Francisco Sánchez-Martos

Identification of the origin of salinization in groundwater using minor ions (Lower Andarax, Southeast Spain).

The study of salinization of groundwater in the Detrital Aquifer of the Lower Andarax is highly complex due to the semiarid climate, the presence of evaporites, proximity to the sea and localized geothermal manifestations in the area. The salinization has been characterized by jointly studying the content of various minor ions (B, Br and Li) and a series of ionic relationships (B/Li, SO4/Cl, Na/Cl, Cl/B). The combined analysis of B and Li enabled the areas with a marked marine influence to be distinguished from those with an evaporite or geothermal influence. Lithium is directly related to water temperature whilst B content increases in more saline areas, since it is associated with the presence of evaporitic and/or marine influences. Bromine analysis enabled the identification of the principal processes that determine the salinity of the water along the coastal zone: the presence of Quaternary marine sediments and present-day marine intrusion. The brackish groundwaters that are related to old raised beaches showed a low Cl/Br ratio. Areas affected by marine intrusion had Cl/Br ratios similar to seawater and higher than in other areas along the coastal zone. At some points on the delta, a mixture of brackish water and recharge water was detected--the recharge water has a sulfate facies, which causes a drop in the Cl/Br ratio and changes the general character of the water in the coastal zone. The coastal zone contains silty-clay intercalations that favor processes of ion exchange, anthropogenic pollution also occurs and together these processes hamper the interpretation of all the processes.

Mapping groundwater quality variables using PCA and geostatistics: a case study of Bajo Andarax, southeastern Spain

Abstract A case study is presented for the application of statistical and geostatistical methods to the problem of estimating groundwater quality variables. This methodology has been applied to the investigation of the detrital aquifer of the Bajo Andarax (Almería, Spain). The use of principal components analysis is proposed, as a first step, for identifying relevant types of groundwater and the processes that bring about a change in their quality. As a result of this application, three factors were obtained, which were used as three new variables (VI: sulphate influence; V2: thermal influence; and V3: marine influence). Analysis of their spatial distribution was performed through the calculation of experimental and theoretical variograms, which served as input for geostatistical modelling using ordinary block kriging. This analysis has allowed a probabilistic representation of the data to be obtained by mapping the three variables throughout the aquifer for each sampling point. In this way, one can evaluate the spatial and temporal variation of the principal physico-chemical processes associated with the three variables VI, V2 and V3 implicated in the groundwater quality of the detrital aquifer.

Environmental control for determining human impact and permanent visitor capacity in a potential show cave before tourist use

Cave temperature monitoring was carried out in the Cueva del Agua de Iznalloz, Granada, Spain, a cave that has great tourist potential and which has been maintained under natural conditions for over 30 years. The cave temperature under natural conditions was used to identify possible anthropogenic influences, in order to distinguish these from the variations directly related to natural changes. In particular, the relative influence of external weather conditions, thermal modification caused by visitors and the subsequent thermal recovery of the cave were identified. In addition, controlled experiments investigated the effect of two large-scale visits (980 and 2088 visitors day -1 ) to the cave interior, before any tourist activities in the cave were undertaken. Correlation and spectral analyses of time series were used to determine the thermal behaviour of the cave over time. The effect of both mass visits on the air temperature in the interior of the cave was very rapid (2.5 min). The maximum perturbation of air temperature within the cave during the two experiments was after 30 and 70 min. The memory effect for temperature whilst the cave was open to the public was estimated to be 5-6 h, whilst the response to external meteorological changes exceeded one week. A permanent visitor capacity of 53 people ensures that the natural cave temperature can be regained within 4-5 h. The cave can only support small groups of visitors, not the massive visits characteristic of show caves.

Boron and the origin of salinization in an aquifer in southeast Spain

Abstract The analysis of the occurrence of boron in relation to other ions (Cl − and SO 4 2− ) in the groundwaters of the Lower Andarax river reveals that this element is basically derived from the dissolution of evaporite sediments and geothermal processes. This study confirms that the geothermal anomalies favour the mobilization of boron although this factor does not exclusively determine the high content present in some areas. The maximum boron concentrations are associated with zones where the salinity is higher and is related to the dissolution of evaporite salts.

Geometry and dynamics of the freshwater-seawater interface in a coastal aquifer in southeastern Spain

Abstract The contact between freshwater and seawater in coastal aquifers is studied using a relatively simple model for homogeneous aquifers. However, for real aquifers it is not so simple. The desalination plant built to supply water to the city of Almería is situated over the aquifer in the southern part of the River Andarax Delta. Its design capacity is 1100 L s−1, and it is supplied from boreholes pumping water from beneath the freshwater—seawater contact in this aquifer. Well logs kept over a period of two years have allowed us to accurately define the interface geometry of the freshwater—seawater contact. Lithological data collected from 31 boreholes have also indicated the existence of strata with low hydraulic conductivity, within others of high conductivity. During a simultaneous pumping test of six wells with 690 L s−1 total discharge, electrical conductivity measurements showed the influx of seawater 6–10 m below sea level and a drawdown of the interface in the piezometers closest to the pumping wells.

Hydrogeochemical processes as environmental indicators in drip water: study of the Cueva del Agua (Southern Spain)

INTRODUCTION The hydrodynamic processes and mechanisms involved in rain infiltration and recharge in karst terrains can be identified and quantified by measuring seepage from cave stalactites. Unlike the diffuse recharge that prevails in porous media, the processes and mechanisms involved in recharge of a highly heterogeneous, karstic environment are not easily characterized. A great variety of factors controls the quantity and composition of the water inflow into caves. Climate determines timing and quantity of water input, and the proportion that falls as snow, which could be recycled by evaporation. Climate (and thus altitude and topography) influence vegetation cover, whose development strongly affects the chemistry of the carbonate system and soil properties (Fairchild et al., 2007). The aquifer itself has a complex response

Groundwater–wetlands interaction in coastal lagoon of Almería (SE Spain)

Water resources management in coastal wetlands requires the degree of interdependence between groundwater and terrestrial ecosystems to be known. This is especially so in semiarid areas where surface inflows are restricted, marine influence is marked and the evaporation rate is high. Thus, chemistry of surface waters is very variable in the Cerrillos-Punta Entinas wetlands system. Using classical hydrogeochemical tools, the main processes that favor a diversity of water types were described, related to: presence of salt deposits on the lagoon beds, marine origin of the water, and local influence of groundwater. All these factors make it difficult to establish what reference conditions should be used to define “good” water quality of the surface waters—as required by the Water framework directive—and to understand the influence of groundwater on these coastal wetlands. Knowledge about the influence of the different interaction of these factors on the hydrogeochemical dynamics is required for the sustainable management of this protected natural site.

The Relationship Between Surface Waters and Groundwaters in the Coastal Wetlands of Campo de Dalías (Almería, SE Spain) and Their Importance for Sustainable Water Management

Water resources management in coastal wetlands requires knowledge of the degree of interdependence between groundwater and terrestrial ecosystems. This is especially so in semi-arid areas where surface inflows are restricted, marine influence is marked and the evaporation rate is high. In the Cerrillos-Punta Entinas wetland, the surface water quality is highly variable. Using hydrogeochemical tools, the main processes that favor the diversity of water types are described, arising from: the presence of salt deposits on the pool beds, the predominantly-marine origin of the water, and the local influence of groundwater. Understanding the influence of each process assists in determining how best to manage the water resources of this protected natural space in a sustainable way.

Constraining Geostatistical Simulations of Delta Hydrofacies by Using Machine Correlation

In some hydrogeology applications, the only subsurface geological information available comes from a small number of boreholes from which hydrofacies have been intersected and identified. Geostatistical simulation is a widely used stochastic technique for generating a set of possible hydrofacies images that cover the range of the complexity and heterogeneity of the structures. However, the uncertainty due to the very sparse data may be significant to the extent that the simulated images cover an unrealistically large range of possibilities for the hydrofacies characteristics. In such cases it may be desirable to constrain the simulations so as to provide a more realistic, or plausible, set of simulations. In the absence of wireline logging, outcrops, geophysics, production data or any other types of hard data, we propose the use of machine numerical correlation between hydrofacies at the boreholes as a means of constraining the range of plausible simulations. The procedure is used to simulate delta hydrofacies in a coastal aquifer in Almeria (Southern Spain) where the variability of the hydrofacies is critical for managing problems related to seawater intrusion.

Influence of Interactions of Surface Waters: Groundwaters on the Chemistry of Surface Waters in the River Andarax Catchment (Almería, SE Spain)

Interactions between surface water and groundwater (SW-GW) in the Andarax catchment are complex and encourage a diversity of surface waters in the three longest watercourses. The headwaters of the river Andarax flow continuously, but it is temporal in its middle reaches and ephemeral in its lower reaches; these three reaches demonstrate the effect of GW-SW dependence. Water quality is also affected by increases in nitrate and salinity in different stretches. The middle reach of the river Nacimiento carries a permanent flow due to a diffuse discharge of groundwater. In the Tabernas rambla (gulley), there is a perennial saline water flow associated with a discharge of saline groundwater, but this is not continuous over the length of the watercourse. Understanding the diversity of situations linked to GW-SW interactions is essential in this semi-arid area if its water resources are to be managed properly; therefore, these interactions need to be borne in mind when considering the water quality indicators of the surface waters.