Kouli_etal_2008_Groundwater modelling_BOOK.pdf - Pantelis ...

GIS-Based Aquifer Modeling and Planning Using Integrated Geoenvironmental… 19
pollutant attenuation. Specific vulnerability is used to define the vulnerability of groundwater
to particular contaminants or a group of contaminants taking into account the contaminant
properties and their relationship with the various components of intrinsic vulnerability
(Doerfliger et al. 1999; Gogu and Dassargues 2000). Groundwater vulnerability to
contamination can be defined as the propensity or likelihood for contaminants to reach some
specific position in the groundwater system after their introduction at some point above the
top of the uppermost aquifer (Rao and Alley 1993). Vulnerability is usually considered as an
intrinsic property of a groundwater system that depends on its sensitivity to human and/or
natural impacts. Specific or integrated vulnerability, on the other hand, combines intrinsic
vulnerability with the risk of the groundwater being exposed to the loading of pollutants from
certain sources (Vrba and Zaporozec, 1994).
In general, the level of groundwater contamination is determined by the natural
attenuation processes occurring within the zone between the pollution source and the aquifer.
The concept of assessing groundwater vulnerability and contamination risk is based on an
origin-pathway-target model. Origin is the term used to describe the location of a potential
contaminant release. The pathway comprises the passage of contaminants from the origin to
the target, i.e. the water that shall be protected. Resource protection aims to protect the whole
aquifer; source protection aims to protect a spring or well. For resource protection, the
groundwater surface is defined as the target, and the pathway consists of the unsaturated zone.
For source protection, the pathway additionally includes the flow in the aquifer towards the
spring or well (Goldscheider 2004). From a quantitative point of view, three aspects are
important for vulnerability assessment: the travel time of a contaminant from the origin to the
target, the attenuation along its pathway, and the duration of a contamination at the target
(Brouyère 2004). This approach makes it possible to validate vulnerability assessments by
means of artificial tracer tests, and chemical and microbiological groundwater quality data
(Goldscheider et al. 2001; Holman et al. 2005; Perrin et al. 2004).
Groundwater vulnerability mapping is based on the idea that some land areas are more
vulnerable to groundwater contamination than others (Piscopo 2001) and, since the 1980s,
basic vulnerability indices have been developed extensively for planning purposes in many
areas of the world (e.g. Carter et al. 1987; NRA 1994). Planning is often based on concepts of
both resource and source protection, although the success of EPA in U.S. or EU and national
government policies on groundwater protection have often been brought into question since
general policies often require significant local modification and improved dissemination of
information (e.g. Foster and Ilbery 1992; Foster and Thorn 1993). The vulnerability concept
is implemented by classifying a geographical area with regard to its susceptibility to
groundwater contamination rather than using dynamic groundwater models, because
groundwater models often require data which is unavailable in many parts of the world (Knox
et al. 1993).
The present chapter highlights geographic information system (GIS) and remote sensing
(RS) technologies and presents a state of the art review on the application of these two
emerging techniques coupled with geochemical and geophysical approaches in a river basin
in Greece for groundwater modeling/management and planning.