engleski

The establishment of a teaching-research polygon in the area of Velika Gorica well field, Zagreb aquifer

Groundwater reserves of the Zagreb unconfined aquifer are defined as a strategic resource of groundwater in Croatia within the Croatian Waters’ Water Management Strategy. They present the only source of potable water for the inhabitants of the City of Zagreb and one part of the Zagreb County. In the past decades, groundwater level decline have been identified in the Zagreb aquifer (Nakić et al., 2013). Consequently, it became important to identify and quantify every single source of its recharge. The research presented within this abstract is focused on one part of the aquifer recharge i.e. the recharge which occurs from precipitation and infiltrates through the soil and the unsaturated zone into the aquifer (Ružičić et al., 2016). For the purpose of this research, a teaching-research polygon was constructed in order to observe and measure the process of precipitation infiltration through the soil and the unsaturated zone. Polygon is located in the southern part of the Zagreb aquifer, in the Eutric Cambisol on Holocene deposits (Bogunović et al., 1996), at the Velika Gorica well field. Teaching-research polygon is designed as a pedological pit with glass walls installed on two sides, enabling insight into the soil and unsaturated zone profile. Probes and suction cups are installed at different depths, with respect to defined pedological horizons. Probes measure moisture content, electrical conductivity and temperature, while suction cups are used to collect water that infiltrates into the unsaturated zone. Teaching-research polygon also has a weather station and pluviometer installed on the surface. Future monitoring will include measurement of major ion concentrations and stable isotope composition of water sampled from unsaturated zone, groundwater and precipitation. Ionic composition will be determined using ion chromatography while the water stable isotopes will be determined by laser absorption spectroscopy. By continuous measurement of selected parameters and frequent sampling of infiltrated water, it will be possible to quantify the value of effective infiltration and to determine the main geochemical processes that are occurring in the unsaturated zone. In order to better understand the water flow through the unsaturated zone, numerical simulation of water dynamics will be performed using HYDRUS-1D (Šimunek et al., 2008), while 2D and 3D images of moisture distribution will be obtained by using MoisturEC program (Terry et al., 2018).

unsaturated zone ; pedological pit ; effective infiltration ; Velika Gorica well field ; Zagreb aquifer

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