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Assessing water resources in high mountain semi-arid zones is essential to be able to manage and plan the use of these resources downstream where they are used. However, it is not easy to manage an unknown resource, a situation that is common in the vast majority of high mountain hydrological basins. In the present work, the discharge flow in an ungauged basin is estimated using the hydrological parameters of an HBV (Hydrologiska Byråns Vattenbalansavdelning) model calibrated in a “neighboring gauged basin”. The results of the hydrological simulation obtained in terms of average annual discharge are validated using the VI-ETo model. This model relates a simple hydrological balance to the discharge of the basin with the evaporation of the vegetal cover of the soil, and this to the SAVI index, which is obtained remotely by means of satellite images. The results of the modeling for both basins underscore the role of the underground discharge in the total discharge of the hydrological system. This is the result of the deglaciation process suffered by the high mountain areas of the Mediterranean arc. This process increases the infiltration capacity of the terrain, the recharge and therefore the discharge of the aquifers that make up the glacial and periglacial sediments that remain exposed on the surface as witnesses of what was the last glaciation. [ABSTRACT FROM AUTHOR]

Abstract: The suitability of the combined microgravity and electrical tomography to detect and characterize caves deeply buried in limestones is tested. We have selected the buried Algaidilla cave, in the Estepa range (western Betic Cordillera), which is partially submerged below the water table and which was intersected between 26 and 66m in depth by two boreholes. At that location, microgravity, electrical resistivity tomography (ERT) and induced polarization (IP) data was collected along four profiles. Algaidilla cave is associated with a −0.5mGal residual gravity anomaly minimum. Microgravity models reveal an approximately horizontal N–S elongated shape with a maximum length of 150m and a width of 40m. Resistivity variations provide information on the cave sectors remaining above, as well as below the water table. Forward modeling and depth of investigation (DOI) support the suitability of ERT to constrain the cave geometry. The cave is identified as having an intermediate to low-resistivity feature, which approximately matches the 250Ω·m contour line along its ceiling. In addition, induced polarization models show high chargeability anomalies probably associated with decalcification clays. The location and approximately geometry of Algaidilla cave estimated from geophysical modeling suggests that nearby overburden may develop cave-ins and collapse sinkholes. Microgravity is proved as a powerful tool to detect caves at this depth, but this method alone fails to estimate the geometry. ERT results delineate the cavity both above and below the water table. Although the deepest sectors of the models should be interpreted with caution since they are less constrained by the data, below the water table the cavity shows great resistivity contrast with regard to the background carbonate. In addition, this study points out the usefulness of the IP method for detecting decalcification clays, often present at the base of karstic caves. [Copyright &y& Elsevier]

Abstract: We present a new set of brittle microtectonic measurements carried out in the Pliocene and Quaternary rocks outcropping in several key sectors of the western Betic and Rif orogen, the so-called Gibraltar orogenic arc. This data set, along with available earthquake focal mechanisms and borehole breakouts, allowed us to compile the Pliocene and Quaternary stress map of this area. This map provides new constraints for tectonic models and the present-day tectonic activity of the proposed active eastward subduction of oceanic lithosphere beneath the Gibraltar Arc and roll-back. The horizontal maximum compressive stress (S Hmax) is NW-SE in the Betic Orogen and N-S/NNW-SSE in the southern Rif Cordillera. There is a significant consistency between S Hmax and the displacement field deduced from GPS measurements with respect to the African plate: both appear to reflect the NW-SE convergence between the African and the European plates that is perturbed in the Rif. We propose that part of the eastern Rif behaves as a quasi-rigid block welded to the stable African plate. This block is bounded by important faults that localized most of the deformation disturbing the stress and surface displacement field. Pliocene to Quaternary N-S to NW-SE Africa-Europe plate convergence seem to be associated to the reorganization of the remnant Early Miocene subduction system in a continental–continental collision framework. Three-dimensional reconstruction of available seismic tomography plotted against the intermediate seismicity shows that only part of the old subduction system, whose orientation ranges from N20°E to N100°E, remains active: the portion ranging from N30°E to N40°E, orthogonal to the regional convergence. [Copyright &y& Elsevier]

Abstract: Seismic hazard is associated with recent and present fault activity in mountain ranges. In the Betic-Rif alpine mountain chain, tectonic activity started in the Cretaceous, and topographic uplift continues since Tortonian times as a consequence of the NW–SE oblique convergence between Africa and Eurasia. The deformation is active and produces seismicity that sometimes has catastrophic consequences. The Al Hoceima earthquake (February 24, 2004), considered one of the largest earthquakes ever recorded instrumentally in the westernmost Mediterranean (M =6.3), caused great damage in the region. Seismological studies agree that the main shock was situated on land, at the limit between the External and Internal Zones of the Rif, at a depth of 10–14 km. The focal mechanism points to a strike-slip solution with a NW–SE oriented P axis, quite similar to those of the significant 1994 earthquake swarm located to the north. The epicenter aftershocks distribution would signal the presence of a N–S oriented sinistral fault, activated by the NW–SE regional compression associated to plate boundary convergence. In this setting, the seismogenic fault ruptures related to these seismic events are expected to have reached the Earth''s surface. However, detailed field work carried out 1 month after the earthquake does not evidence any N–S strike-slip coseismic fault in the epicentral area. The main observed effects were landslides, damages to constructions, and locally open cracks indicating an unexpected NW–SE extension. Scarce N–S faults are normal, the main ones being located several kilometers away from the epicentral area. To explain this apparent contradiction between geological and seismological observations, we propose a decoupled tectonic model with crustal detachments that separate a deep brittle crust from an upper crust undergoing uplift, and the development of large folds and normal faults. This geological setting, common to internal zones of cordilleras, may need to be taken into account in future paleoseismicity studies and in the assessment of seismic hazard. [Copyright &y& Elsevier]

The internal zones of the Betic Cordilleras show a present-day relief that is mainly controlled by kilometre-size, symmetrical or north-vergent folds which developed mostly since Middle Miocene times. The Sierra Nevada, Sierra Alhamilla, Sierra de Los Filabres, Sierra Tejeda and Sierra de Ga´dor, among others, are roughly E–W trending high mountain ranges, corresponding to antiforms where metamorphic rocks crop out. The surrounding depressions are located in synforms, where Neogene rocks are preserved from erosion. Field evidence shows that the growth of the folds is coeval with fault development, and that at least three of them, i.e. the Padul Fault, the Zafarraya Fault, and the Balanegra Fault, may be considered to be active seismogenetic structures. The Zafarraya Fault, in particular, is thought to be responsible for the 1884 Andalucı´a Earthquake. The fault is located at the northern limb of the Sierra Tejeda antiform, and could be interpreted as a collapse structure developed along the external arch of the uplifted fold. The Padul and Balanegra faults are located at the southeastern border of the Granada Basin and south of the Sierra de Ga´dor, respectively. They belong to a set of NW–SE oriented faults that are mainly normal in character and indicate NE–SW extension. The set up, since 1999, of a GPS network within and around the Granada Basin and the planed installation of a new network in the Sierra Tejeda, will give us new insights on the present-day deformation behaviour of both folds and faults in the area. [Copyright &y& Elsevier]

• A cequias de careo constitute the oldest managed aquifer recharge system of Europe. • In Middle Ages, Muslims derived meltwater and recharged it through uncoated channels. • The managed aquifer recharge technique helped ensure water availability downstream. • This case study illustrates a paradigm that should be used in future water crises. • This MAR technique may prove key for adaptation to climate change in Alpine regions. In Sierra Nevada (southern Spain), the highest mountain range in southern Europe, the application of an ancestral Integrated Water Resources Management system (IWRM), based on the conjunctive use of groundwater and surface water, provides water resources for irrigation and supply in the driest months of the year in this semiarid mountain region. Meltwater is derived from the headwaters of the mountain streams and rivers through a set of uncoated channels excavated in the ground (locally known as acequias de careo) to infiltrate at the upper part of the valleys. Water infiltrated along the acequias de careo slowly flows down the hillsides, through the weathered zone of the hard rock aquifer and the glacial and periglacial sediments. The recharge accomplished through this Managed Aquifer Recharge technique (MAR) activates numerous springs located halfway down the hillside and increases the base flow of the rivers. In this study, focused on a careo channel located on the southern slope of Sierra Nevada called Acequia de El Espino, different archaeological, sedimentological, geophysical and hydrogeological techniques are applied to determine the age and the efficiency of this ancestral example of a MAR and IWRM system. Results suggest that the acequias de careo may be the oldest MAR system in Europe, and that this MAR technique could be applied in other high mountain alpine watersheds to mitigate the effects of climate change. [ABSTRACT FROM AUTHOR]