Delineating Groundwater Vulnerability and Protection Zone Mapping in Fractured Rock Masses: Focus on the DISCO Index

Helen Meerkhan,José Teixeira,Jorge Espinha Marques,Maria Afonso,Helder Chaminé

doi:10.3390/w8100462

Helen Meerkhan, José Teixeira + Show 3 more

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https://doi.org/10.3390/w8100462

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Abstract

Hard-rock catchments are considered to be source of valuable water resources for water supply to inhabitants and ecosystems. The present work aims to develop a groundwater vulnerability approach in the Caldas da Cavaca hydromineral system (Aguiar da Beira, Central Portugal) in order to improve the hydrogeological conceptual site model. Different types of information were overlaid, generating several thematic maps to achieve an integrated framework of key sectors in the study site. Thus, a multi-technical approach was used, encompassing field and laboratory techniques, whereby different types of data were collected from fields such as geology, hydrogeology, applied geomorphology and geophysics and hydrogeomechanics, with the fundamental aim of applying the so-called DISCO index method. All of these techniques were successfully performed and an intrinsic groundwater vulnerability to contamination assessment, based on the multicriteria methodology of GOD-S, DRASTIC-Fm, SINTACS, SI and DISCO indexes, was delineated. Geographic Information Systems (GIS) provided the basis on which to organize and integrate the databases and to produce all the thematic maps. This multi-technical approach highlights the importance of groundwater vulnerability to contamination mapping as a tool to support hydrogeological conceptualization, contributing to improving the decision-making process regarding water resources management and sustainability.

Highlights

Groundwater in fractured aquifers is considered an important source for irrigation, water supply, and industrial purposes [1]
This study was successfully undertaken through the combination of several major steps, where all the data collection techniques can be classified into two main categories (Figure 2) [21,22,26,47,48]: (i) mapping data: which include topography, remote sensing, morphotectonics, structural geology, land use and climatology; (ii) field and laboratory data: which comprise rock mass geotechnics, hydrogeological inventory, and hydrogeochemical and isotopic analysis
Vulnerability assessment mapping is an essential step in assessing intrinsic groundwater vulnerability to contamination and in delineating wellhead protection areas

Summary

Introduction

Groundwater in fractured aquifers is considered an important source for irrigation, water supply, and industrial purposes [1]. Water 2016, 8, 462 leakage of contaminants into groundwater, which in turn lead to the vulnerability of groundwater to contamination in varying degrees These factors include lithology, geostructure, topography, fracture network, slope, weathering grade, permeability, drainage pattern, climate and land use [6]. Extreme vulnerability is associated with a shallow water table, where fractures provide low contaminant decrease [9,10,11]. In this case, fractures increase vertical permeability, which affects the recharge rate and decreases the amount of contaminant attenuation. In fractured hydrosystems where groundwater flow is relatively easy and rapid, contamination may become widely dispersed [12,13]

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