## 5 Discussion  
The steep gradient of the bedrock surface leads to rapid groundwater drainage, especially during periods of intense precipitation (Figure 9). This results in rapid hydraulic responses, manifested as a rapid increase in spring discharge and a rise in groundwater levels in the landslide body (Figure 2). Both precipitation and inflow from the carbonate hinterland depend on meteorological conditions, making the hydrogeological conditions in the landslide area, and consequently the stability of the landslide, sensitive to variations and seasonal changes in weather patterns. The third tracer test with uranine revealed slower groundwater flow (between 3 and 4 months), which was also indicated by isotope analysis, which estimated an MRT of 0.23 to 0.32 years [30]. The estimated groundwater storage capacity suggests that moisture levels remain elevated even during dry periods, potentially explaining delayed landslide responses to seasonal precipitation trends. Numerical modeling and large-/small-scale model experiments have demonstrated that transient groundwater flow during extreme weather events can create pressure differentials that exacerbate instability [40; 41; 42; 43]. Figure 9: Hydrogeological cross-section A-B with conceptual characteristic groundwater flow within the Urbas landslide (modified after [39]). The distinction between fast and slow groundwater flow is related to geological conditions. Slower groundwater flow is deeper and is likely to percolate up through the upper, weathered zone of the bedrock. The sliding surface is an additional element that can potentially influence groundwater flow patterns. The deeper flows, although slower, are important for the long-term storage of groundwater and the gradual release of water over longer periods of time. The stable temperature of the groundwater in the aquifer (Figure 2) that recharges the spring confirms this assumption. The groundwater temperature of 4 \({}^{\circ}\)C corresponds to the average air temperature in the Julian Alps at an altitude of approx. 1800 m [44], which is consistent with the results of isotopic analyses of previous studies [30], indicating that the water in the springs is recharged from higher altitudes with slower-flowing groundwater. The Urbas spring is a permanent spring with a stable discharge, which makes it an important source of drinking water. Its stability is ensured by the aquifer above the spring, which allows the temporary storage of groundwater and the recharge of the spring even under very dry conditions. The second salt tracer test confirmed the direct connection between the aquifer and the spring. With the pumping test carried out, we estimated the hydraulic conductivity of the aquifer to be 2.24 \(\times\) 10\({}^{-3}\) m/s. The stream drains the water from the spring Ui-1 over the landslide. Tracer tests showed that the stream also recharges the groundwater in the landslide body, which is discharged to the surface via the springs in the lower part of the landslide. This process was confirmed by the detection of the tracer in the PP-8 piezometer near the stream and in the springs Ui-7, Ui-6, and Ui-4. However, the stream also functions as a drainage pathway for groundwater in the lower part of the landslide, indicating that the Urbas spring is not the sole outlet for groundwater from the upper landslide recharge area. This was demonstrated in the first uranine tracer test, where the tracer injected at the top of the landslide was detected only in the stream at the lower part of the landslide. The Urbas landslide area is characterized by geological heterogeneity, which plays an important role in shaping groundwater flow patterns. The combination of highly permeable coarse-grained material and low-permeability clastic material creates a complex system of local aquifers, springs, and groundwater flow paths. This variability affects not only the rate and direction of groundwater movement but also the distribution of water throughout different sections of the landslide.