Hydrogeochemical Characterization of a Warm Spring System in a Carbonate Mountain Range of the Eastern Julian Alps, Slovenia

Abstract

The Alps represent an area where many deep groundwater circulations occur as thermal springs. In the Bled case study, the thermal water temperature, at it is discharged to the surface, is between 19–23 °C. In order to determine the extent (e.g., geometry) and the origin of the pronounced deep circulation system in the Bled area, chemical and isotopic measurements of waters from different hydrogeological systems were performed (e.g., surface water, thermal water, fresh groundwater). Hydrogeochemical methods were used to tie together the above-mentioned parameters. The results have shown that thermal outflow in Bled is determined by the presence of a deep-water circulation system, where the dissolution of carbonates minerals is the main hydrogeochemical process affecting chemical components of natural water flow. The correlation of the major ions suggests that the recharge area is represented by both limestone and dolomite rocks. Moreover, the results of δ18O and δ2H of all samples indicate that the recharge is mainly meteoric precipitation. The recharge altitude was estimated for two sampled fresh groundwater springs. The isotopic compositions of those two springs suggest the range from δ18O = −8.68‰, δ2H = −57.4‰ at an elevation of 629 m to δ18O = −9.30‰, δ2H = −60.1‰ at an elevation of 1216 m. The isotopic analysis has confirmed that the thermal water recharges from altitudes of 1282–1620 m a.s.l.

Using stable isotopes and major ions to identify recharge characteristics of the Alpine groundwater-flow dominated Triglavska Bistrica River

“…It was estimated that the altitude effect in precipitation is -0.8‰ δ 18 O/km. This value is in good agreement with the estimated altitude effect based on spring water δ 18 O values (-1.1 ‰ δ 18 O/km) in the Radovna River valley in NW Slovenia (Torkar et al, 2016) and (-1 ‰ δ 18 O/ km) in Lake Bled and surroundings (Serianz et al, 2020b).…”

“…These studies suggest that the water of the alpine springs is dominated by HCO 3 -, Ca 2+ and Mg 2+ ions and that most of the springs were near equilibrium in terms of calcite. These results can be confirmed by recent hydrogeochemical studies in similar environments (Mezga, 2014;Torkar et al, 2016;Serianz et al, 2020b).…”

Application of Airborne LiDAR Data to the Archaeology of Agrarian Land Use: The Case Study of the Early Medieval Microregion of Bled (Slovenia)

“…Nevertheless, there are small patches of hydromorphic soils (Alluvial soils, Hypogley, Amphigley) with high FC (FC index 4; mSWI: 0, −5). Their formation was possible due the glacial activity and postglacial fluvial processes, which have resulted in deposition of clayed sediments north of the Bled lake [92]. The brown soils in the Zone 3 are the most suitable soils for modern agriculture in the area [94], providing that drought effect can be mitigated (for example, by irrigation or drought-resistant crops).…”

“…A characteristic feature of the Bled landform is the frontal moraine on the northeast edge of the lake and the dome-shaped monadnocks rising above the general level of glacial deposits [90][91][92]. Bled Castle is located on one such cliff-like dome-shaped monadnocks [93].…”

“…Bled microregion (decimal longitude and latitude coordinates of the map centre: 14.1139; 46.3752), geological background. The most main geological units prevailing in the study area are presented (source data adopted from[90][91][92]; North at the top).…”