Suchergebnisse

AbstractMembers of the Gulf Cooperation Council countries Bahrain, Kuwait, Oman, Qatar, Saudi Arabia, and the United Arab Emirates rely on desalination to produce water for domestic use. Desalination produces brine that may intrude into the aquifers to pollute the fresh groundwater because of the concentration gradient and groundwater pumping. Modeling the trends of saltwater intrusion needs theoretical understanding and thorough logical experimentation. The objective of this exercise was to understand the phenomenon of saltwater intrusion using an existing set of data analyzed with the convective–diffusion equation and the two-region mobile–immobile solution model. The objective was achieved by optimizing non-measurable solute transport parameters from an existing set of data generated from a series of logical miscible displacements of potassium bromide through sepiolite minerals and curve-fitting simulations. Assumptions included that solute displacements through sepiolite porous media and the related simulations represented the phenomenon of saltwater intrusion under non-equilibrium conditions of porous media mimicking the aquifers. Miscible displacements of potassium bromide were observed from a column of 2.0–2.8 mm aggregates of sepiolite over 4 ranges of concentration and at 11 displacement speeds under saturated vertical flow deionized water and vice versa. Breakthrough curves of both bromide and potassium ions were analyzed by a curve-fitting technique to optimize transport parameters assuming solute movement was governed (i) by the convective–diffusion equation and (ii) the two-region mobile–immobile solution model. Column Peclet numbers from the two analyses were identical for potassium ions but those for bromide ions were c. 60% greater from the two-region model than from the convective–diffusion equation. For the two-region model, dispersion coefficients were well defined and remained unchanged from the convective–diffusion equation for potassium ions but decreased for bromide ions. Retardation factors for bromide ions were approximately the same, but those for potassium ions, though > 1, were poorly defined. In order to design mitigation strategies for avoiding groundwater contamination, this study's findings may help model groundwater pollution caused by the activities of desalination of seawater, which produces concentrated liquid that intrudes into the coastal aquifer through miscible displacement. However, robust saltwater intrusion models may be considered in future studies to confirm the results of the approach presented in this exercise. Field data on the groundwater contamination levels may be collected to compare with simulated trends drawn from the saltwater intrusion models and the curve-fitting technique used in this work. A comparison of the output from the two types of models may help determine the right option to understand the phenomena of saltwater intrusion into coastal aquifers of various characteristics.

Climate change will result in rising sea level and, at least for the North Sea region, in rising groundwater table. This leads to a new balance at the fresh–saline groundwater boundary and a new distribution of saltwater intrusions with strong regional differentiations. These effects are investigated in several research projects funded by the European Union and the German Federal Ministry of Education and Research (BMBF). Objectives and some results from the projects TOPSOIL and go-CAM are presented in this poster.

In some Mediterranean karst areas, groundwater is often the only available supply for freshwater. Besides the contamination induced by human activities, coastal aquifers often suffer from the saltwater intrusion phenomenon, which can be enhanced by both extensive withdrawals and climatic changes. Establishing an effective set of regulatory and management measures to ensure the sustainability of coastal aquifers requires a deep knowledge about natural and anthropic stresses involved in groundwater dynamics. In this regard, a prior conceptualization of aquifer systems and a deeper characterization of balance terms through mathematical modelling are of paramount importance. In the gulf of Taranto (southern Italy), these issues are particularly pressing, as the multi-layered, carbonatic aquifer is the only available resource of freshwater and satisfies most of the human water-related activities. Especially during the last decades, proper management plans and decisions seem to be compelling, as the national government included Taranto in the list of the contaminated sites of national importance, due to the presence of highly-polluting activities nearby the Mar Grande and Mar Piccolo seawater bodies, whose relationship with the underground resources is matter of concern, as they host important freshwater springs. Furthermore, the Taranto area is particularly sensitive to the phenomenon of seawater intrusion, both for the specific hydrostratigraphic configuration and for the presence of highly water-demanding industrial activities. These problems, strictly related to the protection and preservation of groundwater quality and quantity, have triggered several actions. Among them, the Flagship Project RITMARE (la Ricerca Italiana per il Mare - the Italian Research for the Sea) took into account criticalities involving several environmental components within the Mar Piccolo ecosystem, including groundwater. In this thesis, a full charactrization of the multi-layered aquifer system of the whole Province of Taranto is presented, with the purpose of supporting monitoring activities, land-use plans and management decisions. The preliminary outcomes refer to the identification of the conceptual model, namely the reconstruction of the hydrostratigraphic structure of the underground and the qualitative assessment of the groundwater dynamics. The successive development of a numerical model permits to produce a tool for quantifying the hydrogeological balance and simulating the system response to climate or man-induced changes. Generally speaking, thorough evaluation of model adequacy and/or accuracy is an important step in the study of environmental systems, due to the uncertainties on hydrodynamic properties and boundary conditions and to the scarcity of good-quality field data. This commonly results in groundwater models being calibrated and often leads to the development of many candidate models that can differ in the analysed processes, representation of boundary conditions, distribution of system characteristics, and parameter values. In this framework, calibration of alternative models allowed to identify the main challenges which limit the reliability of model outcomes and test model adequacy while proposing a new calibration methodology, which represents tha major scientific contribution of this thesis.

We acknowledge the Royal Geographical Society (with IBG) Environment and Sustainability Research Grant for financial support for all field activities. Acknowledgments extend to the Kenyan Water Resources Authority (WRA) and the University of Aberdeen for supporting S. Oiro's PhD scholarship. We thank Security Officers and Government of Kenya Administrators who facilitated field access by informing the public of our presence in the area as well as the assistance by local casuals during the geophysical surveys. ; Peer reviewed ; Postprint

This study was supported by grant CGL2016-77503-R from the Ministry of Economy and Competitiveness (MINECO), cofounded by the European Regional Development Fund (ERDF) of the European Union (EU), and the RNM-369 research group of the regional government of Andalusia. The authors also thank the State Harbors (Ministry of Public Services, Government of Spain) for providing the sea temperature dataset. One of the authors conducted this work as part of the activities of the Aarhus University Centre for Water Technology, WATEC. Funding for open access charge: Universidad de Granada/CBUA. ; The temperature distribution in coastal aquifers is determined by the effect of different heat sources: surface water recharge, sea infiltration, and geothermal heat. In previous studies, the signal generated in groundwater by each source was individually studied, and in the case of geothermal heat, it was often not considered. This research is the first in considering all possible sources of heat in a coastal aquifer simultaneously by using a combination of field data and numerical modeling to present a reference model based on the characteristics of a real aquifer. The position of the freshwater-saltwater interface (FSI) and its effect on temperature distribution have been modeled considering variable-density flow, coupled heat and solute transport. This study broadens the theoretical knowledge of temperature distribution in coastal aquifers based on a sensitivity analysis of hydraulic and thermic parameters. Furthermore, a case study (the Motril-Salobreña aquifer) was modeled with field data calibration to test the applicability to real aquifers. The new insights gained through this study provide integrated knowledge of the temperature distribution in coastal areas and establish the basis for future research using heat as a tracer in seaside aquifers. ; Ministry of Economy and Competitiveness (MINECO) CGL2016-77503-R ; Junta de Andalucia RNM-369 ; Universidad de Granada/CBUA