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Llopis-Albert, C., Merigó, J. M., & Xu, Y. (2016). A coupled stochastic inverse/sharp interface seawater intrusion approach for coastal aquifers under groundwater parameter uncertainty. Journal of Hydrology, 540, 774–783.
Abstract: This paper presents an alternative approach to deal with seawater intrusion problems, that overcomes some of the limitations of previous works, by coupling the well-known SWI2 package for MODFLOW with a stochastic inverse model named GC method. On the one hand, the SWI2 allows a vertically integrated variable-density groundwater flow and seawater intrusion in coastal multi-aquifer systems, and a reduction in number of required model cells and the elimination of the need to solve the advective-dispersive transport equation, which leads to substantial model run-time savings. On the other hand, the GC method allows dealing with groundwater parameter uncertainty by constraining stochastic simulations to flow and mass transport data (i.e., hydraulic conductivity, freshwater heads, saltwater concentrations and travel times) and also to secondary information obtained from expert judgment or geophysical surveys, thus reducing uncertainty and increasing reliability in meeting the environmental standards. The methodology has been successfully applied to a transient movement of the freshwater-seawater interface in response to changing freshwater inflow in a two-aquifer coastal aquifer system, where an uncertainty assessment has been carried out by means of Monte Carlo simulation techniques. The approach also allows partially overcoming the neglected diffusion and dispersion processes after the conditioning process since the uncertainty is reduced and results are closer to available data.
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Magaritz, M., Nadler, A., Kafri, U., & Arad, A. (1984). Hydrogeochemistry of continental brackish waters in the southern Coastal Plain, Israel. Chemical Geology, 42(1), 159–176.
Abstract: The southern Coastal Plain in Israel incorportates a transitional fringe of the desert in which three different chemical types of groundwater are found: (1) near-surface waters from springs along the Besor River course: (2) shallow- to moderate-depth waters from the slightly westward-dipping Pleistocene coastal aquifer (this aquifer, which consists of sandstone layers of the Kurkar Group, is recharged in the Coastal Plain); and (3) deep waters of the westward-dipping Upper Cretaceous Judea Group carbonates, which are recharged in the mountains in the east. A thick aquiclude of Upper Cretaceous-Tertiary rocks separates the Judea Group aquifer from the overlying coastal aquifer in the southern Coastal Plain. Isotopically light oxygen and depleted deuterium characterize the Judea Group waters, as expected from high-altitude recharge. The isotopic composition of the Coastal Plain waters is variable, but for the most part enriched in 18O and D. Within the southern Coastal Plain aquifer a southern subgroup comprises waters more depleted in heavy isotopes than those of either the northern or eastern subgroups. The Besor waters are isotopically similar to the Judea Group waters, reflecting their origin in the mountain region, and flow through the surficial river gravels and sands. It is suggested that leakage of the Besor waters into the underlying southern Coastal Plain aquifer results in mixing of the two water types. The most prominent chemical feature characterizing the groundwater of the southern Coastal Plain is Na+Cl− \textgreater 1. This Na+Cl− ratio can be maintained only by a continuous input from a non-marine source of Na. The most plausible source of this Na is the dissolution of feldspar derived from the windblown loess deposits which cover the area and/or leaching of trona minerals found in the unsaturated zone, combined with base-exchange processes.
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Nadler, A., Magaritz, M., & Mazor, E. (1980). Chemical reactions of sea water with rocks and freshwater: Experimental and field observations on brackish waters in Israel. Geochimica et Cosmochimica Acta, 44(6), 879–886.
Abstract: Four major processes are observed to take place in the coastal aquifer of Israel, detectable even in the short times of water contact with the carbonate-containing host rocks. Three are chemical reactions, Ca2+-Mg2+ exchange, Na+-Ca2+ or Na+-Mg2+ base exchange, SO2−4 reduction and the fourth is dilution by freshwater. These reactions and their effects on the chemical composition of the waters were demonstrated experimentally. The range of chemical changes observed in the laboratory experiments overlap the range of the studied natural waters. This indicates that simulation of geologically long-term rock-water interaction could be achieved in laboratory experiments even at low temperatures.
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Pacheco, F. A. L., & Szocs, T. (2006). “Dedolomitization reactions” driven by anthropogenic activity on loessy sediments, SW Hungary. Applied Geochemistry, 21(4), 614–631.
Abstract: In the Szigetvár area, SW Hungary, shallow groundwaters draining upper Pleistocene loess and Holocene sediments are considerably contaminated by domestic effluents and leachates of farmland fertilizers. The loess contains calcite and dolomite, but gypsum was not recognized in these sediments. The anthropogenic inputs contain significant amounts of Ca and SO4. The Ca from these anthropogenic inputs is promoting calcite growth, with concomitant consumption of carbonate alkalinity, undersaturation of the system with respect to dolomite, and dolomite dissolution; in brief, is driving “dedolomitization reactions”. Geochemical arguments supporting the occurrence of “dedolomitization reactions” in the area are provided by the results of mass balance and thermodynamic analyses. The mass balances predicted the weather sequence dolomite\textgreatercalcite\textgreaterplagioclase\textgreaterK-feldspar, at odds with widely accepted sequences of weatherability where calcite is the first mineral in the weathering sequence. The exchange between calcite and dolomite can be a side effect of “dedolomitization reactions” because they cause precipitation of calcite. The thermodynamic prerequisites for “dedolomitization reactions” are satisfied by most local groundwaters (70%) since they are supersaturated (or in equilibrium) with respect to calcite, undersaturated (or in equilibrium) with respect to dolomite, and undersaturated with respect to gypsum. The Ca vs. SO4 and Mg vs. SO4 trends are also compatible with homologous trends resulting from “dedolomitization reactions”.
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Sebben, M. L., Werner, A. D., & Graf, T. (2015). Seawater intrusion in fractured coastal aquifers: A preliminary numerical investigation using a fractured Henry problem. Advances in Water Resources, 85, 93–108.
Abstract: Despite that fractured coastal aquifers are widespread, the influence of fracture characteristics on seawater intrusion (SWI) has not been explored in previous studies. This research uses numerical modelling in a first step towards understanding the influence of fracture orientation, location and density on the extent of seawater and accompanying patterns of groundwater discharge in an idealised coastal aquifer. Specifically, aquifers containing single fractures or networks of regularly spaced fractures are studied using modified forms of the Henry SWI benchmark problem. The applicability of equivalent porous media (EPM) models for representing simple fracture networks in steady-state simulations of SWI is tested. The results indicate that the influence of fractures on SWI is likely to be mixed, ranging from enhancement to reduction in seawater extent and the width of the mixing zone. For the conceptual models considered here, vertical fractures in contact with the seawater wedge increase the width of the mixing zone, whereas vertical fractures inland of the wedge have minimal impact on the seawater distribution. Horizontal fractures in the lower part of the aquifer force the wedge seaward, whereas horizontal fractures located within the zone of freshwater discharge enhance the wedge. Inclined fractures roughly parallel to the seawater-freshwater interface increase the landward extent of seawater and fractures perpendicular to the interface inhibit the wedge. The results show that EPM models are likely inadequate for inferring salinity distributions in most of the fractured cases, although the EPM approach may be suitable for orthogonal fracture networks if fracture density is high and appropriate dispersivity values can be determined.
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