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Processes such as urbanization, agricultural development and industrialization have led to increasing demand of groundwater resources resulting in pollution threats to groundwater in different ways, either as contaminant loads on the ground surface, or as seawater intrusion due to overexploitation of wells in the coastal zone. Two groundwater vulnerability indices are applied in this paper to assess the potential risk of groundwater contamination in the eastern delta of Nestos River, Greece. DRASTIC model is used in this paper to evaluate the groundwater vulnerability of the area with focus on agrochemical contaminants, more especially on nitrate pollution, since the region is highly cultivated. Additionally, GALDIT index is also applied to assess the vulnerability of the freshwater aquifer to seawater intrusion, as the extensive pumping of the coastal wells has led to this phenomenon. The vulnerability assessment showed that the study area experiences low to moderate groundwater vulnerability to agrochemical contaminants, as well as moderate to high vulnerability to seawater intrusion. The use of GIS for both vulnerability indices was found effective for the evaluation of each method in comparison to real field data.

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In this paper, the development of the conceptual and groundwater flow model for the coastal aquifer system of the alluvial plain of River Nestos (N. Greece), that suffers from seawater intrusion due to over-pumping for irrigation, is analyzed. The study area is a typical semi-arid hydrogeologic environment, composed of a multi-layer granular aquifers that covers the eastern coastal delta system of R. Nestos. This study demonstrates the results of a series of field measurements (such as geophysical surveys, hydrochemical and isotopical measurements, hydro-meteorological data, land use, irrigation schemes) that were conducted during the period 2009 to 2014. The synthesis of the above resulted in the development of the conceptual model for this aquifer system, that formed the basis for the application of the mathematical model for simulating groundwater flow. The mathematical modeling was achieved using the finite difference method after the application of the USGS code MODFLOW-2005.

In this study, we examined the efficiency of a kaolinite clayey soil to mitigate water repellency of a sandy soil with olive trees. The treatment was applied to the soil zone below the tree canopy, which displayed the highest degree of water repellency [average water drop penetration time (WDPT) value = 820 s]. Both dry (incorporated onto the top soil) and wet clay applications (after dispersion in irrigation water) were examined in a replicated experiment, with control trees being used for comparison. The application rate of the clayey soil was maintained in both cases (wet and dry mode) equal to 1 kg m−2, while the effect of subsequent wetting and drying cycles on the treatment performance was evaluated. The results of the study verify that clay application was effective to mitigate soil water repellency. Dry supplementation displayed low efficiency (26% reduction of the air‐dry WDPT compared with the control soil) within the first week of application. The efficiency of the dry‐clay treatment increased to 76% after applying three subsequent wetting and drying cycles. In comparison with the dry mode, the wet clay was efficient immediately after application (74% reduction of the WDPT), indicating that the limiting step in the overall process was clay dispersion. Based on the findings of this study, it was proposed that wet clay application is of interest for controlling soil water repellency in agricultural land. Copyright © 2016 John Wiley & Sons, Ltd.