Modeliranje pretoka vode in prenosa za presojo vpliva geometrije podpovršinskih plasti na ranljivost alpskokraškega vodonosnika

Abstract

Karst areas are highly susceptible to contamination due to rapid recharge and throughflow caused by their heterogeneous structure with unknown networks of conduits embedded in a matrix of low conductivity. Vulnerability methods have been used to ensure adequate protection of drinking water resources. However, most of the studies assessing the vulnerability of karst aquifers consider it as a constant value in time and, therefore, under special hydrological conditions in space, which is an oversimplification of reality. In this work, the behaviour of an Alpine karst system characterised by rapid flow and transfer through vertical shafts has been studied by discrete numerical modelling using MODFLOW 6. Six numerical models have been designed with the aim of representing simple common geometrical configurations found in Alpine karst systems. These models simulate how the flow and transport response at the system outlet is influenced by the aquifer geometry and recharge conditions. The results confirm that the arrival of the tracer at the spring strongly depends on the conduit geometry and the recharge conditions. This demonstrates that karst aquifer vulnerability cannot be defined as a constant value but should be specifically assessed depending on the spatio-temporal conditions.Kraška območja so zelo dovzetna za onesnaženje zaradi hitrega napajanja in pretoka, kar omogoča njihova heterogena struktura z neznanimi omrežji kanalov, ki so del matrike z nizko prevodnostjo. Za zagotavljanje ustreznega varstva virov pitne vode so bile uporabljene metode proučevanja ranljivosti. Vendar večina študij, ki proučuje ranljivost kraških vodonosnikov, to obravnava kot časovno konstantno vrednost in kot prostor v posebnih hidroloških razmerah, kar je prevelika poenostavitev realnega stanja. V tem članku so bile z diskretnim numeričnim modeliranjem s programom MODFLOW 6 proučene lastnosti alpskokraškega sistema, za katerega je značilen hiter pretok vode po navpičnih jaških. Oblikovanih je bilo šest numeričnih modelov, katerih cilj je predstaviti preproste običajne geometrijske konfiguracije, ki jih najdemo v sistemih alpskega krasa. Ti modeli simulirajo, kako geometrija vodonosnika in značilnosti napajanja vplivajo na pretok in prenos na iztoku. Rezultati potrjujejo, da je prihod sledila v izvir močno odvisen od geometrije kanalov in značilnosti napajanja. To dokazuje, da ranljivosti kraških vodonosnikov ni mogoče opredeliti kot konstantno vrednost, temveč jo je treba proučevati specifično glede na prostorsko-časovne razmere