Fernando Sola

The anthropogenic impact on Mediterranean karst aquifers: cases of some Spanish aquifers

Mediterranean karstic aquifers are a major source of water supply for drinking water and agricultural use. In semiarid areas, the risk of causing an intensive exploitation is high, leading to degradation processes of water quality, not only due to limited agricultural activities developed on the karstic rocks—being generally poorly developed soils—but to the presence of deep evaporates which can be mobilised, or because of being coastal aquifers where seawater intrusion can progress rapidly. Moreover, karstic massifs constitute often positive reliefs that can generate barriers for civil works, more and more saved by building sophisticated tunnels; such works can affect the quantity and quality of the waters from the karst. Five examples of human impacts on some karst aquifers in SE of Spain are shown in this paper, three of them with impacts on water quality and the other two correspond to the impact of tunnels in high-speed trains drilling below the water table.

An oceanographic survey for the detection of a possible Submarine Groundwater Discharge in the coastal zone of Campo de Dalias, SE Spain

The Campo de Dalias, in south-eastern Spain, is an area of important economic activity linked to agriculture and tourism, both of which have exacted fierce exploitation of aquifer water. The recovery of one of these aquifers in recent years has even triggered fresh water discharges into the sea. An oceanographic survey was undertaken along the coastline in order to detect possible Submarine Groundwater Discharge (SGD). Salinity and temperature data were collected on the seasurface, as well as in 51 vertical profiles. These results suggest the existence of a thermohaline anomaly in the area of the port of Aguadulce possibly due to submarine groundwater discharges.

A first inventory of gypsum flora in the Palearctic and Australia

Gypseous substrates are well-recognised as supporting distinctive and unique flora assemblages, including numerous gypsum endemic (gypsophile) species. Along with these, others are also frequent although their presence is not restricted to gypsum; they show a clear preference for them (gypsocline). While this phenomenon (gypsophily) has been studied regionally, and various hypotheses put forward to explain it, there has been little global synthesis. We present a preliminary check-list on the gypsophile and gypsocline flora of the Palaearctic and Australian areas as a part of a project to develop a global checklist of the World’s gypsophytes, which can broaden our ecological and biogeographical understanding of these unique environments. The database contains 935 taxa spanning 54 countries. The Irano-Turanian region —and to a lesser extent the Mediterranean region— emerged as the richest territories in terms of gypsophile species; this richness was much reduced in the Saharo-Arabian and, especially in the Eurosiberian regions. The factors that can modulate the richness of gypsophytes in a region are discussed and have been distributed into four groups: a) geological and edaphic factors; b) factors linked to the insular nature of outcrops; c) climatic variables and their interaction with the soil; d) biogeographical factors. The importance of those factors linked to insularity and, especially, to water availability is emphasized. Because the soil structure of many gypsum outcrops reduces water ability to plants, such outcrops can be regarded as “dry-islands” surrounded by less xeric substrates. The fact that gypsophytes can be grouped within a few major flowering plant clades across continents, confirms their pre-adaptations to these harsh and unique environments. Our work provides a preliminary database for exploring ecological and biogeographic issues relating to gypsophily, and we hope it will stimulate global interest in these valuable ecosystems.

Impacts of agricultural irrigation on groundwater salinity

Agricultural irrigation represents the main use of global water resources. Irrigation has an impact on the environment, and scientific evidence suggests that it inevitably leads to salinization of both soil and aquifers. The effects are most pronounced under arid and semi-arid conditions. In considering the varied impacts of irrigation practices on groundwater quality, these can be classed as either direct—the direct result of applying water and accompanying agrochemicals to cropland—or indirect—the effects of irrigation abstractions on groundwater hydrogeochemistry. This paper summarizes and illustrates through paradigmatic case studies the main impacts of irrigation practices on groundwater salinity. Typically, a diverse range of groundwater salinization processes operating concomitantly at different time scales (from days to hundreds of years) is involved in agricultural irrigation. Case studies suggest that the existing paradigm for irrigated agriculture of focusing mainly on crop production increases has contributed to widespread salinization of groundwater resources.

Numerical modelling of a forced gradient tracer test undertaken under non-ideal conditions

Pumping and tracer tests are common methods for the characterization of the aquifers used for supplying desalination plants. A case study is presented from Almería in SE Spain in which the unexpected movement of fine sediment caused by continuous pumping and incomplete removal of the drilling mud in the boreholes makes it impossible to conduct and interpret a standard tracer test. A modified tracer test was therefore performed in the unconsolidated clastic aquifer at this site and then interpreted numerically using two conceptual models: (1) a homogeneous model representing an unaltered medium; (2) a heterogeneous model incorporating an alteration zone around the borehole. The heterogeneous model produced a better calibration with more realistic parameter values for the aquifer and silty material (permeability, specific storage, effective porosity, dispersivity). The aquifer was characterized as a poorly sorted detrital sedimentary deposit with a large quantity of silt in the matrix. The conclusion is that advective transport dominates almost all the tracer movement. However, dispersive and/or diffuse transport determine the tail length of the breakthrough curve.