Soil moisture and hydrological processes dynamics under climate and land use changes in a semiarid experimental basin, Brazil

Water resources sustainability is an increasing concern, requiring accurate estimates of the hydrological processes involved. This study evaluates the impacts of climate change (CC) and land use (LU) in a river basin in the Brazilian semi-arid. Using the Soil & Water Assessment Tool (SWAT), calibration/ validation was carried out based on limited measurements for discharge and using complementary remote sensing information for evapotranspiration (ET), as well as experimental data for soil moisture (SM). The evapotranspiration data used for calibration were obtained from the MOD16A2 product, at sub-basin scale. Principal component analysis was used to evaluate the interaction between variables. To assess the impacts of CC e and LU two scenarios were investigated: S1 – LU map without insertion of Permanent Preservation Areas (PPA), and S2 – with insertion of PPA. The Regional Climate Models (RCM) Eta-MIROC5 and Eta-HADGEM-ES for the Representative Concentration Pathway (RCP) 4.5 and 8.5 scenarios were adopted. The SWAT model adequately represented evapotranspiration, with Nash-Sutcliffe coefficient (NS) of 0.67 for calibration, and 0.74 for validation. For wet periods, the SM simulated values were similar to the experimental measurements with a coefficient of determination (R²) of 0.68. Complementary information for evapotranspiration and soil moisture across sub-basins successfully allowed consistent spatially distributed hydrological variables to be simulated. The model performance for validation using ET data was higher (NS = 0.77) compared to previous streamflow-only calibration strategies for flow (NS = 0.42) and soil moisture (NS = 0.46). Under the CC scenarios, natural vegetation restoration would compensate reductions in water availability.