Impact of Climate Change on Mediterranean Irrigation Demand: Historical Dynamics of Climate and Future Projections

Global warming is causing important changes in climate conditions, which must be studied in detail and locally in those zones where irrigated agriculture is developed-the major consumer of water worldwide. This study proposes the climatic characterization of a historical series (1971-2000) and its future projections (2011-2099) for an Irrigation District located in the Middle Ebro Valley (Spain), for three different scenarios: low, medium, and high global emission levels of greenhouse gases. Analysis of historical series reveals a significant increase in reference evapotranspiration (3.3 mm/year(2); 2.4 aEuro degrees) along with a decrease in precipitation (2.5 mm/year(2); 5.6 aEuro degrees). A comparison was carried out between real historical data and the scenarios produced by the climate models and it was observed that the most adequate climate model to predict climate in the study zone is MPI-ECHAM5. For the XXI century, MPI-ECHAM5 predicts cyclic climate trends but with a general increment in aridity, which intensifies according to the scenario chosen. Changes in climate are affecting agriculture doubly, since evapotranspiration requirements increase at the same time that water resources decrease. These effects are felt especially in irrigated agriculture, since the growing cycles of the main crops coincide with the months most affected by climate change.