Geography Reference
In-Depth Information
The method could not get wide popularity, although its performance has
been assessed by applying it in GIS platform in some recent past studies
(Debernardi et al., 2008; Polemio et al., 2009; Kazakis and Voudouris, 2011).
6.3.4. AVI Rating System
In this method, two physical parameters are considered: the thickness of
every sedimentary unit above the uppermost, saturated aquifer surface (d) and
the estimated hydraulic conductivity of each of these sedimentary layers (k).
Firstly, hydraulic resistance (c) is calculated by the following equation
(Stempvoort et al., 1992):
n
d
c
i
k
i
1
(26)
i
where, n = number of sedimentary units above the aquifer; d = thickness of
each sedimentary unit above the uppermost aquifer, and k = estimated
hydraulic conductivity of each sedimentary unit. The parameter c is defined as
a theoretical factor used to describe the resistance of an aquitard to vertical
flow (e.g. Kruseman and de Ridder, 1990).
The hydraulic resistance (c) has dimension of time, which indicates the
approximate travel time for water to move by advection downward through the
various porous media above the uppermost saturated aquifer surface.
However, it should be noted that, in a strict sense, c is not a travel time for
water or contaminants.
The calculated c or log(c) values can be used directly to generate iso-
resistance map by using geostatistical techniques for spatial interpolation in
GIS. The parameter c is related to a qualitative Aquifer Vulnerability Index
(AVI) by a relationship, shown in Table 7.
The AVI rating system of aquifer vulnerability index, originally developed
and applied in Canada (Stempvoort et al., 1992), has been demonstrated by a
successful application in a GIS environment by Stempvoort et al. (1993).
6.3.5. SINTACS Method
The SINTACS method (Civita, 1994; Civita and De Maio, 2000), partially
derived from DRASTIC, retains only the structure of DRASTIC. It evaluates
the vertical groundwater vulnerability using the same seven parameters:
S
oggiacenza
(depth to groundwater),
I
nfiltrazione
(recharge action),
N
onsaturo
(attenuation potential of the vadose zone),
T
ipologia della
