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°C and 3.9°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.

Time-lapse ground-penetrating radar (GPR) surveys, combined with automated infiltration experiments, provide a non-invasive approach for investigating the distribution of infiltrated water within the soil medium and creating three-dimensional images of the wetting bulb. This study developed and validated an experimental protocol aimed at quantifying and visualizing water distribution fluxes in layered soils under both unsaturated and saturated conditions. The 3D images of the wetting bulb significantly enhanced the interpretation of infiltration data, enabling a detailed analysis of water movement through the layered system. We used the infiltrometer data and the Beerkan Estimation of Soil Transfer parameters (BEST) method to determine soil capacitive indicators and evaluate the physical quality of the upper soil layer. The field survey involved conducting time-lapse GPR surveys alongside infiltration experiments between GPR repetitions. These experiments included both tension and ponding tests, designed to sequentially activate the soil matrix and the full pore network. The results showed that the soil under study exhibited significant soil aeration and macroporosity (represented by AC and p_MAC), while indicators related to microporosity (such as PAWC and RFC) were notably low. The RFC value of 0.55 m³ m⁻³ indicated the soil’s limited capacity to retain water relative to its total pore volume. The PAWC value of 0.10 m³ m⁻³ indicated a scarcity of micropores ranging from 0.2 to 30 μm in diameter, which typically hold water accessible to plant roots within the total porosity. The saturated soil hydraulic conductivity, K_s, values ranged from 192.2 to 1031.0 mm h⁻¹, with a mean of 424.4 mm h⁻¹, which was 7.9 times higher than the corresponding unsaturated hydraulic conductivity measured at a pressure head of h = −30 mm (K₋₃₀). The results indicated that the upper soil layer supports root proliferation and effectively drains excess water to the underlying limestone layer. However, this layer has limited capacity to store and supply water to plant roots and acts as a restrictive barrier, promoting non-uniform downward water movement, as revealed by the 3D GPR images. The observed difference in hydraulic conductivity between the two layers suggests that surface ponding and overland flow are generated through a saturation excess mechanism. Water percolating through the soil can accumulate above the limestone layer, creating a shallow perched water table. During extreme rainfall events, this water table may rise, leading to the complete saturation of the soil profile.