Groundwater nitrate sources in alluvial aquifers: Isotope case study in Savinja Valley (Slovenia)

Abstract The chemical status of the shallow alluvial Savinja Valley groundwater body in Slovenia is poor, mainly due to the high concentration of nitrate in groundwater. This case study is therefore oriented in the assessment of groundwater vulnerability to nitrate pollution, as a base for the measure-planning processes. The article describes the use of isotope information of surface water and groundwater for the determination of possible sources of groundwater nitrate pollution. The isotope information of predominant soil and manure/septic waste nitrate origin, associated with other local physical and chemical boundary conditions and land use data, offers an interpretative support in the delineation of nitrate vulnerable zones

Comparison of the modeling results of nitrate concentrations in soil water below the root zone in the local and regional scale

The article presents a comparative analysis of the modeling results of nitrate concentrations in water below the root zone of the soil in the local and regional scale. In this research, the fild-scale DNDC (Denitrifiation – Decomposition) and the regional-scale GROWA–DENUZ (ger. Großräumiges wasserhaushalt – Denitrifiation im durchwurzelten Boden) models were applied to the study area of the shallow aluvial aquifer of the Spodnje Savinjska dolina in the central part of Slovenia. Using the concept of Hydrological Response Unit (HRU) and Cohen Kappa statistical analysis of the degree of agreement and assessment of the reliability of the results of spatial modeling of nitrate in soil water below the root zone, we determined and interpreted the areas of maximum agreement and disagreement of model results. A good agreement was found at the highest modeled concentrations of nitrate in soil water, whereas the greatest deviations were detected primarily in the lower part of the range. The main reasons for disagreement were differences in the estimation of the denitrifiation conditions in the anaerobic environments of gley-soils with the shallow groundwater and differences in fertilisation scenarios and agricultural practices

Groundwater recharge in Slovenia - Results of a bilateral German-Slovenian Research project

Groundwater is a resource of utmost strategic importance for Slovenia and Germany providing drinking water of good quality to its population. For decades, management of this key resource has received the highest priority of our national hydrological services. In the framework of the service activities in both countries, groundwater status in terms of quantity and quality has been observed and studied systematically for more than 50 years. In the eighties of the last century the first models forgroundwater recharge assessment at local and regional scale were developed. However, long time assessment of groundwater status and estimation of groundwater recharge for heterogeneous hydrogeology systems of entire countries were not available. In this respect the GROWA model, developed at the Agrosphere Institute of Research Centre Jülich, was one of the first groundwater recharge models that was applicable at the level of river basins and Federal States in Germany. The transfer and application of the GROWA model to groundwater systems of the Republic of Slovenia was a pioneering effort, establishing for the first time a groundwater recharge model covering the whole territory of Slovenia and not focusing on individual aquifers only, being the practice in Slovenia before. [...

Methodological contribution to geochemical subdivision of coal seams

The statistical analysis of geochemical data collected at Zasavje coal basin offered the possibility to use distribution characteristics of geochemical factors and clusters for subdivision and genetic interpretation of coal seams. In accordanceto sampling scheme for variance analysis the interval samples of coal and bearing rocks brought data on ultimate, proximate and atomic emission spectrometric analysis, and silicate analysis of coal ash. Variability of all measured variableswas studied on regional, vertical, sampling and analytical level. After factor analysis of 23 selected variables terrigenous (K, Cu, V, Cr, ash, Zn, Be, Co, AI2O3, SiO2), carbonate (Mn, CO2, Fе203, Ni), sulphide-sulphate (sulphide and sulphate sulphur, Fе203), nitrogen-hydrogen (0, N, H) and typomorphic factor (Sr,Ca, organic sulphur, C, Ba) have been determined. Five synthetic variables (factors)explain 79% of the total variance. Yet on the basis of the first three factor values the samples can be arranged by use of cluster analysis into sample groups (clusters), which represent various geochemical segments of coal seams.By using above presented methodological guidelines which are based on crosssections of individual coal-bearing basins structural units, the future multidisciplinary research can lead to genetic model of Slovenian coal basins. Presented article is a contribution to look after best possible geochemical methodology which purpose is to reach this aim

Groundwater vulnerability to nitrate pollution of alluvial aquifers in Slovenia – Lower Savinja Valley case study

The article introduced an upgraded approach to assessing the groundwater vulnerability to nitrate pollution. By using the results of fild measurements and process-based models outputs, author takes into account effects of nitrogen biogeochemical processes, that were hitherto underestimated in the evaluation schemes. The upgraded methodological self-validated approach to vulnerability assessment in Lower Savinja Valley case study increases reliability and thus effectiveness of decision-making in the water management. This was achieved by using the process-based models outputs in the new pattern classifiation schemes with the predictions of pollution phenomena. Spatial prediction of groundwater nitrate pollution probability and vulnerability classifiation of the study area in Lower Savinja Valley was assessed by weights-of-evidence model (WofE). The increased degree of probability for the groundwater contamination with nitrates was determined for 62.5 percent of the aquifer area of the Lower Savinja Valley. About 27 percent of the most nitrate vulnerable areas in Lower Savinja Valley need groundwater nitrate mitigation through land-use measures and public sewage system construction

Assessment of groundwater quantitative vulnerability to climate change in Slovenia

Assessment ofthe potential impact of climate change on groundwater recharge and availability of groundwater resources is as essential in Slovenia as it is elsewhere. Adaptive planning is of immense importance when aiming for reduction of negative impacts, even more so in areas with the highest groundwater exploitation levels and the lowest adaptive capacity. We have assessed quantitative groundwater vulnerability to climate change through potential impact and adaptive capacity indicators for all groundwater bodies in Slovenia. High and moderatly high quantitative groundwater vulnerability can be observed in merely 9 % of Slovenian territory. The highest quantitative vulnerability was accounted to shallow alluvial groundwater bodies in the northeastern part of the country, where the annual change in groundwater recharge due to climate change until the middle of this century is expected to represent more than a quarter of the current average annual groundwater extraction

Determination of nitrogen reduction levels necessary to reach groundwater quality targets in Slovenia

Within a collaborative project between Slovenian Environment Agency (ARSO) and Research Center Jülich (FZJ), nitrogen reduction levels necessary to reach groundwater quality targets in Slovenia were assessed. For this purpose the hydrological model GROWA–DENUZ was coupled with agricultural N balances and applied consistently to the whole territory of Slovenia in a spatial resolution of 100 × 100 m. GROWA was used to determine the water balance in Slovenia for the hydrologic period 1971–2000. Simultaneously, the displaceable N load in soil was assessed from agricultural Slovenian N surpluses for 2011 and the atmospheric N deposition. Subsequently, the DENUZ model was used to assess the nitrate degradation in soil and, in combination with the percolation water rates from the GROWA model, to determine nitrate concentration in the leachate. The areas showing predicted nitrate concentrations in the leachate above the EU groundwater quality standard of 50 mg NO3−/L have been identified as priority areas for implementing nitrogen reduction measures. For these “hot spot” areas DENUZ was used in a backward mode to quantify the maximal permissible nitrogen surplus levels in agriculture to guarantee a nitrate concentration in percolation water below 50 mg NO3−/L. Model results indicate that additional N reduction measures should be implemented in priority areas rather than area-covering. Research work will directly support the implementation of the European Union Water Framework Directive in Slovenia, e.g., by using the maximal permissible nitrogen surplus levels as a framework for the derivation of regionally adapted and hence effective nitrogen reduction measures

Groundwater quantitative status assessment in Slovenia

The framework for the integrated water management of the entire EU area has been set, when the European Parliament and Council passed the Directive 2000/60/EC in 2000. According to the directive, the evaluation of meeting the environmental objectives is based also upon the assessment of quantitative and chemical status of individual groundwater body.The assessment of quantitative status of groundwater bodies under the Groundwater Directive of EU is based on the definition of the available groundwater quantity.Thisisalong period mean annual renewable quantity of water in the groundwater body, reduced by the quantity of the long period annual groundwater discharge, which is required for sustaining ecological objectives concerning surface water bodies and preservation of the ecosistems, connected with the groundwater bodies.Methodological approach and the results of the first groundwater quantitive status assessment for 21 groundwater bodies in Slovenia are given in this paper. The assessment of the available groundwater quantity in Slovenian groundwater bodies in the period from 1990 to 2001 are 1,43 ⋅ 109 m3 per year, and 727,4 m3 per capita per year respectively. In the year 2002 abstracted groundwater (0,23 ⋅ 109 m3 per year) represents 15 percent of the available groundwater reserves in Slovenia. For all Slovenian groundwater bodies quantitative status was assessed as good

Model-based assessment of groundwater recharge in Slovenia

The implementation process of the EU water legislation (EU WFD, EU GWD) has put pressure on environmental managers to create, analyse and disseminate hydrological data in recent years. In this context, distributed hydrological model results at the macro scale (>10,000 km2) have gained importance for the Environment Agency of the Republic of Slovenia, too. Within a joint project the distributed water balance model GROWA, developed for Germany, has been adapted to Slovenia by re-calibrating the routine for determining the average annual groundwater recharge rate. This routine consists mainly of a base flow index approach (BFI). This BFI is based on 41 different site conditions in Slovenia, whereas lithology dominates the recharge process. This paper outlines the general GROWA approach, the required input data, and the calibration process. Validated model results for the period 1971–2000, especially total runoff and base flow, are presented and discussed. These results have been used already for practical water management issues in Slovenia on European, national and regional level. It is shown that Slovenian groundwater resources exhibit high regional and seasonal variability. Tendencies of more frequent and more pronounced droughts have been detected. As demonstrated by the results GROWA is a valuable tool for the spatially distributed assessment of groundwater recharge in Slovenia