Hydrogeological investigation of landslides Urbas and Čikla above the settlement of Koroška Bela (NW Slovenia)

The area above the settlement of Koroška Bela is highly prone to slope mass movements and poses a high risk for the safety of the settlement. To get an insight into the hydrogeological conditions and processes which can affect mass movements in this area, hydrogeological investigations, including hydrogeological mapping, discharge measurements of springs, performance of infitrometer and slug tests were performed. The results of these investigations show complex and heterogeneous hydrogeological conditions, predisposed by geological and tectonic setting and active mass movements which cannot be uniformly described. Observed large flctuations in the rate of discharge of springs and groundwater level in observation wells are highly dependent on meteorological conditions. Estimated hydraulic conductivity of the soil is relatively high (2×10 -4 m/s) and reflcts the loose structure and high content of organic matter in the upper part of the forest soil. Hydraulic conductivity of more permeable sections of boreholes is in general higher in the upper parts, in predominantly gravel layers (in range from 2×10 -3 to 1×10 -5 m/s), than in the deeper clayey gravel parts (3×10 -5 to 1×10 -7 m/s). In the area of the Čikla landslide the average hydraulic conductivity is estimated at 8.99×10 -4 m/s and is higher than in the area of the Urbas landslide (3.05×10 -4 m/s)

Skrb za pitno vodo

Safeguarding Drinking WaterLjubljana's water resources lie in the immediate vicinity of built-up urban areas or even below them. For decades, they have been safeguarded as water-protection areas, which are specified by implementing regulations. However, formal protection through regulations is insufficient if the goal is to manage these sources in a sustainable manner. One of the most important goals of sustainable management is maintaining suitable provision of fresh drinking water without using any technological procedures toVodni viri mesta Ljubljane so v neposredni bližini pozidanih mestnih zemljišč ali celo pod njimi. Že desetletja jih varujejo vodovarstvena območja. Eden od najpomembnejših ciljev trajnostnega upravljanja je ohranjanje ustrezne oskrbe z naravno pitno vodo brez tehnoloških postopkov njene priprave, kar Ljubljančani uvrščajo visoko na lestvici vrednot življenja v glavnem mestu Slovenije. Upravljanje ogroženih vodnih virov v urbanih okoljih zahteva celosten pristop in stalne aktivnosti. S pomočjo računalniških orodij znamo sisteme simulirati in tako pridobiti dodatna védenja o njihovem delovanju. Ta so v pomoč pri dolgoročnih odločitvah ali na primer ob okoljskih nesrečah. Za ustrezno načrtovanje so potrebna strokovna orodja, ki omogočajo zanesljive, pregledne in kvantitativne ocene učinkov ukrepov. Razpolaganje z zanesljivimi ocenami stanja in napovedmi olajšuje delo odločevalcem in tudi komunikacijo med deležniki. Povezava v monografiji predstavljenih postopkov in rezultatov v sistem izvedljivega upravljanja z vodnimi viri v Ljubljani je dosežek, ki je lahko zgled številnim podobnim okoljem, ne le v Sloveniji, ampak tudi širše

Modelling heterogeneity of Ljubljana polje aquifer using Markov chain and geostatistics

Heterogeneity of the aquifers is one of the key factors that control transport processes in groundwater. It is defined by the spatial distribution of hydofacies-sedimentsformed in characteristic depositional environments and have typical hydrogeological properties. Due to the (in time and space) changing sedimetological conditions, is the distribution of hydrofacies in nature often complex and difficulttodefine.The difficulty of this procedure most of ten limits reliability and consequently applicability of numerical transport models. For the purposes of improvement of reliability of hydrological modelling in the area of alluvial deposits of Ljubljana polje a hydrogeological model was constructed. It is based on the borehole logs, supplemented with geological conceptual information and geostatistical methods, combined with Markov chain models. The model consists of four units - hydrofacies with different volume tricportions (Gravel 45 %, Silt and clay with gravel 36 %, Silt and clay 5 % and Conglomerate 14 %). The used approach enables development of a set of equally probable realisations of spatial distribution of hydrofacies that are conditioned to the borehole data and represent geologically plausible image of the heterogeneity of the aquifer

Evaluation of water resource exploitation options using the MIKE SHE integrated hydrogeological modelling package – case study Selniška Dobrava

Based on the results of long-term research, Selni{ka Dobrava water resource was estimated as an adequate source of drinking water supply for the Maribor waterworks.Further activation of the resource for its optimum exploitation and management requires the determination of suitable pumping well locations on the basis of hydrogeological properties. This paper describes the development and application of an integrated hydrogeological model for the Selniška Dobrava. Model development is considered to be an important part in the establishment of sustainable water management policies for the Selniška Dobrava- Maribor waterworks. Selni{ka Dobrava model was developed by usingthe MIKE SHE integrated modelling package. The model enables an analysis of the complex hydrogeological regime in the region and the prediction of environmental impacts of various management options. Different scenario simulations were used to evaluate pumping station location suitability and the possibility of pumping sufficient quantities of water. Results of different simulations show that the construction of a pumping station for 200 l/s and more on Selniška Dobrava is possible. The model indicates a more favourablesetting up of pumping wells in the section transversal to groundwater flow direction. Such setting up enables an easier application of water resource protection measures

The Impact of Ljubljana’s Waste Deposit »Barje« on Groundwater

Ljubljana’s waste deposit is situated on rather thick formation of quaternary sediments on the northern margin of Ljubljansko Barje (Ljubljana Moor). The upper part of quaternary sediments consists of high compressive silty and clayey layers till the depth of aprox. 33 m. These layers are very heterogeneous and one can only find one continuous clayey gravel layer among them at the depth of 8 m and 4 m thick. Below these layers there is the Upper gravel aquifer and from the depth of 72 m there is the Lower gravel aquifer. The bottom of quaternary sediments is aprox. at 140 m depth. The consolidationof highly compressive upper layers and organic compounds from landfill leachate produce the evident impact by reducing conditions in the geological layers below the waste deposit.Though we can detect the reducing conditions also from natural environment in confined layers and rich organic matter content and also from other sources of contamination in the highly urbanized environment. The geometry of the contamination plume was notinvestigated in detail and also not the redox process dynamics. The advection velocities and actual contamination of groundwater are rather low. Further protection measurements will be designed by the aid of the established monitoring results

Characterizing the groundwater flow regime in a landslide recharge area using stable isotopes: a case study of the Urbas landslide area in NW Slovenia

Slope stability strongly depends on the prevailing hydrological and hydrogeological conditions. The amount and intensity of precipitation and changing groundwater levels are important landslide triggering factors. Environmental tracers, including the chemical and stable isotope compositions of precipitation and groundwater, were used to gain insight into the groundwater dynamics of the Urbas landslide. The landslide is situated in a mountainous area with steep slopes and high precipitation amount and poses a high risk for the safety of the Koroška Bela settlement that lies downstream. The stable isotope analyses of oxygen-18 (18O) and deuterium (2H) in the precipitation and groundwater were used to estimate the groundwater mean residence time and the average altitude of the landslide recharge area. This information will help to plan and prioritize remedial landslide measures aiming to reduce the recharge of the landslide body and, thus, lower the risk of transformation of the sliding material into debris flow. The results of the chemical analysis of samples taken from springs and a piezometer show a Ca–HCO3 water type. This indicates low water–rock interaction in a landslide area composed of Upper Carboniferous and Permian clastic rocks and points to upper laying carbonate rocks and scree deposits as the main recharge area. Water samples for stable isotope analyses of δ18O and δ2H were collected from a rain gauge, springs, and a piezometer over a two-year period (2018–2020). The estimated mean recharge altitude of the groundwater at sampling points was from approximately 1700 to 1800 m a.s.l. with a mean residence time of 2–5 months

Risk assessment for open loop geothermal systems, in relation to groundwater chemical composition (Ljubljana pilot area, Slovenia)

Shallow geothermal energy is a renewable source of energy that can be used effectively with open loop geothermal systems. Knowledge of hydrogeological conditions is a prerequisite for the successful implementation and operation of such systems. The article describes a risk assessment of open loop geothermal system operation related to the chemical composition of groundwater in the area of the City of Ljubljana. Results of the study show that in the area of the Ljubljansko polje aquifer, the geochemical characteristics of the groundwater do not represent a risk of possible operational problems for an open loop geothermal system. On the contrary, the chemical composition of the groundwater in the Ljubljansko barje aquifer indicates a risk of corrosion and/or the precipitation of minerals, which can lead to diminished efficiency of the geothermal system or even damage that can result in the interruption of operations. In order to avoid operational problems in open loop systems, wells must be a professionally designed and installed, and groundwater geochemical characteristics properly determined. In the latter, it is important to take into account the method of sampling, since the chemical composition of water in the aquifer and in the geothermal system may vary significantly

Impact of Open-Loop Systems on Groundwater Temperature in NE Slovenia

To achieve sustainable and efficient use of shallow geothermal resources, it is important to understand the heat transfer in the subsurface of the planned geothermal system. In the City Municipality of Murska Sobota, NE Slovenia, the use of geothermal open-loop systems has increased in recent years. Their high spatial density raises the question of possible mutual interference between the systems. By compiling geological, hydrogeological, and thermal data, obtained from the monitoring network, fieldwork, and knowledge of regional hydrogeological conditions, we have developed a transient groundwater flow and heat transfer model to evaluate the impact of the open-loop systems on the subsurface and surrounding systems. The transient simulation showed that the thermal state in the observed area is restored over the summer, when the systems are not in operation. Also, the systems do not have significant mutual interference that would affect their efficiency. However, as interest in installing new systems in the area increases, simulations of the thermal plumes of new geothermal systems are needed to ensure sustainable and efficient use of shallow geothermal energy in the future