Links between the presence of snowpacks and groundwater recharge – Simulation results for the territory of Slovenia

The implementation process of the EU water legislation (EU WFD, EU GWD) has put pressure on hydrogeologists to create, analyse and disseminate groundwater recharge maps in high temporal and spatial resolution for sustainable water management. The distributed water balance model mGROWA is currently applied in several European countries in order to create such maps. Applying mGROWA to country-specific prevailing climatic and hydrogeological conditions requires adaptations of the methodology with regard to the model setup and implementation. In contrast to many lowland regions in Western and Southern Europe, groundwater recharge in many Slovenian aquifers is limited during winter months due to water retention in snowpacks. Against this background the mGROWA model has been enhanced in a Slovenian-German research cooperation by procedures for the simulation of relevant processes associated with formation and melting of snowpacks. In combination with the multi-layer soil water balance module which was already implemented in mGROWA, this new feature enables a realistic simulation of inner-annual variations of groundwater recharge patterns in European alpine and highland areas in daily time-steps on a 100 m grid.In this contribution we briefly introduce the mGROWA methodology and the newly implemented snowpack module. Subsequently, model results for the reference period 1971-2014 are shown. This includes on one hand the evaluation of the simulated snowpack presence by using observations at about 400 sites and an assessment of the evolution of days with snowpack during winter. On the other hand, simulated groundwater recharge rates are evaluated with observed stream flow hydrographs and base-flow derived from these. In this context, also the impact of simulating temporal snowpack presence on groundwater recharge patterns is presented and discussed with a few examples. Finally, the consequences of addressing snowpacks in groundwater recharge assessments will be discussed with regard to the implications for management strategies for sustainable use of groundwater resources in Alpine regions

Can the structure of dormant cambium and the widths of phloem and xylem increments be used as indicators for tree vitality?

We investigated the structure and width of the dormant cambium and of the increments of phloem and xylem of Quercus robur to estimate their potential as indicators for tree vitality. The samples were taken from three woodlands, two in Slovenia [Krakovo forest (KRA) and Murska Suma (MUS)] and one in Croatia [Kobiljak (KOB)], with reported tree decline. The number of dormant cells seems to reflect the initial capacity of the cambium to accomplish cell division. With the exception of two trees at KRA, cell production was always higher on the xylem side than on the phloem side. The annual phloem increments were narrower, less variable among trees and with clear lower and upper limits. With increased cambial cell productivity, the share of the xylem in the total annual radial increment increased following a curvilinear function. In trees with an annual radial increment >3.5 mm, the xylem size represented more than 90 % of the total radial growth. The anatomical variables analyzed show that the most limiting environmental conditions seem to prevail at KRA, whereas the conditions at MUS seem to be most favorable in terms of radial growth. Analysis of the width and structure of xylem and phloem increments, the number of dormant cambial cells and their inter-relationships can provide additional information on the vitality of oaks

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