Autor: Laura Bačani, mag. ing. geol.
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 declines have been identified in the Zagreb aquifer. Consequently, it became important to identify and quantify every single source of its recharge. In order to observe and measure the processes in the unsaturated zone a teaching-research polygon was constructed (Figure 1) in collaboration between Velika Gorica water supply system (VGV) and Faculty of Mining, Geology and Petroleum Engineering (RGNF), University of Zagreb. Polygon is constructed in 2018. and is located in the southern part of the Zagreb aquifer, at the Velika Gorica well field. The research polygon is designed in order to be suitable for scientific research and educational purposes. The construction design of the pedological pit was prepared by the company HIDROPROJEKT-ING d.o.o. from Zagreb in cooperation with Velika Gorica water supply system and the Faculty of Mining, Geology and Petroleum Engineering, University of Zagreb.
Figure 1. Teaching-research polygon (pedological pit and meteorological station).
The research polygon (Figure 1) is consisted of pedological pit which is 3.25 m deep and has external floor dimensions of 3.4 × 3.4 m (internal dimensions 3 × 3 × 3 m). Glass walls (Figure 2) were installed in the two opposite side walls of the pit (east and west), which enable visual inspection of the unsaturated zone profile and the installation of measuring devices.
Figure 2. Movable glass walls which enables visual inspection of the unsaturated zone profile and the installation of measuring devices
Measuring devices installed in the eastern wall of the pit are TRIME PICO 64 probes (Figure 3a) which measure moisture content, electrical conductivity and temperature, and Suction Cups (Figure 3b) which collect water samples for chemical and isotopic composition analysis. Measured data are stored at data loggers IMKO globeLog (Figure 3c) and dataTaker DT80 (Figure 3d) which are also located inside the pit. The meteorological station Davis Vantage Pro2 (Figure 3e) is installed at the surface, next to the pedological pit at the elevation of 2,5 m. The station measures precipitation, solar radiation, humidity, wind strength and direction and air temperature. The measured data from the station is also stored on data loggers. The installation of devices at the research site was completed in early 2019, and from February 1, 2019. the measurements are continuously collecting data of electrical conductivity, temperature and moisture content and the amount of precipitation, solar radiation, humidity, wind strength and direction and air temperature. The collection of water samples for chemical and isotopic analyses is carried out on a monthly basis.
Figure 3. Measuring devices on scientific-research polygon: a) TRIME PICO 64 probes, b) Suction Cups, c) globeLog loger, d) dataTaker DT80, e) meteorological station
The main purpose of this scientific - research project is to monitor the precipitation infiltration process in the unsaturated zone until it reaches the water table, and to identify hydraulic parameters and geochemical processes in the unsaturated zone. The research will enable detail quantification of amount and intensity rate of precipitation, and also the precipitation infiltration in the unsaturated zone and aquifer. The research will improve the knowledge about aquifer boundaries and parameters, which will further upgrade the regional groundwater models as well as the unsaturated flow models through the Zagreb aquifer.
The scientific contribution of this research is the quantification of the amount of precipitation infiltration in the Zagreb aquifer area, i.e. area of Velika Gorica wellfield and definition of precipitation intensity and duration contribution to water seepage through the unsaturated zone. A great contribution will be visible in the implementation of isotopic methods in hydrogeological studies. Also, the improvement of regional groundwater flow models is expected, the possibility of identifying the climate change impact on the aquifer recharge system in form of precipitation infiltration, as well as greater competitiveness of the faculty hydrogeological research group, which will be manifested through the acquisition of new knowledge and experience in the unsaturated zone research. In addition, the establishment of a research site will enable the development of new research, primarily related to pollution migration from the surface to the groundwater of the Zagreb aquifer. This research will enable further profiling of RGNF as a reference scientific institution at the University of Zagreb, but also throughout the Republic of Croatia, which conducts competitive scientific research in hydrogeology, as one of the basic scientific disciplines that contributes to sustainable management and protection of water resources. The research polygon will be used for scientific research, but also for teaching purposes in certain graduate studies of RGNF, which will result in greater competitiveness of our students in the world.
Brochure link: https://moodle.srce.hr/eportfolio/view/view.php?id=109547
Project manager: Prof. dr. sc. Kristijan Posavec, RGNF
Laura Bačani, mag.ing.geol. is a research assistant at the Department of Geology and Geological Engineering at the Faculty of Mining, Geology and Petroleum Engineering, University of Zagreb. She enrolled in the PhD study program of Applied Geosciences, Mining and Petroleum Engineering on 23.10.2018. with a topic entitled Defining the hydraulic parameters of the unsaturated zone in order to determine the amount of Zagreb aquifers recharge in the area of the regional water supply system Velika Gorica.
Google Scholar https://scholar.google.com/citations?hl=hr&user=J2LRHAIAAAAJ