A Hydrological Modeling of a Semi-Arid Andarax River Basin In Southern Spain

The 2,265 km2 Andarax river basin is located in Southern Spain. The basin is strongly affected by tectonic activity and coincides with one of the existing depressions in the Betic Cordilleras. The lithology is mostly Triassic schists and limestone in upland areas and Neogene-Quaternary sandstones, conglomerates and loams of marine origin in medium and lower-lying areas. The terrain changes from sea level at the coast to more than 2,500 m in the Sierra Nevada Mountains. It is one of the most arid regions in Europe with a precipitation of 200-350 mm/year, which mainly falls (70%) in autumn and winter. In the mountainous areas, where the unit Triassic schists dominates nearly all precipitation is converted into overland flow which runs directly to the river. When the river reaches the medium and lower-lying areas most of the water infiltrates into the highly permeable Detritic aquifer. Only at rare occasions and for high rainfall events the river discharges into the Mediterranean Sea and consequently nearly all excess rainfall generated from the upstream catchments areas is discharged as groundwater flow which thus determines the water availability in the delta region. The rather unique hydrological behavior of the Andarax river basin is simulated by the MIKE SHE code, which is a physically based, distributed and integrated hydrological model. Particular emphasis is given to the simulation of the seasonal and spatial distribution of recharge within the river catchment. As the availability of traditional hydrological data for the Andarax river basin data is rather sparse remote sensing data will be used to improve the estimation of the spatial and temporal distribution of the evapotranspiration. For this purpose an energy based model included as an option in the MIKE SHE code will be used based on remote sensing data for leaf area index (LAI), global radiation, albedo and air temperature.