Critical zone studies in pre-alpine climate

Weighing monolith lysimeters enable precise measurement of water balance parameters, including infiltration, evapotranspiration, and deep percolation as well as studies of solute fluxes within the complex soil–plant–atmosphere continuum. At the experimental field of the Biotechnical Faculty, University of Ljubljana, two monolith lysimeters were installed to study solute transport and to measure evapotranspiration. In addition to the installed lysimeters, an advanced meteorological station is located at the same site, enabling measurement of other meteorological variables required for calculating evapotranspiration. To expand and establish a critical zone research site, the lysimeter station was equipped with two cosmic ray neutron sensors for proximity moisture sensing, as well as sampling points for drainage water and groundwater quality. The research center serves as a focal point for soil water balance studies in the peri-urban area of a pre-Alpine climate in central Slovenia, and is a part of SI-COSMOS network that spreads across the Continental, Alpine, Karst, Mediterranean, and Pannonian regions. Biotechnical faculty critical zone research field enables quantification of hydrological processes that control the upper critical zone water balance and contaminant transport under changing climate conditions. Evaluation after the first decade of operation shows that advances in weighing technology, lower boundary condition control, and data processing have made high-precision lysimeters very useful tools; however, they require intensive, regular maintenance to ensure data quality. Drainage water monitoring indicates favorable water quality conditions for developing circular water and nature based solutions in per-urban agricultural landscape.
Acknowledgements: This research was partially supported by ARIS research programme P4-0085, IC RRG-AG (IO-0022-0481-001), Interreg Alpine Space program, project Alpine Space Drought Prediction (A-DROP) (grant number 101147797), European Union – LIFE Programme (LIFE23-IPC-SI-LIFE4ADAPT), OPTAIN Horizon 2020 (grant number 862756), and the Slovenian CAP Strategic Plan 2023–2027 (grant number 33126-3/2025/23).