Groundwater Vulnerability and Delineation of Protection Zones in the Discharge Area of a Karstic Aquifer—Application in Agyia’s Karst System (Crete, Greece)

Abstract

This work represents a contribution to the protection techniques of karst aquifers against groundwater pollution. The paper sets out the methodology being introduced for the protection of the karstic system that gives rise to five (5) major groups of springs and supplies fourteen (14) pumping wells near Agyia Chania (Crete, Greece). Starting from a geological and hydrogeological survey of the area, the work presents a vulnerability assessment of the karstic aquifer based on the application of three index-based methods (EPIK, PRESK and DRISTPI). The protection zones for the discharge area of the aquifer were delineated through an integrated geomorphological approach and groundwater flow modeling. At first, the risk of polluting substances migration from ground surface to groundwater was considered based on the spatial distribution of vulnerability. Following this, the vulnerability was evaluated in the saturated zone, where the attenuation mechanisms of contaminants were reducing due to the raised flow velocity. The groundwater flow and contaminant transport processes was considered using the MODFLOW code. Next, the data from the vulnerability mapping and the groundwater flow simulation were merged into an integrated assessment to delimit the protection zones for the water abstraction points. The vulnerability assessment outlines zones of high vulnerability in the SE part of the area, far away from the discharge zone of the aquifer and the water abstraction points. These zones are associated with an intensive infiltration process via carbonate formations. Protection Zone I was delineated 20 m around the water abstraction points, and it should be excluded from any anthropogenic activity. Protection Zone II coves part of the very high and high vulnerability zones defined by the DRISTPI method (located upwards of the water abstraction points), as well as an area downwards of springs and wells, where the flow path lines which demonstrate the subsurface travelling time of 50 days are projected to the ground surface. Protection Zone III extends outside Zone Ι and Zone ΙΙ, up to the limits of the hydrogeological or hydrological basin, whichever is larger. It includes the entire capture zone (i.e., the surface and underground catchment area) that feeds the water abstraction points. In this manner the protection zones include the entire contributing area to water abstraction points, not just the ground surface recharge zone.

Optimizing the water-ecosystem-food nexus using nature-based solutions at the basin scale

“…Over the past two decades, the Koiliaris River watershed has undergone a comprehensive investigation (Kourgialas and Karatzas, 2011;Vozinaki et al, 2011;Sibetheros et al, 2013;Giannakis et al, 2014;Moraetis et al, 2015;Nerantzaki et al, 2015;Vozinaki et al, 2015;Morianou et al, 2017;Yu et al, 2019;Nerantzaki and Nikolaidis, 2020;Lilli et al, 2020a,b). The geological composition of the region, coupled with a significant fault running in a northeast-southwest direction, directs water movement toward the springs within the Koiliaris River Basin (Steiakakis, 2018;Steiakakis et al, 2023). The study area encompasses karst systems with a distinctive characteristic possessing unique hydraulic properties and transmissivities (Kourgialas et al, 2010).…”

The Risk of Contamination of the First Aquifer in the Central Part of the Świętokrzyskie Voivodship (Mhp-814 Piekoszów)

“…To plan appropriate actions for the protection of groundwater intakes, it is necessary to know the intrinsic vulnerability of the groundwater to contamination (Al-Mallah & Al-Qurnawi, 2018;Steiakakis, Vavadakis & Mourkakou, 2023). The intrinsic vulnerability determines the risk of migration of conservative contaminants from the ground surface to the first aquifer.…”