Modeling of mixed karstic and alluvial recharge area for the drainage capture in Radovna River valley, Julian Alps (NW Slovenia)

In the Radovna River valley (NW Slovenia) in fluvioglacial sediments with high permeability and high yield, drainage capture supplies drinking water to over 20,000 inhabitants and extensive tourist facilities in one of the most important Slovenian tourist centers of Bled in the Gorenjska region. Drainage is dug at a depth of 10.0 m to 5.5 m and is 235 m long. It runs parallel to the river at a distance of 30 to 60 m. The total drainage flow ranges from 0.40 to 0.60 m³/s.

The Radovna River valley is a deep glacial valley with karstic plateaus on both sides of the valley. On the plateaus, sinkholes and smaller karst poljes are developed. The thickness of the fluvioglacial sediment in the valley exceeds 140 m. The position of the recharge area is such that it includes water infiltrating through the fluvioglacial sediment from the river and water infiltrating from the karst aquifer through the fluvioglacial sediment. The ratio of drainage water originating from the karst area and the river changes throughout the hydrological season. The proportion of water from the karstic plateau is higher in the high-water condition, and in the low-water conditions, water from the river bed is almost entirely dominant.

The paper presents a numerical model of groundwater flow toward the drainage, modeling both the inflow from the river area and the inflow from the karstic aquifer. The modeling is performed using the MODFLOW numerical model in the FREEWAT modeling environment.