Journal of Water Resource and Protection, 2012, 4, 674-685 Published Online August 2012 (
Aquifer Vulnerability Assessment and Wellhead Pr otection
Areas to Prevent Groundwater Contamination in
Agricultural Areas: An Integrated Approach
Stefano Lo Russo*, Glenda Taddia
Department of Environment, Land and Infrastructure Engineering (DIATI), Polytechnic of Turin, Turin, Italy
Email: *
Received June 22, 2012; revised July 25, 2012; accepted August 3, 2012
To implement successful policies for the protection of groundwater and curtail the possibility of water supply contami-
nation, an early evaluation of aquifer vulnerability is needed. Rather than implementing broad restrictions to land use
and effluent discharge, it is more cost-effective and economically favourable to approach protection in a stepwise man-
ner by first assessing the in trinsic vulnerability of the aq uifer when defining the level of land use con trol that is needed
to protect groundwater quality. Following aqu ifer vulnerability evaluation , specific land uses and restrictions sh ould be
defined locally for each water supply with in the wellhead protection areas (WHPAs), which are identified by means of
the groundwater time of travel (TOT). The WHPA should be established for each individual situation, considering the
level of vulnerability of the exploited aquifer. We applied our findings to a specific test site in the Piemonte region of
NW Italy, following the current local procedure for individuating the WHPAs. Using data gathered from this site-spe-
cific exercise, we identified that the procedure allows methods that consider only aquifer parameters to evaluate vul-
nerability and discourages the use of techniques that already compartmentalize soil parameters in the vulnerability as-
Keywords: Groundwater Protection Zones; WHPA; Vulnerability; FEFLOW; Piemonte; Italy
1. Introduction
Groundwater quality in many parts of the world has ex-
perienced significant degradation due to agricultural,
industrial and/or commercial activities. Historically,
damage to groundwater supplies has often occurr ed when
contaminants reach aquifers via the vertical pathway in-
troduced by surface wells. Because of the importance of
groundwater, and the difficulty and expense in remediat-
ing groundwater supplies, steps are now often taken to
prevent initial pollution. Those steps can include pro-
tecting the whole aquifer, as well as the area sur rounding
the surface wellhead, from inadvertent contamination
Use of the term “aquifer pollution vulnerability” began
in the 1970s in France [7] and more widely in the 1980s
[8-10], when it became increasingly clear through re-
search that many aquifers were suffering from significant
anthropogenic contamination resulting in degradation
which compromised usability of the resource. Several
studies have targeted the development of vulnerability
mapping techniques; results of these investigations have
led to new definitions applicable to groundwater protec-
tion issues [11-20]. “Vulnerability” is generally defined
as the (intrinsic) sensitivity of an aquifer to being ad-
versely affected by a contaminant; “groundwater pollu-
tion hazard” relates to the probability that groundwater in
an aquifer will be contaminated at concentrations that
pose a risk to human health or the environment that is
hydraulically connected to the groundwater [4]. An ab-
solute (numeric) index of aquifer pollution vulnerability
is far more useful than relative indicators for all practical
applications in land-use planning and effluent discharge
control. With this goal in mind, several methods pro-
posed in the literature are focused on vulnerability as-
sessment. They vary by the parameters and mathematical
expressions considered. GOD [10] and modified GOD
[4], DRASTIC [9], EPIK for karst settings [21] and
SINTACS [22] are acronimous of the most widely util-
ized processes. Each method can provide a numerical
index which is generally correlated to a vulnerability
class definition that is qualitatively described at the end
of the evaluation process (usually high, moderate, low
and negligible). The selection of the appropriate meth-
odology depends on the hydrogeological setting and
*Corresponding a uthor.
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available data. It is quite possible to have high vulner-
ability but no pollution hazard because of the absence of
significant subsurface contaminant load, or vice versa [4].
Following this approach, an inventory of potential sub-
surface contaminant load is necessary to design adequate
safeguards for specific situations.
In order to protect the groundwater intercepted by a
production well, it is essential to develop a thorough un-
derstanding of the groundwater flow system and to de-
lineate the area surrounding the well where potential
contamination could occur [23]. The proximity of the
land-use activity to a gro undw ater sup p ly (well or sp r ing)
is a critical factor in determining the potential for con-
tamination [24,25]. More specifically, the pollution threat
depends on 1) whether the activity is located within the
(subsurface) capture area of the supply and 2) the hori-
zontal groundwater flow time in the saturated aquifer. In
order to completely eliminate the risk of unacceptable
pollution of a supply source, all potential activities that
might lead to contamination in the recharge zone would
have to be prohibited. Th is will often be unsustainable or
economically impractical, especially in developed areas
with pre-existing land-use constraints [26]. It may be
more practical to segregate the recharge zone, so that the
most stringent land use restrictions will only be applied
in areas closer to the source [27].
To achieve the necessary segregation, a series of gen-
erically concentric surface zones around the groundwater
source can be defined through knowledge of local hy-
drogeological conditions and the characteristics of the
groundwater supply source itself [28]. Once delineated,
the protection areas may be managed to prevent con-
tamination and for clean-up if contamination occurs. The
supply protection areas must protect the source against
persistent contaminants as well as those that degrade
over time [29]. Both are necessary for comprehensive
protection. Such an area is referred to as the wellhead
protection area (WHPA). The US EPA [30] early de-
fined a WHPA as “the surface and subsurface area sur-
rounding a water well or well field, supplying a public
water system, through which contaminants are reasona-
bly likely to move toward and reach such water well or
well field”. Several WHPA delineation methods exist,
differing in their degree of complexity and precision.
Naturally, the integration of more geological and hydro-
geological characteristics of the study area increases the
accuracy of any given method. These methods include
Arbitrary fixed ra dius
Calculated fixed radius
Simplified variable shapes
Flow system mapping with uniform flow equation
Analytical flow/particle-tracking tools
Numerical flow/transport models
Since the early 1990s, many WHPA studies have been
completed, some of which have stressed the necessity of
integrating various hydrogeological characteristics into
the delineation methods. A comparative review of WHPA
delineation methods is provided in Paradis et al. [31].
From a practical perspective, the most appropriate me-
thod for WHPA delineation should be one that simpli-
fies the flow system as much as possible while preserve-
ing its geologic and hydrologic characteristics [32,33].
The WHPA can be referred to as the zone of contribu-
tion, i.e., the two-dimensional (2D) projectio n to the land
surface of the aquifer volume containing all the ground-
water that may flow toward a pumping well over an infi-
nite time period. The zone of travel is defined within the
zone of contribution and can be described as an isochrone
indicating the transfer time—time of travel (TOT)—nec-
essary for water or a conservative contaminant to reach
the well from that location. The TOT will depend on the
pumping rates and the aquifer characteristics such as
transmissivity, hydraulic gradient, porosity and aquifer
thickness. The level of aquifer vulnerability should ad-
dress the selection of TOT for identification of WHPAs.
In fact, water wells exploiting low-vulnerability aquifers
can be protected by limited WHPAs (low TOT values)
without compromising the level of the protection. Con-
versely, wells tapping vulnerable aquifers require ex-
tended WHPAs (high TOT) to ensure adequate safe-
guards are in place. The proper evaluation of aquifer
vulnerability and the selection of a suitable TOT for
WHPAs is thus very important to avoid over- or under-
estimating the level of land protection that is required.
This selection is especially significant in agricultural
areas where fertilizers, agrochemicals and pesticides are
intensively utilized [34]. Therefore an effective compre-
hensive protection strategy for groundwater quality
should integrate the assessment of the aquifer vu lnerabil-
ity with the WHPAs in a suitable way.
As early as 1980 the European Union developed a di-
rective concerning the preservation of water quality for
human consumption [35]. In concordance with that di-
rective, the Italian Government, in the 1980s, developed
a national regulatory framework for the protection of
groundwater resources, including the need for WHPA
delineation for water supplies (wells, springs and surface
water acquisition points) [36]. Subsequent European di-
rectives designed to protect the subsurface environment
from unacceptable contamination [37-40] were progres-
sively incorporated into the Italian national legislative
framework [41-43]. These new legislative directives in-
troduced novel procedures and scientific aspects to
groundwater protection policies. Based on these newly-
defined perspectives, some Italian regional governments
implemented specific groundwater resources programs to
safeguard water supplies within their territory. Through
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Copyright © 2012 SciRes. JWARP
specific regulations [44] the Piemonte region environ-
mental authority (NW Italy) tried to ensure proper align-
ment between aquifer vulnerability and the WHPAs de-
Actions taken to preserve and protect groundwater re-
sources within a WHPA, particularly those encompassing
limitations on certain agriculture practices, must be ap-
proached in a collaborative fash ion with local agriculture
stakeholders, and must take into account available best
practices and supporting scientific data.
In this paper we tested 1) the current comprehensive
technical framework for individual WHPAs in the
Piemonte region on a representative case study. We
highlighted some critical and 2) we proposed a limited
review of the adopted methodology.
2. Methods
2.1. Identifying WHPAs in the Piemonte Region
(NW Italy): Techniques and Regulations
As implemented in the Piemonte region [44], a WHPA
consists of three different decreasing protection levels
situated at increasing distances, respectively, from the
well (Table 1).
The WHPA has to be defined through a procedure
based on existing information and specific surveys. The
regulations procedure individuating the WHPA requires
an initial geological and hydrogeological general invest-
tigation of the area. It is followed by evaluation of aqui-
fer vulnerability, assessment of the aquifer hydrodynamic
parameters by means of appropriate pumping tests, cal-
culation of the isochrones through analytical or numeri-
cal models and, finally, an inventory of activities that
have the potential for causing contamination within the
WHPAs. These data allow for delineation of the WHPA
and definition of the land use management plan within
the area. Once defined, land use restrictions are con-
trolled by the water supply company managing the well
in cooperation with the regional environmental authority.
The WHPA is usually divided into two sub-areas,
namely the inner protection zone (IPZ) and the outer
protection zone (OPZ). The IPZ is always individuated
by the 60-d isochrone, while the TOT that identifies the
OPZ depends on the vulnerability of the exploited aqui-
fer. There are four generally accepted vulnerability cate-
gories: Very High, High, Medium and Low. For low aq-
uifer vulnerability the OPZ must be calculated using the
180-d isochrone; the remaining vulnerability categories
are determined by utilizing the 365-d isochrone. It should
be noted that regulations do not provide any specifica-
tions about the methodology for assessing aquifer vul-
nerability. The suitable method must be decided on a
case by case basis. For WHPAs overlaying agricultural
areas, a specific fertilizer and phytosanitary management
plan must be developed which integrates the general land
use management plan. It should ensure the safe applica-
tion of fertilizers, agrochemicals and pesticides, taking
into account the attenuation capacity of the soil cover
with respect to groundwater pollution. Determination of
this protection capacity must consider at least the fol-
lowing soil parameters: texture, skeleton, soil depth and
cracks. These soil data are generally available for the
general region. Soil protection capacity has been evalu-
ated by IPLA [45] and is currently available digitally via
the internet. In areas for which historical data are not
available, a specific site evaluation should be developed
(minimum 1 soil profile/2 ha of WHPA). Four soil pro-
tection capacity categories have been established: very
high, high, medium and low. By combining the aquifer
vulnerability and the soil protection capacity within the
WHPA in a suitable manner (Table 2), four levels of
land use restrictions are identified and the corresponding
agricultural land use limitations have been specifically
defined (Table 3).
2.2. Test Site: The Castagnole Well
The procedure for developing a specific WHPA, as de-
scribed in Section 2.1, was tested on a water well supply
ing the Castagnole municipality, located 20 km south of
the Turin urban area (see Figure 1), which is the capital
of the Piemonte region (well geographical coordinates
are 45˚54'01.93''N, 7˚33'23.55''E). The elevation of the
site is 244 m asl. The tested well is 88 m deep. The di-
Table 1. WHPA differentiation and permitted land use s ac c ording to the Italian water regulations (modified after [42]).
WHPA zone Individuating criteria Land uses
Total protection zone (TPZ) Fixed radius (10 m minimum) None. This zone should be fully preserved, imp ermeabilized,
enclosed, and with limited access for authorized personnel only.
Inner protection zone (IPZ) Time of tra vel (60-d isochrone) Strongly limited. No excavation and subsurface work is allowed.
Hazardous activities should be re-located if they are present.
New buildings construction is prohibited.
Outer protection zone (OPZ) Time of travel (180-d and 365-d isoch rones for
low vulnerability aquifers or medium, high and
very high vulnerability aquifers, respectively)
Limited. Only minor anthropogenic activities are allowed, and
safeguard measures against groundwater pollution are
necessary for existing and new buildings.
Table 2. Identification of the land use protection levels required within the WHPA in the agricultural areas by the association
of aquifer vulnerability and soil protection capacity. See Table 3 for details concerning authorized land uses and agricultural
practices (modified after [44]).
Soil protection capacity (related to groundwater pollution)
Very high and high Medium and low
Low aquifer vulnerability Level 4 (minimum protection) Level 3
Medium aquifer vulnerability Level 3 Level 2
High and very high aquifer vulnerability Level 2 Level 1 (maximum protection)
Table 3. Authorized land uses and agricultural practices within the WHPAs as indicated by the protection levels derived by
the association of aquifer vulnerability and soil protection capacity (see Table 2) (simplified and modified after [44]).
Water supply protection lev el In the inner protection zone (60 d isochrone) In the outer p rotection zone (180 d or 365 d isochrone)
Level 1 (maximum protection) Pasture, fertilizers and phytosanitary products
are fully prohibited
Fertilizer balance plan is mandatory.
Nitrogen effluent discharges are limited below
yearly 170 K g / ha maximum value.
Phytosanitary products are authorized under
European regulations for organic farming [46]
Level 2
Fertilizer balance plan is mandatory. Nitrogen effluent
discharges must be less than the maximum annual value
of 170 Kg/ha. Phytosanitary products are authorized
under European regulations for o rganic farming [46]
Same as the IPZ. A wider range of ph ytosanitary
products and weed practices can be allowed on a
case by case basis under specific conditions and
regulations defined by the public surveillance
Level 3
Fertilizer balance plan is mandatory. Nitrogen effluent
discharges must be less than the maximum annual value
of 170 Kg/ha. Phytosanitary products are authorized
under European regulations for organic farming [46].
A wider range of phytosanitary products and weed
practices can be allowed on a case by case under specific
conditions and regulations defined by the public
surveillance authority.
Same as the IPZ
Level 4 (minimum protection)
Fertilizers balance plan is mandatory. Nitrogen effluent
discharges must be less than the maximum annual value
of 170 Kg/ha. Phytosanitary products and weed practices
are allowed on a case by case basis under specific
conditions and regulations defined by the public
surveillance authority.
Same as the IPZ
ameter of the casing is 650 mm. The well is cemented
from the surface to a depth of 28 m. Three screened sec-
tions are located in producing sand-gravel layers between
depths of 46 - 50 m, 67 - 69 m and 78 - 81 m. The undis-
turbed water level of the confined aquifer (without any
pumping) is at 242 m asl on the well vertical (Figure 2).
The withdrawn groundwater is analyzed by regional
sanitary authorities twice a month to control the chemical
and bacteriological parameters according with Italian
regulation for water intended for human consumption [36,
38-40]. Since 1990 no organic or inorganic pollution was
2.3. Geology Site Description
The Castagnole area is mainly developed on the outwash
plain comprised of several glaciofluvial coalescing fans
connected to the Pleistocene-Holocene expansion phases
east of the Alpine glaciers. The substrate of the outwash
plain outcrop corresponds to the Torino Hill and consists
of a Cenozoic ter rigenous marine su ccession deposited in
an episutural basin [47] (see Unit 3 in Figure 1). As a
result of a complex Pliocene-Holocene evolution charac-
terized by the deposition of continen tal sediments related
to the dynamic evolution of the Plio-Pleistocene “Villa-
franchian” glaciolacustrine facies [48] and the Pleisto-
cene-Holocene expansion phases of the main Alpine gla-
ciers, the geological setting of the plain is characterized
by a strong geographical anisotropy.
The hydrogeological setting can be described with a
high degree of confidence due to the large number of
wells drilled in the plains area [49]. Dow nhole log data in
the study area indicate the presence of two lithologic
zones with distinct hydraulic properties. On the well ver-
tical it is possible to identify Units 1 and 2 (Figure 2),
which are described in greater detail.
Copyright © 2012 SciRes. JWARP
Figure 1. Hydrogeological map of the southern Turin area and location of the study site (modified after [50]).
Figure 2. Schematic hydrogeological cross section of the study site (see Figure 3 for location). i: gradient of confined aquifer
potentiometric surface.
Copyright © 2012 SciRes. JWARP
Unit 1—(Middle Pleistocene-Holocene; from the sur-
face to a depth of 28 m). Continental alluvial cover is
composed mainly of coarse gravel and sandy sediments
(locally cemented) derived from alluvial fans aggraded
by the Alpine rivers flowing downgradient to the east. At
the base of the unit there are clayey lacustrine deposits
(ca. 4 - 5 m thick) that extend over the entire area and act
as a confining layer between Units 1 and 2. The base of
Unit 1 (erosional surface) dips gently (0.5%) to the east
and overlays Unit 2 .
Unit 2—(Early Pliocene-Middle Pleistocene; from a
depth of 33 m). Fluvio-lacustrine facies usually referred
to as the “Villafranchian”, consisting of fine-grained
sediments (sand, silt and clay with interbedded gravel)
divided into several sedimentary bodies. Other portions
of the plain highlight the heteropic relationships with
sediments originally deposited in a shallow marine envi-
ronment and traditionally defined as Sabbie di Asti
and/or Argille di Lugagnan o. They are mainly composed
of fossiliferous sand-clay layers with subordinate fine
gravel and coarse, sandy marine layers, or by quartz-
micaceous sands with no evidence of fossils. The top of
Unit 2 has been eroded away and covered by the lacus-
trine facies and alluvial deposits of Unit 1.
2.4. Hydrodynamic Characterization of the
In order to numerically model groundwater flow, an ac-
curate characterization of the site’s hydrogeological pro-
perties, groundwater flow direction and hydraulic gradi-
ent (the potentiometric surface), and the hydrodynamic
properties (transmissivity, hydraulic conductivity, stor-
age coefficient) is required. The unconfined aquifer that
extends over the entire plain, including the study site
location, is hydraulically connected to the main surface
water drainage network (i.e. Chis ola River and Po River).
The potentiometric surface, 2 m below ground level,
shows a W-to-E gradient of 0.2%. The saturated thick-
ness of the unconfined aquifer at the site is about 26 m.
In order to characterize the hydrogeological properties
of the aquifer in Unit 1, an appropriate step drawdown
test was initially performed on a 30 m deep well located
less than 1.5 km from the site. The test data yielded a
transmissivity (T1) of 7.3 × 10–3 m
2/s. The hydraulic
conductivity (K1 = 3.65 × 10–4 m/s) was calculated as-
suming an average saturated thickness of 20 m. On the
basis of a constant-rate pumping test, the storativity (S1)
was assumed to be 0.20.
A confined aquifer system occurs in Unit 2. The avail-
able subsurface data indicate that the direction of
groundwater flow and the po tentiometric gradient (0.2%)
in the Unit 2 aquifer system are similar to those in the
unconfined aquifer of Unit 1. In the productive well the
potentiometric surface of the confined aquifer stabilizes
31 m above the top of Unit 2, just 2 m below the
ground’s surface, which is roughly equivalent to the
value measured in the overlaying Unit 1. The hydraulic
transmissivity (T2) of the Unit 2 aquifer system (7.52 ×
10–3 m2/s) was determined by means of a specific step-
drawdown test in the studied well. The storativity (S2)
was calculated as 10.6 × 10–4.
2.5. Modelling Study of the Aquifers
The modelling study was performed using the finite-
element FEFLOW® package developed by Diersch [51].
A conceptual model with three layers was simulated us-
ing physical properties appropriate to the hydrogeology
of the formation. Layer 1 represented the unconfined
aquifer in Unit 1, Layer 2 corresponded to the 5 m thick
impermeable clay layer at the base of this aquifer and
Layer 3 represented the confined aquifer system of Unit
2. The distribution of the different layers in the model
area was determined from topographic elevation data for
the different geological units as listed in the regional au-
thority database [49].
A plan view of the area covered by the computational
grid (about 27.82 million m2; 14,133 elements and 9800
nodes) is shown in Figure 3. The ground surface ranges
from 253 m at the NW mesh vertex boundary to 240 m at
the SE vertex. The horizontal dimensions of the model
grid are 5238 m (SW-NE) and 4334 m (NW-SE). The
average mesh spacing in the modelling domain is 70 m,
which was refined to 8 m in the central area close to the
well to provide enhanced estimation of potentiometric
disturbed surface and the wellhead protection area iso-
chrones. The north and south boundaries are set as no-
flow boundaries. The east and west boundaries are con-
stant-head boundaries (Dirichlet conditions). These lev-
els were determined by initially calibrating the model
against the steady-state groundwater heads obtained from
a potentiometric surface map [50] and a specific survey
of the area. An assumption of the model was that the
system was closed to fluid flow at bottom (Layer 3 is set
200 m thick). The system has only recharge from rainfall
and the ground surface is set as a prescribed flux bound-
ary recharged by rainfall. An infiltration rate of 5.7 ×
10–4 m/day is used in the model, which is equivalent to
25% [52] of the annual rainfall of 834 mm.
The simulations were run assuming steady-state condi-
tions for groundwater flow. The withdrawal rate on the
tested well (12 L/s) corresponds to the abstraction peak
conditions. In reality, such conditions never actually oc-
cur because of variable (transient) water demand and the
presence of a groundwater storage tank. Therefore, the
actual impacts to the aquifer in terms of potentiometric
surface changes due to well pumping will be less than
Copyright © 2012 SciRes. JWARP
Figure 3. Plan view of the site and modelling domain overlain onto the topographical map. Potentiometric surface for the
Unit 1 unconfined aquifer (continuous line s) and Unit 2 confined aquifer (dashed line s) under undisturbed conditions (in me-
ters above mean sea level; m asl). Contour spacing: 1 m. Shown is the location of the cross section given in Figure 2.
those computed by the model. As a result, the WHPAs
individuated by means of the calculated isochrones will
be slightly overestimated and thus conservative relative
to aquifer protection.
2.6. Aquifer Vulnerability and Soil Protection
Qualitatively, the unconfined aquifer accessed in Unit 1
is considered highly vulnerable to pollution because of
its shallow depth and the direct connection with the sur-
face water drainage network. The confined aquifer in
Unit 2, on the other hand, is only moderately vulnerable
to pollution, due both to depth (on average, the top of
Unit 2 is situated at 30 - 35 m) and to several clay inter-
layers subdividing the formation. Only damaged or im-
properly constructed wells could introduce contaminants
to this system of confined aquifers. To identify the suit-
able isochrone values delineating the WHPAs, aquifer
vulnerability must be numerically defined. To achieve
this, the modified GOD method [4] was selected as a
suitable method. In fact, more sophisticated vulnerability
assessment methods such as DRASTIC or SINTACS are
not suitable because they already include in the aquifer
vulnerability assessment the soil parameters affecting the
protection capacity. Therefore the required protection
level identified by means of the procedure described in
the Table 2 could be erroneously evaluated. The GOD
technique assigns numerical values between 0 and 1 to
the Groundwater confinement level (i.e. G value), the
lithological characteristics and the degree of consolida-
tion of the vadose zone or confining layers (i.e. Overly-
ing strata or O value) and depth to the groundwater table
for unconfined aquifers, or to the strike for confined aq-
uifers (i.e. Depth or D value). No soil parameter is con-
sidered. The resulting GOD value that identifies aquifer
vulnerability is calculated by the multiplication of these
three parameters. Due to the relative homogeneity of the
aquifer over the entire modelling domain, the GOD value
has been computed on the well vertical. At the test site,
the Unit 2 aquifer has a G value of 0.2 (confined aquifer),
an O value of 0.8 (alluvial and fluvio-glacial sands and
Copyright © 2012 SciRes. JWARP
gravels) and a D value of 0.7 (depth of 20 - 50 m), re-
sulting in a GOD value of 0.112, which indicates low
vulnerability. Therefor e, th e OPZ can be identified by the
180-d isochrone.
The modelling domain overlays different soil units
characterized by an appropriate level of protection against
groundwater pollution. Figure 4 and Table 4 highlight
the result of a GIS analysis of the soil units over the
whole modelling domain.
3. Results and Discussion
The calculated WHPA for the test site is delineated in
Figure 5. The 60-d isochrone (IPZ) covers about 4334
Figure 4. Soil units in the modelling domain (modified after [45]). See Table 4 for description.
Table 4. Soil units in the modelling domain and corresponding degree of soil protection capacity (Simplified and modified
after [45]).
Soil unit Soil classification Area (m2 and %) in
the modelling domainSoil protection capacity
(related to gro undwater pollution)
U0677 Typic endoaquept, coarse-loamy, mixed, nonacid, mesic 4,248,990 (15.3% ) Low
U0095 Dystric fluventic eutrudept, coarse-loamy, mixed, nonacid, mesic 8,439,617 (30.3%) Very high
U0118 Psammentic haplustalf, coarse-loamy, mixed, nonacid, mesic 580,037 (2.1%) Very high
U0583 Typic endoaquept, coarse-loamy, mixed, nonacid, mesic
(70% UTS—Unit territorial surface)
Aquic dystric eutrudept, coarse-loamy, mixed, nonacid, mesic (30% UTS) 5,149,067 (18. 5%) Medium
U0586 Dystric eutru d e p t , coarse-loam y, m ixed, nonacid, mesic (60% UTS)
Aquic dystric eutrudept, coarse-loamy, mixed, nonacid, mesic (40% UTS) 2,139,180 (7.7%) Very high
U0662 Typic endoaquept, coarse-loamy, mixed, nonacid, mesic (70% UTS)
Aeric endoaquept, coarse-loamy, mixed, nonacid, mesic (30% UTS) 4,996,325 (18. 0%) Medium
U0678 Fluventic dystrudept, coars e-loamy, mixed, acid, mesic 2,269,850 (8.2%) Medium
Copyright © 2012 SciRes. JWARP
Figure 5. Wellhead protection areas identified by means of isochrones.
m2, while the 180-d isochrone (OPZ) covers 11,734 m2.
Considering both the aquifer vulnerability (low) and the
medium soil protection capacity of the soil unit overlaid
by the WHPA (U0678), the corresponding level of pro-
tection was calculated as Level 3 (Table 2). Given this
level of protection, certain restrictions on agricultural
practices must be observed (Table 3). The calculated
WHPA includes a minor road and therefore additional
precautionary measures should be developed in order to
prevent co ntaminant migratio n from the surface due both
to accidental spills and infiltration of dust and water run-
ning off the road surface that might carry contaminants
(e.g., petroleum hydrocarbons, metals). Safety measures
applied along the motorway would include:
a) Using catchments and channelling to collect rain
water that contacts the road surface, or any other fluid
that is accidentally released;
b) Transport of collected fluids to monitoring basins
and, after verifying the absence of contamination, send-
ing those liquids for final disposal (water drains or
streams). If contaminants are found to be present at con-
centrations exceeding established criteria, standards or
benchmarks, the fluids will be sent to treatment plants;
c) The final destination of clean water should be out-
side, and downgradient, of the WHPA.
The specific measures that are instituted to safeguard
the WHPA should be managed by the regional environ-
mental authority in cooperation with the farmers, the
water well managing company and the road maintenance
4. Conclusions
An effective and economically-sustainable land man-
agement strategy to protect subsurface water resources
from anthropogenic po llution must combine gen eral saf e-
guards applied to the whole aquifer recharge area with
specific local land use restrictio ns in the proximity of the
abstraction point (i.e. WHPAs). The first component, i.e.
general protection strategies, can be derived through an
extensive, broad-scale investigation, taking into account
aquifer vulnerability, while data for the second compo-
nent can be obtained using site-specific investigations
within a narrowly-defined area proximal to the abstract-
tion point. The importance of considering these two
components in an integrated fashion cannot be under-
stated. In particular, the selection of TOT for WHPA
delineation is critically linked to the anticipated vulner-
ability of the aquifer in question.
This study has highlighted a technical approach de-
veloped in the Piemonte region, and designed to protect
drinking water wells. An important aspect of this ap-
proach was the integration of broad-scale aquifer vul-
nerability assessment with localized WHPA delineation.
Copyright © 2012 SciRes. JWARP
The method has been successfully tested on a community
drinking water well and is both affordable and effective.
However, for this method to be accepted for broad ap-
plication, additio nal refinement is needed in certain areas.
In particular, improved specifications should be provided
to allow the user to more confidently select an appropri-
ate aquifer vulnerability assessment method. The present
version provides little guidance, leaving the selection to
professional subjectivity and experience. However, cur-
rent regulations combine the vulnerability level with soil
protection capacity, thus discouraging the use of tech-
niques that already compartmentalize soil parameters in
the vulnerability assessment (e.g. DRASTIC and SIN-
TACS). Given this constraint, only methods that consider
aquifer parameters (i.e. GOD) seem suitable to evaluate
vulnerability. Future iterations should simplify the pro-
cedure to individuate the necessary level of protection
within the WHPA if soil protection capacity is directly
included in the aquifer vuln erability assessment.
5. Acknowledgements
The authors thank the environmental authority of the
Piemonte region for their assistance during the field sur-
vey, the modelling, and for allowing publication of the
data. This study was partially su pported by the Piemonte
regional Government and by SMAT S.p.a. integrated
water services company.
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