Consideration of Climate Variability and Change in Agricultural Water Resources Planning

Abstract

Although agriculture and its use of water resources are obviously sensitive to climatic conditions, past research has seldom identified the effects of climate variability and climate change on the fully developed relationship between crop yield and irrigation. There is potentially great value in understanding the role of climatic uncertainty on this relationship because of the dependence of agriculture on irrigation and the scale of water consumption for irrigation. Probability distributions of crop-water production functions (CWPF-PDs) are demonstrated as being useful encapsulations of the climate-yield-irrigation relationship for decisions at various levels of time and space. Combined with reliable climate teleconnections or climate forecasts, CWPF-PDs can be a central decision support tool for questions of risk and reliability. For long planning horizons, potential climate change predicted by multiple general circulation models (GCMs) can be assessed in the context of agricultural water resources. By analysis of changes in the CWPF-PDs, conclusions regarding the efficacy and sustainability of water resources and agricultural policies can be made. A semihypothetical case study for the Lake Victoria Basin in East Africa is used to illustrate these methodologies, and potential future climate impacts as predicted by the CGCM1, ECHAM3, and HadCM2 GCMs are discussed.