to increase by 20-22%. With CO2-fertilisation, the impacts of climate change are offset by higher crop yields, such that IRnet is predicted to increase by 9%. The study showed that with climate change, the current peak capacity of existing irrigation schemes could fail to meet the predicted increases in irrigation demand in nearly 50% of years assuming unconstrained water availability
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