Andrea Bačani

Quaternary Deposits as the Hydrogeological System of Eastern Slavonia

The area of eastern Slavonia, situated between the Drava and Sava rivers, comprises three geotectonic units: the eastern part of the Drava depression in the north, part of the Slavonia-Srijem depression in the south and the central —akovo-Vinkovci plateau together with the Vukovar plateau. These units are separated by deep faults that reach the base of the Tertiary sediments. The first 200 m of Quaternary deposits are saturated with fresh water. The aim of this study was to find out whether the faults form impermeable boundaries separating the waterbearing deposits into independent hydraulic systems, or if a singular hydraulic entity exists. Results of the analysis indicate that lithological continuity of the aquifers exists along the fault zones on the margins of the —akovo-Vinkovci and the Vukovar plateaux, which means that there is no impermeable hydraulic boundary on the watershed between the Sava and Drava river valley. The part of eastern Slavonia between the Sava and Drava rivers is one hydraulic system consisting of zones with different transmissivity values. In the zones of reduced transmissivity, the hydraulic connections are weakened, but not broken. Such zones exist not only along the fault zones of the —akovo-Vinkovci plateau and the Vukovar plateau, but also within the Sava and Drava depressions. The terrain morphology influenced formation of both the surface and the underground watershed, parallel to the extension of the —akovo-Vinkovci and Vukovar plateau. Therefore, within this single hydraulic entity, when the drawdown reaches the watershed due to excessive pumping, the watershed will be displaced from its natural position. Saaeetak U prostoru istone Slavonije, izme﷿u Save i Drave nalaze se tri geotektonske jedinice i to na sjeveru istoni dio Dravske potoline, na jugu dio Slavonsko-srijemske potoline, a izme﷿u njih —akovakovinkovaki i Vukovarski ravnjak. Ravnjaci su u morfolo„kom i struk turno-tektonskom pogledu sloaeene timorske strukture, koje su od susjednih potolina odvojene sistemima dubokih rasjeda koji zadiru u podlogu tercijarnih sedimenata. Zbog morfologije terena se duae pruaeanja —akovako-vinkovakog i Vukovarskog ravnjaka proteaee povr„inska i podzemna razvodnica koja istraaeivani prostor dijeli u dva sliva: Dravski na sjeveru i Savski na jugu. Cilj ovog rada bio je istraaeiti da li rasjedne zone izme﷿u ravnjaka i potolina predstavljaju nepropusnu granicu koja naslage dijeli u dva odvojena hidraulika sustava ili one ine jednu hidrauliku cjelinu. Analizom su obuhvaEe ne kvartarne naslage koje sadraee vodu pogodnu za vodoopskrbu, a koje zalijeaeu do dubine od 200 m. Rezultati analize pokazali su da litolo„ki kontinuitet vodonosnih slojeva duae rasjednih zona —akovako-vinkovakog i Vukovarskog ravnjaka nije prekinut, te da na razvodnici savskog i dravskog sliva ne postoji nepropusna hidraulika granica. Prostor istone Slavonije izme﷿u Drave i Save smatra se jed nim hidraulikim sustavom unutar kojeg postoje zone s razliitim vri jednostima transmisivnosti. Duae zona smanjene transmisivnosti hidraulike veze su oslabljene, ali nisu prekinute. Takve zone nisu prisutne samo duae rasjednih zona —akovako-vinkovakog i Vukovarskog ravnjaka nego i unutar pojedinih depresija. U sluaju da sniaeenje uzrokovano crpljenjem dosegne razvodnicu zapoinje dotok vode iz podruja s druge strane razvodnice, tj. razvodnica se premije„ta u odnosu na prirodni poloaeaj udaljavajuEi se od mjesta crpljenja.

Conceptual model for groundwater status and risk assessment - case study of the Zagreb aquifer system

This paper presents a conceptual model of the Zagreb aquifer system. The conceptual model can be applied to groundwater status risk assessment and pollution risk assessment at the local scale, thus satisfying both environmental and preventative/limitation objectives of the Water Framework Directive (WFD) and Groundwater Directive (GWD). Its main purpose is to apply a risk assessment procedure, according to the WFD requirements, and to serve as a foundation for setting up a numerical model of flow in both the saturated and unsaturated zones in order to identify pressure and impact effects on groundwater quality. The model is divided into two parts, taking into account the WFD requirement to assess a risk for a wide range of source-pathway-receptor relationships. The Global Conceptual Model (GCM) provides insight into the processes and pressures at the level of the groundwater system. It contains the geological and hydrogeological characterization of the Zagreb aquifer system and the description of the most significant point and diffuse sources and pathways of pollution and processes influencing pollutant behaviour in saturated and unsaturated zone of the groundwater system. The main pollutants of the Zagreb aquifer system are potentially toxic metals, nitrates, pesticides, pharmaceuticals and chlorinated aliphatics. A Local Conceptual Model (LCM) supports parameterization of the whole groundwater system through the description of heterogeneities and flow and solute parameters of the system components at two sites representing local conditions in the saturated (Stara Loza) and unsaturated (Kosnica) zones. This concept can be regarded as an effective tool for groundwater management of the groundwater system and its compartments and for communicating the conditions in complex groundwater systems with experts, policy makers and general public in an understandable way.

Statistical Indicators of Groundwater Geochemical Characteristics in a Quaternary Aquifer from the Mala Mlaka Well Field Catchment Area (Zagreb, Croatia)

High concentrations of sodium, potassium, nitrates and sulphates in the groundwater in the Mala Mlaka well field catchment area confirm the impact of agricultural activities on water chemistry. Analysis of time trends has shown that a decrease in inorganic components (nitrates and sulphates), which are sensitive to changes in oxidation/ reduction conditions in an aquifer, are caused by infiltration of oxygen- rich water rich in organic matter into the aquifers. Oxygen content reduction due to oxidation of the organic matter causes oxygen deprivation in the groundwater and consequently a reduction in nitrate and sulphate levels. An increase in chloride levels in the groundwater during 1994–2000 is a consequence of human activities in the catchment area. Multivariate statistical analyses, i.e. factor analysis, cluster analysis and multidimensional scaling (MDS) analysis have shown that the registered pollution sources in the catchment area, particularly illegal dump sites, cause degradation of the groundwater quality in some sites. This impact is detected over a distance of several hundred metres downstream from the registered pollution sources.

Hydrogeological characteristics of south hills, Ivanščica Mountain

ABSTRACT This article presents results of hydrogeological and hydrogeochemical research conducted at south hills, Ivanščica Mountain, situated in the northwestern part of the Republic of Croatia. Research was carried out in the summer 2013, between July and September. Hydrogeological mapping was undertaken on approximately 20 km2 (at a scale of 1:25000), with water samples taken from 10 springs. Rocks and deposits were classified into three hydrogeological units with respect to permeability. Two main aquifers were identified – the Triassic carbonate aquifer and the Badenian carbonate aquifer. The overall capacity of 41 registered springs (permanent and periodic) was estimated. According to their basic chemical composition, water from springs belong to Ca-HCO3 (calcium-hydrogen carbonate), CaMg-HCO3 (calcium magnesium-hydrogen carbonate) and to MgCa-HCO3 (magnesium calcium-hydrogen carbonate) types.