Geography Reference
In-Depth Information
In general, the status of groundwater contamination is determined by the
natural attenuation processes occurring within the zone between the pollution
source and the aquifer. Mainly two natural factors, i.e. physical processes and
chemical reactions occurring within the soil, unsaturated zone and saturated
zone are responsible for alteration in physical states and chemical forms of
contaminants, which ultimately leads to attenuation of contaminants. There
may be a single or multiple chemical reactions to work with other processes
resulting in a varying degree of attenuation.
These reactions depend on the specific soil and aquifer characteristics and
particular geochemical properties of each contaminant. Thus, groundwater
vulnerability is a function of geology and hydrogeology of the unsaturated and
saturated zones and physico-chemical properties of the contaminants.
All factors affecting groundwater vulnerability may vary from one place
to another. The groundwater vulnerability may be classified in two ways:
intrinsic vulnerability and specific vulnerability. The term ‗intrinsic
vulnerability' refers to the vulnerability of groundwater to contaminants
generated by anthropogenic or human activities taking into account the
inherent geological, hydrological and hydrogeological characteristics of an
area but being independent of the nature of the contaminants. On the other
side, term ‗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).
6.2. GIS-Based Methods to Evaluate Groundwater Vulnerability
Geographic Information System (GIS) technique has fundamentally
changed our thoughts and ways to manage natural resources in general and
water resources in particular (Jha et al., 2007).
GIS is designed to collect diverse spatial data to represent spatially
variable phenomena by applying a series of overlay analysis of data layers that
are in spatial register (Bonham-Carter, 1996). Vulnerability assessment is a
basis for initiating protective measures for important groundwater resources
and will normally be the first step in groundwater pollution assessment (Foster
et al., 2002). The GIS technique is of great significance in assessing the
pollution vulnerability of the aquifers over a large area.
