To confirm or update the actual conceptual model of the Iška alluvial fan aquifer, three pumping tests were conducted in September 2018. It was performed in three deep wells: VD Brest-1a, VD Brest-2a and VD Brest-4a, extending into the lower layers of the Pleistocene alluvial deposits. Drawdown in groundwater level at nearby piezometers were recorded during pumping. After the pumping tests were carried out, followed cabinet work, which in the first phase consisted of editing the data taken in the field and the first plotting of the reduction curves as a function of time - s (log t). For ease of further processing, the curves were divided into three phases, namely the first, second and third phases. The second phase was first used to calculate the hydraulic parameters of the aquifer. They were determined based on Theis method with Jacob corrections for each pumping test individually and finally united to average. Hydraulic permeability (K) for the whole aquifer is 4.35⠙10-4 m/s. Storativity was not calculated for the entire aquifer but only for individual wells due to the large range of results. The third phase determined the part of the curve when the cone of depression reaches edge of the aquifer, which is reflected in the fluctuation of groundwater levels. The disorder is noticeable in all wells and is not locally conditioned. Extension velocity drops, when cone of depression reaches layers with different hydraulic parameters. Fluctuations of groundwater level could be affected by the Iška river and rain precipitation, but due to the sinking nature of the Iška river and insufficient data, the idea could not be confirmed. Consequently, a precise interpretation of the pumping tests was ultimately not possible. As previously known, aquifer of Iška alluvial fan is not limited by the impermeable boundary, so fluctuations are expected at the terminal end of the pump test.
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