Hydrological Response of a Semiarid Olive Orchard Microcatchment Under Theoretical Climate Change Scenarios

The increase in aridity and torrential events in semiarid areas predicted by the Intergovernmental Panel on Climate Change is expected to significantly affect their hydrological response and thus their associated nonpoint source pollution and erosive dynamics. This study quantifies rainfall-runoff patterns in a 6.1-ha olive orchard microcatchment in Southern Spain, representative of a marginal farm, to determine the impact of extreme events under different theoretical climate change scenarios. To this end, the physically based distributed hydrological model WiMMed (Watershed Integrated Management in Mediterranean Environments) was implemented, calibrated, and validated with experimental data throughout the study period (2005-2012). The root mean square error values for hourly runoff and flows derived from calibration and validation were approximately 1 and 0.3 mm s(-1), respectively. An increase in mean temperatures of between 1.6 degrees C and 3.9 degrees C, a decrease in rainfall of between 13.7% and 26.6%, and larger torrential events were simulated in this study following possible climate change scenarios. The results revealed the nonlinear and complex interactions of the different processes conditioning the water balance due to opposite tendencies of rainfall decrease and the increase in temperature and rainfall intensity. The most significant change was found in the scenario that simulated an increase in the torrential character of the events. A mean runoff coefficient of over 0.6 was obtained in the catchment, which should be considered in future aspects of water management.