The groundwater dynamics of the aquifer system at Iška fan

Leta 1981 je bila v sistem javne oskrbe s pitno vodo vključena vodarna Brest, ki zajema podzemno vodo Iškega vršaja na različnih globinah. Onesnaženja podzemne vode s pesticidi in drugimi onesnaževali so vodila k spremembi režima črpanja in sicer tako, da so daljša obdobja pretežno delovali plitvi vodnjaka, ob problemih glede količin ali kakovosti v plitvih vodnjakih, pa je bil poudarek na črpanju iz globokih vodnjakov. Leta 2009 je bil izveden enomesečni črpalni poskus na VD Brest 1a z namenom, da se ugotovi dinamika podzemne vode pri različnih kombinacijah delovanja plitvih in globokih vodnjakov. Na osnovi zbranih podatkov so bili narejeni izračuni parametrov vodonosnika, kot so transmisivnost, koeficient elastičnega uskladiščenja, izgube v vodonosniku in spremembe gradientov podzemne vode. Izračuni in spremembe fizikalno-kemijskih parametrov v obdobju črpalnega poskusa zavračajo konceptualni model vodonosnikov Ljubljanskega barja, po katerem sta spodnji in zgornji pleistocenski vodonosnik med seboj ločena z glinasto plastjo in med njima ni hidravlične povezave. Analiza podatkov je pokazala, da vodonosniki na območju Iškega vršaja zelo hitro odreagirajo tako na ekstremne vremenske razmere, kakor tudi na človekove posege. Črpanje iz različnih vodonosnikov vpliva na spremembe gradientov, kar ima za posledico prenos onesnaževal iz zgornjih holocenskih plasti v spodaj ležeče pleistocenske vodonosne plasti. Nižanje koncentracij DAT v VD Brest 9 je posledica spremembe gradienta v smeri vodnjaka VD Brest 1a in kaže na hidrodinamično povezavo med holocenskim, zgornje pleistocenskim in spodnje pleistocenskim vodonosnikom.The water field Brest is in production since 1981, from where groundwater is abstracted from different depths through a series of 10 shallow wells. Pesticides and other contaminants present in the groundwater caused a change in the pumping regime. In the 2009 a pumping test was performed. Groundwater was abstracted for one month with the aim to define the groundwater dynamics with the combination of different pumping regimes from shallow and deep wells. Based on the measured data some of the aquifer parameters were calculated, such as transmissivity, the coefficient of storage and groundwater gradient changes. The calculations and changes of physical-chemical parameters of groundwater in the time of the pumping test reject the conceptual model of the Ljubljansko barje aquifers because the upper and lower Pleistocene aquifers are separated by a layer of clay and there is no hydraulic connectivity between them. The data analysis confirms that the aquifers of Iška fan are very sensitive to extreme weather conditions as well as to human impacts. The groundwater abstraction from different aquifers influences the groundwater gradient which can cause the pollutant transport from the upper Holocene aquifer to the underlying Pleistocene upper and lower aquifers. Lower DAT concentrations in the shallow well VD Brest 9 is a consequence of groundwater gradient change in the direction towards well VD Brest 1 and indicates to the hydrodynamic connection between the Holocene, the upper Pleistocene and the lower Pleistocene aquifer

Springs on Ljubljana polje and Barje area, significant for quantity and quality condition of the groundwater body (Slovenia)

The intergranular aquifer of Ljubljana Field and the aquifer system of Ljubljana Moor are the most important sources of drinking water for Ljubljana.The springs that appear on the area of both groundwater bodies reflect the groundwater status, quantity and quality. The spring water in the Ljubljana Field appears on vowel change of the gravel terrace. We follow them in the lower part of Ljubljana Field aquiferfrom Fu‘ine to confluence of rivers Sava and Ljubljanica. The spring water directly indicates the condition of groundwater level and the quality.On the Ljubljana Barje there are important springs on the southern edge. These springs are crucial observation point for the quality and quantity status monitoring of the inflow fro main recharge area of Ljubljana Moor aquifers that are exploited for the water supplysystem. By the detailed analysis of older sporadic measurements of springs in Ljubljana Polje and Ljubljansko barje we were able to assess the changes in theirs trends of quantity and to design the monitoring network of springs that would acquire adequate data for the actual and future assessment of quantity an quality of these groundwater bodies in the frame of all other available and representative observation points

Adaptation of water supply to changing climate and land-use activities, case of Ljubljana water supply, Slovenia

A risk management methodology is presented for the adaptation of water supply to changing climate and land-use activities, considering socio-economic aspects. Several management options were selected for the case of the public water supply of Ljubljana, the capital of Slovenia. The major management actions for improving drinking water safety are (1) land-use limitations within the drinking water protection areas and (2) drinking water treatment. Trends in groundwater level are decreasing, above all in the area of well fieldstherefore, artificial recharge and setting up a new independent well field were also considered. The management actions were evaluated according to several criteria, such as water supply risk reduction for the various users (drinking, agricultural, and industrial) and realization of the actions (cost, flexibility, and leg time). For management options, the ranking “Fuzzy Decimaker” tool was applied, which is based on a Multiple Criterion Decision Making (MCDM) technique. Ranking of management actions has shown that all management actions are good as they are clustering in the corner close to the ideal value. For a particular well field, farming limitations in the drinking water protection areas are the best and water treatment is the worst management action, which is due to high costs, low flexibility, and longer lag time

Impact of land use changes on flood risk and water supply

V članku bo prikazan vpliv spremembe rabe zemljišč zaradi naravnih ali antropogenih dejavnikov na površinski odtok in stanje podzemnih voda, s tem pa na poplavno nevarnost, ter vpliv na znižanje podzemne vode ob vodnjakih in s tem na (ne)varno delovanje vodooskrbnega sistema. Vplivi spreminjanja rabe zemljišč in gozdne zarasti na vodozbirnem območju na poplavno nevarnost ob reki Iški in vodarni Brest ter povezave med površinskimi in podzemnimi vodami ob visokih vodah in v sušnem obdobju, od katerih je odvisno delovanje vodarne, ki oskrbuje Ig in Ljubljano z vodo, so bili analizirani s povezovanjem hidrološkega, hidravličnega in hidrogeološkega modeliranja. Obravnavali smo 27 scenarijev, ki poleg sprememb rabe zemljišč vključujejo tudi različne padavinske dogodke, vplive podnebnih sprememb ter naravnih nevarnosti (žled, lubadar) in človekove posege v gozd (pogozdovanje). Prikazani so spremembe poplavne nevarnosti za poselitev na Iškem vršaju in neugodni vplivi na oskrbo z vodo iz vodarne Brest. Posledice naravnih ali antropogenih sprememb rabe tal je z omilitvenimi ukrepi mogoče vsaj delno omejiti, opozoriti pa velja, da na območjih s pravnim režimom veljajo omejitve, prepovedi in zapovedi, ki vplivajo tudi na sanacijske ukrepe. Zato je treba slediti poti vode in v posameznih procesih ovrednotiti vir in stopnjo nevarnosti pri običajnih razmerah in ob izrednih dogodkih.This article describes the impact of land use changes within the Iška River catchment, due to natural or anthropogenic factors, on surface runoff and groundwater status, and consequently on flood risk along the Iška River. Additionally, the impact on the lowering of groundwater level around the water supply facility Brest and its wells, and thus on the functioning of the water supply system, supplying drinking water to Ig and Ljubljana, is presented. The impact of changes in land use and forest overgrowth within the catchment on flood risk and on the connections between surface water and groundwater, which enable the functioning of the water supply facility Brest, were analysed by a combination of hydrological, hydraulic and hydrogeological modelling. Twentyseven scenarios were examined, which, in addition to land use changes, included different precipitation events, climate change scenarios, natural hazards (ice storms, bark beetles), and human interventions (afforestation). The consequences of natural or anthropogenic land use changes can be limited, to some extent, by mitigation measures. However, it should be noted that in the areas protected by the legal regime, restrictions, prohibitions and rules apply that also affect remedial measures. Therefore, the water flow must be followed. For the individual processes, the source and the level of risk under normal and emergency conditions must be evaluated

Daily Fluctuations in the Isotope and Elemental Composition of Tap Water in Ljubljana, Slovenia

The isotope and elemental composition of tap water reflects its multiple distinct inputs and provides a link between infrastructure and the environment over a range of scales. For example, on a local scale, they can be helpful in understanding the geological, hydrogeological, and hydrological conditions and monitor the proper functioning of the water supply system (WSS). However, despite this, studies examining the urban water system remain limited. This study sought to address this knowledge gap by performing a 24 h multiparameter analysis of tap water extracted from a region where the mixing of groundwater between two recharge areas occurs. This work included measurements of temperature and electrical conductivity, as well as pH, δ2H, δ18O, d, δ13CDIC, and 87Sr/86Sr ratios and major and trace elements at hourly intervals over a 24 h period. Although the data show only slight variations in the measured parameters, four groups were distinguishable using visual grouping, and multivariate analysis (Spearman correlation coefficient analysis, hierarchical cluster analysis, and principal components analysis). Finally, changes in the mixing ratios of the two sources were estimated using a linear mixing model. The results confirm that the relative contribution from each source varied considerably over 24 h

Synthesis of past isotope hydrology investigations in the area of Ljubljana, Slovenia

Water isotope investigations are a powerful tool in water resources research as well as in understanding the impact that humans have on the water cycle. This paper reviews past hydrological investigations of the Ljubljansko polje and Ljubljansko barje aquifers that supply drinking water to the City of Ljubljana, with an emphasis on hydrogen, oxygen and carbon stable isotope ratios. Information about the methods used and results obtained are summarised, and the knowledge gaps identified. Overall, we identified 102 records published between 1976 and 2019. Among them, 41 reported stable isotope data of groundwater, surface water and precipitation and were further analysed. Isotope investigations of the Ljubljansko barje began in 1976, while groundwater and surface water investigations of the Ljubljansko polje and along the Sava River began as late as 1997. Isotope investigations of carbon started even later in 2003 in the Ljubljansko polje and in 2010 in the Ljubljansko barje. These investigations were performed predominantly in the frame of short-term groundwater research projects at five main wellfields and sites along the Sava River. Almost no large-scale, long-term stable isotope studies have been conducted. The exceptions include groundwater monitoring by the Union Brewery in Ljubljana (2003- 2014) and precipitation in Ljubljana since 1981. Since 2011, more detailed surveys of the Ljubljansko barje were performed, and in 2018, the first extensive investigation started at wellfields and objects that form part of the domestic water supply system. Given the number of available studies, we felt that publishing all the numerical data and appropriate metadata would allow for a better understanding of the short and long-term dynamics of water circulation in the urban environment. In the future, systematic long-term approaches, including the appropriate use of isotopic techniques, are needed

Isotopic characterisation of surface water from the Sava and Iška rivers, Slovenia, during the 2020-2021 sampling campaign

The two datasets include monthly hydrogen (δ²H) and oxygen (δ¹⁸O) sampling data for (i) surface water from the Sava and Iška rivers and (ii) groundwater from the Ljubljansko polje (LP) and Ljubljansko barje (LB) aquifers, the primary sources of drinking water for the City of Ljubljana. Sampling was performed between January 2020 to December 2021. The Sava River sampling was performed at Sava Brod and Sava Šentjakob, while the Iška River samples were collected at Iška vas. Besides isotope data, physico-chemical parameters (water temperature and electrical conductivity) were measured on-site at each location. In addition, water discharge and temperature data were obtained from the Slovenian Environment Agency. Altogether, 56 samples of surface water were collected. Groundwater samples were collected from the Kleče, Hrastje, Jarški prod, Šentvid wellfields (LP), and the Brest wellfield (LB). Groundwater sampling was performed at 13 preselected wells from all five wellfields. If the selected well was not operating, the closest well was sampled instead. Overall, 29 different wells were sampled, and 295 samples were collected. In-situ, temperature measurements were also recorded. The obtained isotopic data provide information on the temporal and spatial variability of surface water and groundwater in the Ljubljana basin