This study was conducted in order to investigate possible quality changes in Cyprus’ groundwater resources over a 10-year period of pumping and to check the suitability of primary irrigation water. Water samples (n = 890) from private wells in agricultural areas were analyzed from 2009 to 2018 to determine various physicochemical properties. The sodium adsorption ratio (SAR) and residual sodium carbonate (RSC) were also calculated to evaluate potential soil degradation issues. Sodium, chloride and sulphate were found to be the predominant ions in groundwater. Quality evaluation showed possible restrictions in groundwater use for irrigation in relation to its salt content and the toxicity of specific ions having adverse effects on sensitive and several moderately sensitive crops. In particular, an increasing trend was observed in pumped groundwater for boron ion concentrations. Nevertheless, all samples evaluated were suitable for irrigation in terms of soil sodicitation and soil infiltration rate. This study indicates that in order to maintain long-term agricultural sustainability it is imperative to develop strategic plants to mitigate the adverse effects of water-pumped quality deterioration on soils and crops. Precision agriculture techniques may be adapted for better water and nutrient input/output management, thus protecting groundwater from salinization in agricultural areas. These results, among others, may be a useful tool to enhance the ability of Cyprus’s agricultural water sector to adapt to observed and anticipated climate impacts.

<p>Denitrification potential is an important parameter to know for adequate and efficient management and assessment of groundwater vulnerability and chemical status. Denitrification removes nitrate in groundwater, but the denitrification capacity is highly variable in space and time, and it may be used up with time. When linking pressure and impact the effect of partial or complete denitrification and denitrification capacity should be taken into account. In some areas, denitrification is seen as an advantage, allowing higher N release below soil without leading to a decrease of the groundwater quality and eventually concentrations in groundwater higher than the WFD and DWD threshold values, which EU member states have to establish to protect drinking water and groundwater dependent terrestrial and associated aquatic ecosystems.    </p><p>Within the GEOERA HOVER project, the aim was to assess the spatial extent and importance of denitrification. The studied cases permitted at a first step to highlight the heterogeneities of the approaches due to the variability of information obtained i.e. the likelihood of denitrification, depth and thickness of redox transition zone, complete denitrification status. The parameters used to define the denitrification vary also from one country to another based on a large set of redox sensitive ions (Eh, O<sub>2</sub>, NO<sub>3</sub>, NO<sub>2</sub>, Fe, Mn, SO<sub>4</sub>, CH<sub>4</sub>, δ<sup>18</sup>O<sub>-NO3</sub> et δ<sup>15</sup>N-<sub>NO3</sub>, H<sub>2</sub>S or N<sub>2</sub>). Some of these parameters can be accessed by standard methods in most laboratories, used for groundwater quality monitoring, while others require specialized analysis and interpretations.</p><p>Considering groundwater and hydrogeological data available in most of the EU countries, a simple method is proposed in order to classify the monitoring points into three classes: oxic, anoxic and mixed. After being tested in different well-known areas the method will be applied in various lithologies and hydrogeological contexts The proposed method will enable the development of European maps supporting groundwater quality management across Europe.</p>

<p>Due to continuous changes in the meteorological conditions of Mediterranean regions, it is becoming increasingly important to improve knowledge of hydrological and hydrogeological recharge processes and their dependency on climate conditions to adapt the use of limited water resources. Within the IsoMed project (isotope hydrology in Mediterranean areas), soil profiles were sampled in November 2018 and February 2019, from various hydrogeological settings in Cyprus to estimate groundwater recharge using stable isotope equilibration methods combined with soil water balance modeling. A total of 11 soil profiles were taken from the Troodos massif (Galata and Platania) and the Mesaoria plain in Deftera, Nicosia. A vertical profile of stable isotopes has been determined with a 2 cm resolution and measured with Tunable Diode Laser spectrometry. Percolation through the soil profile has been estimated based on the convolution of a seasonal input function using advection-dispersion transport models. In Galata, groundwater percolation estimates range from 20-30 mm/y on clayey soil with natural vegetation to 100-120 mm/y at an irrigated terraced orchard. The results in Platania vary from 20-60 mm/y at steep hillslopes under natural vegetation and amount to 220-340 mm/y in the root zone at the irrigated site with olive trees in Deftera. The comparison of groundwater percolation rates based on stable isotope profiles with those derived from soil water balance modeling indicates a significant bias. While percolation rates correspond well to results obtained from a daily soil water balance model for irrigated fine-grained soils in the plain, recharge rates obtained from stable isotope profile methods on coarse-grained hillslopes tend to be much lower than expected. The observed bias suggests that stable isotope methods, regardless of water extraction or equilibration technique, mainly record the isotope signal of matrix flow. Thus, macro-pore and preferential flow components in coarse-grained soils may not be accounted for. Data collected from the same profiles in late autumn and spring suggest that macro-pore and preferential flow constitute a major component of percolation in coarse-grained shallow hillslope soils of Troodos indeed, without leaving measurable isotope traces in the soil water profile. Additional approaches need to be applied in conjunction with methods based on the evaluation of soil water isotope profiles to overcome this limitation.</p>