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.

Abstract: One of the major causes for the deterioration of water quality bearing heavily on the water crisis in Israel is the ongoing contamination of its water resources by saline water bodies. The present paper reviews the geochemical processes forming saline water, lists and explains certain chemical and isotopic parameters which enable understanding these processes and describes the saline groundwater bodies and various salinization phenomena occurring in the country’s various aquifers. Deterioration of groundwater in Israel is caused by numerous natural processes such as encroachment of sea water, migration of connate, highly pressurized brines penetrating into fresh groundwater, by subsurface dissolution of soluble salts originating in surrounding country rocks and by water-rock interaction. In addition to sea water, two saline water bodies were identified as the main factors causing salinization of fresh groundwater: (a) Ca-chloride brines encountered in the Jordan-Dead Sea Rift Valley, in various parts of the Negev and of the Coastal Plain, and (b) Na-chloride saline water identified in the subsurface of the Negev and in the southern part of the Coastal Plain. Intensive exploitation of groundwater in Israel has disturbed the natural equilibrium which prevailed between fresh and saline water. The newly established groundwater flow regimes have facilitated the migration of saline water bodies, their participation in the active hydrological cycle and the progressive contamination of fresh groundwater. These processes which were not anticipated by planners and water resources managers emphasize that large-scale groundwater exploitation was undertaken without giving sufficient consideration to the occurrence and subsurface migration of saline water and brines.

Abstract: Subsurface brines are abundant in the Sichuan Basin, China. Five brine-bearing aquifers have been identified within rocks of Triassic age in the central part of the basin. These are of two types: brine-bearing clastic and brine-bearing carbonate aquifers. Brines in this region have high total dissolved solids and chemical species that are different from those of evaporatively concentrated seawater. Deep formation brines in clastic aquifers, in which evaporites do not exist, are characterized by high concentrations of Ca, Sr, Ba, Br and I, low concentrations of Mg and K, and lack of SO4, and are dominated by the NaCaCl type. Brines in carbonate aquifers, which have interbeds of evaporites, are characterized by high total dissolved solids, low concentrations of Ca, Mg and SO4, and lack of Ba, and are of the NaCl type. The brines in clastic aquifers originate from connate continental sedimentary waters mixed with marine waters; membrane filtration through shales has played an important part in modifying the chemical compositions and increasing the salinity of the brines. Those in carbonate aquifers are bittern marine sedimentary waters, with chemical compositions mainly controlled by precipitation of evaporites.