Geography Reference
In-Depth Information
Parameter 5: Q- bonus points for perched aquifer systems
Parameter 6: HP - bonus points for hydraulic pressure conditions (artesian
conditions)
The protective effectiveness (PT) is calculated using the following
expression (Hoelting et al., 1995):
HP
PT
P
P
2
Q
(29)
where, P1 = protective effectiveness of the soil cover; and P2 = protective
effectiveness of the unsaturated zone (sediments or hard rocks)
Parameters P1 and P2 are defined as follows:
P
S
W
(30)
P
2
W
(
R
T
R
2
T
2
Rn
Tn
)
(31)
Based on the German mapping approach, the highest value assigned for
factor W, is 1.75 for an annual groundwater recharge of less than 100 mm
(Hoelting et al., 1995). A modified scale for the factor W was introduced
which reflects the low amounts of groundwater recharge in many areas (Table
8).
6.3.8. PI Method
The PI method is used for mapping the intrinsic vulnerability of
groundwater resources to pollution through a GIS-based approach
(Goldscheider et al., 2000). This vulnerability method is applicable to all kind
of aquifers, but provides special methodological tools for the karst aquifers.
Conceptually, the method is based on an origin-pathway-target model. The
land surface is taken as the origin for the contaminant, the water table in the
aquifer is the target which is vulnerable to contamination, and the pathway
includes all geologic layers in between. Aquifer vulnerability is assessed as the
product of two factors: (i) protective cover (P) and (ii) infiltration conditions
(I). The detailed assessment schemes for the two factors can be found in
Goldscheider et al. (2000), Goldscheider (2004) and Zwahlen (2004).
PI method can be expressed as (Goldscheider et al., 2000):
p
P
I
(32)
