M. López-Chicano

Conditioning factors in flooding of karstic poljes—the case of the Zafarraya polje (South Spain)

Abstract The Zafarraya polje undergoes periodical flooding, of which the last episode (1996–1997) was analysed in detail on this paper. On the basis of the retention curves of the two lakes that formed in the northwestern and southwestern sectors, we calculated the total infiltration capacity of the polje to have a maximum value of 3–3.5 m3/s and so we infer that when the flow of the Arroyo de la Madre exceeds this figure, there will be a risk of flooding in the polje. We also propose a model for the 1996 flood that can be extended to other similar occurrences in this and other poljes where we can establish the role played by groundwater and surface water during this flood. In response to the heavy precipitation, the flow of the Arroyo de la Madre rose abruptly, exceeding the infiltration capacity of the main swallow holes on the polje, causing first the northern lake and then the southern lake to form with only surface water supply. The water table of the karst aquifer rose sharply, reaching a situation of equilibrium between the level in the lakes and the water table in this sector of the karst aquifer that prevented infiltration through the swallow holes. In the case of the southern lake, there were even cases of swallow holes that began to operate as estavelles. During this phase of maximum flooding, one single lake was present, which was divided into two once more when the water table of the karst aquifer in the polje sector began to fall and surface supply also began to decrease.

Kinematics of faults between Subbetic Units during the Miocene (central sector of the Betic Cordillera)

The kinematic analysis of the low-angle faults that separate the major units of the Subbetic Zone indicates two main stages of translations. In the first stage, of Burdigalian to basal Tortonian age, the hanging walls moved toward the WSW, and thrusts developed in some sectors of the External Zones. Simultaneously, in the Internal Zones, the activity of extensional detachments shows the same kinematics. In the second stage, affecting up to basal Tortonian rocks, northwest-verging thrusts were active. The Subbetic tectonic units probably underwent relative rotation during the development of these structures.

Gypsum karst in the Betic Cordillera (south Spain)

Among the numerous karstified gypsum outcrops of the Betic Cordillera, in this article we present three extreme examples, with markedly different origins and development: (1) the Antequera gypsum karst, where diapiric phenomena have had a decisive influence on the geomorphological and hydrogeological evolution of the area; (2) the karst in gypsum of Vallada, with its processes of hyperkarstification of gypsum caused by the presence of significant quantities of halite; and (3) the Sorbas gypsum karst, where a complex speleogenetic development is demonstrated by a succession of vadose and phreatic passages within a multilayer aquifer. In these three cases, we have considered the geomorphological evolution of gypsum karst based on hydrogeological information gathered in each of the outcrop areas in a way which integrates both aspects into a more generalized speleogenetic model.

The role of western Mediterranea tectonic evolution in the geometry of a karstic domain in the Betic Cordilleras (Sierra Gorda, Spain): importance of a tardy extensional regime

AbstractLocated in the central part of the Betic Cordilleras, the large carbonate Sierra Gorda Massif provides an example of a west-Mediterranean karstic aquifer. In spite of a complex polyphased tectonic history, the fracturing presents, from aerial views and at outcrop scale a quite organised geometry. Four fracture directions are found over the massif. N000—010, NOS0-070, N090–100 and N140–170. The statistical and geostatistical approach allows the characteristics (lengths, orientations) and the spatial structure for each fracture set to be determined. The N000–010 and N140–170 sets are grouped in packets whereas the two other sets are grouped in bands. The microtectonic study describes the evolution of the massif in the geodynamic context of this part of Mediterranea, distin guishing three recent stages of brittle tectonic activity in t e massif: a WNW-ESE Middle Miocene compression, then a NNW-SSE to NW-SE compression with a poorly wrenching regime, and finally a probably pre-Quaternary N-S radial di...

The Effects of Non-TIDAL Components, Depth of Measurement and the Use of Peak Delays in the Application of Tidal Response Methods

The efficacy and applicability of tidal response methods (TRMs) were assessed in terms of the techniques used, the, data used in the analysis, and the implementation of the methods under different conditions. The tidal efficiency (TE) and time lag (TL) methods were applied to directly measured groundwater head (GWH) values in the Motril-Salobreña coastal aquifer and compared with the same pre-filtered time series after eliminating the non-tidal signals through the continuous wavelet transform (CWT) procedure. The use of maximum and minimum groundwater peaks and sea-level peaks in combination to obtain different delay values and the effects of asymmetries in tidal fluctuations were assessed. Application of the TE method yields different D values when a complete groundwater head time series is considered, instead of the net induced tidal oscillation. Moreover, when the asymmetry of tidal oscillations is not taken into account, the application of TL may yield a higher uncertainty. In unconfined coastal aquifers, hydraulic diffusivity can be overestimated by the TE method if the non-tidal components are not removed from the measured time series of groundwater head. However, prior filtering provides better diffusivity results when the TE method is applied. The depth of the water head measurements leads to different D values when applying the TE method as a consequence of the changes in the specific storage with depth, which result from changes in pressure. The results of the application of the TL method depend on whether maximum or minimum peaks are used. Since the use of maximum peak delays can overestimate D, minimum peak delays are recommended, as they yield D values that are closer to the values obtained using the TE method.

Numerical Modeling of Groundwater Age Distribution in Motril-Salobreña Coastal Aquifer (SE Spain)

A mass and age transport numerical model of Motril-Salobrena coastal aquifer has been developed considering a new age dating survey with environmental tracers (3H–3He, 85Kr, and 39Ar). The method applied for the simulation of age transport was the direct age, which enables the direct simulation of the age defined as a transport specie. The model includes also variable density since saltwater encroaches from the sea boundary. The results of the model reproduce the saline wedge and the age distribution explaining the hydrodynamic processes in the discharge zone of the aquifer. The model describes the aquifer hydrogeological processes complementing the uncertainties of groundwater age dating, as well as the integration of other hydrogeological information from previous studies. The calibration based on the age dating yields a better fit of the advective-dispersive parameters than the common approaches using groundwater levels or concentrations and could be applied to other aquifers. This information will allow a better management of the water resources against the changes due to anthropogenic activity and climate change.

Spectral Analysis of Time Series of Carbonate Aquifer of Sierra Gorda

Both Moon and Sun induce Earth tides. Signatures of the Earth’s crustal tides could be recorded in the groundwater in the form of rise and fall of its piezometric surface. In relationship with this phenomenon, there is a scarcity of these kinds of studies in carbonate aquifers. Spectral analysis has been applied in Sierra Gorda aquifer located in the southern of Spain in order to determine the presence and statistical significance of cycles from different time data series like air temperature, barometric pressure, electrical conductivity, pH and piezometric level located in the north border of the aquifer. Diver and Hidrolab sensors to collect data every 1 and 6 h were installed in some of these springs and piezometric borehole. The piezometric data series have more than 25,000 hourly data. The period studied start in November 2010 and end in September 2013. In this site, it has been observed some spectral peaks that could be linked with crustal tides related to cyclic movement of Moon and Sun around Earth. The most significant peaks in piezometric levels that could be related to Moon and Sun show values of 12 h, 1 day, 14 days and 28 days. On the other hand, similar signal is recorded by pH and conductivity temporal data. The influence of Earth tides on pH and conductivity is less studied and would be necessary new investigations on this aquifer to confirm this possibility. The spectral signature of temperature and barometric data is quite different to others variables studied.

ISOTOPIC AND HYDROCHEMISTRY SPATIAL VARIATION OF SULFATE FOR GROUNDWATER CHARACTERIZATION IN KARSTIC AQUIFERS

The Sierra Gorda aquifer is one of the most extensive of southern Spain. The main groundwater discharge is produced at its northern boundary through several high-flow springs. In this study, stable isotopes of dissolved sulfate (δ34S and δ18O) and groundwater chemistry were used to determine the origin of the sulfate and to characterize the groundwater flow. We sampled the main springs, as well as other minor outlets related to perched water tables, in order to determine the different sources of SO42- (e.g. dissolution of evaporites, atmospheric deposition, etc.). The substantial difference in the amount of dissolved SO42- between the springs located in its northwestern part (≈25 mg/l) and those elsewhere in the northern part (≈60 mg/l) suggests zones with separate groundwater flow systems. A third group of springs, far from the northeastern boundary of the permeable outcrops, shows higher SO42- content than the rest (≈125 mg/l). The isotopic range of sulfate (-0.3 to 14.82‰ V-CTD) points to several sources, including dissolution of Triassic or Miocene evaporites, atmospheric deposition, and decomposition of organic material in the soil. Among these, the dissolution of Triassic gypsum —which overlies the saturated zone as a consequence of the folds and faults that deform the aquifer— is the main source of SO42- (range from 12.79 to 14.82‰ V-CTD). This range is typical for Triassic gypsum. The higher karstification in the western sector, together with important differences in the saturated thickness between the western and eastern sectors, would also be due to the tectonic structure and could explain the difference in SO42- contents in the water. This singular arrangement may cause a higher residence time of groundwater in the eastern sector; thus, a higher contact time with Triassic evaporitic rocks is inferred. Accordingly, the stable isotopes of SO42- are found to be a valuable tool for identifying areas with different flow systems in the saturated zone of karstic aquifers, as well as for evaluating aspects such as the degree of karstification.

MORPHOMETRIC ANALYSIS OF KARST DEPRESSIONS ON A MEDITERRANEAN KARST MASSIF

Abstract Dolines are the most typical landform in karst landscapes. They play an important role in karst hydrogeology; they are effective sediment traps that provide information about past climates and karst evolution, and can also be indicators of tectonic activity. The morphometic analysis of those depressions can help in their study and interpretation. However, detailed identification and delineation of dolines becomes increasingly difficult when the study area is very large, of limited access or covered by vegetation. Here, we have used a method developed by the authors for automatic identification and delineation of karst depressions based on the use of a pit removal algorithm. Next a complete morphometric analysis of the karst depressions has been carried out. The main advantage of the methodology is that by delineating and identifying the depth of each doline from its rim, many morphometric statistics can be obtained, including the relation of doline depth and area with respect to altitude, the main doline orientations, doline density, the fractal dimension of doline area and frequency, and point field analysis, among others. The results are interpreted from a geomorphological point of view and the mapped dolines can be easily integrated into geomorphological mapping. A case study is presented from the large Sierra Gorda karst massif in southern Spain, where 3100 depressions have been identified. A strong structural control of doline shape and orientation is demonstrated; the main areas of doline density are highlighted and doline size is shown to follow a fractal law.