rto012, C.so

Philippe Baveye, Editor-in-Chief

watertiy Es

nerability. The VESPA index is based on a joint analysis of discharge, temperature, and electrical conduc-

ment area is required by the VESPA index. We validated the proposed method using experimental datafrom 12 test springs, and found that the vulnerability estimated by the VESPA index corresponds tothe known vulnerability of the test springs. Four signicant test sites are presented in the paper.

2010 Elsevier B.V. All rights reserved.

the defunda

are met (Pochon et al., 2008): (i) spring discharge varies only withmarked inertia and low amplitude due to recharge events, withoutsignicant relative variation of physicalchemical parameters; (ii)no signicant turbidity is observed, even after intense rechargeevents, and no sediment deposits accumulate in the spring pool;and (iii) bacterial contamination is never detected. High spring vul-nerability is concluded if any of the above conditions is not met.

Using the VESPA index, one can detect the spring vulnerability le-vel or, alternatively, verify the vulnerability determined by meansof other hydrogeological investigation techniques. Consequently,the appropriate procedure for identifying the spring protectionareas, which depend on the hydrogeological environment and localregulatory framework, can be determined.

In the preparatory phase of this research the authors analyzed12 springs located in the SW Alps in the Piedmont region (Italy)to individuate and dene the VESPA index. The level of vulnera-bility has been qualitatively determined by means of conventional

Corresponding author. Tel.: +39 011 564 7648; fax: +39 011 564 7699.

Journal of Hydrology 396 (2011) 233245

Contents lists availab

H

.e lsE-mail address: stefano.lorusso@polito.it (S.L. Russo).groundwater protection. Aquifers are recharged from precipitationand surface waters that percolate through the land surface andbecome part of the groundwater ow system. This water maybecome contaminated as a result of land use practices (Powellet al., 2003; Barry et al., 2009; Schijven et al., 2010). In identifyingthe level of territorial protection required to preserve a spring frompolluting activities in the recharge area, the practical problem iswhether a signicant proportion of the freshly inltrated watercan quickly reach the spring (high spring vulnerability) or not(low spring vulnerability) during or just after a recharge event.

Low spring vulnerability is assumed if the following conditions

turbidity or contamination, the same hydrographs can be evaluatedin different ways by the operators, thus making the spring vulner-ability estimation highly operator-dependent. This is particularlytrue in intermediate situations, where typical hydrograph behav-iors are not so clearly detectable by qualitative analysis.

To standardize spring vulnerability level assessment, we devel-oped the Vulnerability Estimator for Spring Protection Areas(VESPA) index, a vulnerability estimator based on the analysis ofspring hydrographs. The VESPA index uses the discharge (ow)rate Q, groundwater temperature T, and electrical conductivityEC, and requires 1 year of data derived from the spring monitoring.Keywords:Groundwater protection zonesSpringsVulnerabilityVESPA indexPiemonteItaly

1. Introduction

Although uncertain as a process,zones has increasingly become a0022-1694/$ - see front matter 2010 Elsevier B.V. Adoi:10.1016/j.jhydrol.2010.11.012lineation of protectionmental component of

Conditions (ii) and (iii) can be directly veried in a unique way(i.e. water turbidity and/or bacterial contamination are clearlydetectable). However, condition (i) depends on a subjective evalua-tion of the hydrographs by the operator.Without evidence of springThis manuscript was handled by tivity derived from hydrographs. The method requires 1 year of data measured on the spring, andestimates the spring vulnerability for several hydrogeological contexts. No inltration data in the catch-Validation of a Vulnerability Estimator foThe VESPA index

Lorenzo Galleani a, Bartolomeo Vigna b, Cinzia BanzaaDepartment of Electronics (DELEN), Politecnico di Torino, C.so Duca degli Abruzzi 24, 1bDepartment of Land, Environment and Geo-Engineering (DITAG), Politecnico di Torino

a r t i c l e i n f o

Article history:Received 24 March 2010Received in revised form 29 September 2010Accepted 14 November 2010

s u m m a r y

The delineation of groundvulnerability, aquifer propthe use of the Vulnerabilit

Journal of

journal homepage: wwwll rights reserved.Spring Protection Areas:

b, Stefano Lo Russo b,9 Torino, ItalyDuca degli Abruzzi 24, 10129 Torino, Italy

er protection zones around springs requires the assessment of the springes, and preferential inltration zones in the recharge area. We proposetimator for Spring Protection Areas (VESPA) index to quantify spring vul-

le at ScienceDirect

ydrology

evier .com/ locate / jhydrol

The temperature variability is dened as

Hydhydrogeological analysis for each spring. The VESPA index was thuscalculated and compared with the level of vulnerability previouslydetected. The results show that the VESPA index correctly identifythe vulnerability of the analyzed springs. Four signicant test sitesare presented in the paper. The protection areas were determinedaccording to local technical guidelines (Regione Piemonte, 2006).

2. Methods

Analysis of the spring hydrograph responses with respect to theinltrative events in the recharge area forms the basis for ourdeveloped procedure to quantify spring vulnerability.

2.1. Spring hydrograph responses to the inltrative process

Hydrograph analysis is one of the most diffuse and effectiveway to evaluate the properties of an aquifer supplying a spring(Sanz Prez, 1997; Szilagyi et al., 1998; Zecharias and Brutsaert,1998; Halford and Mayer, 2000; Wicks and Hoke, 2000; Pinaultet al., 2001; Mendoza et al., 2003; Fiorillo, 2009). A decay exponen-tial function can be applied to data observed from karst springs, toevaluate the volume and recession of groundwater reservoirs withdifferent permeabilities (Baedke and Krothe, 2001; Grasso andJeannin, 2002; Ford and Williams, 2007; Civita, 2008; Doerigeret al., 2009; Birk and Hergarten, 2010). More comprehensive ap-proaches, including consideration of the physicalchemical param-eters (temperature, EC, isotopes, chemical elements, turbidity)(Dreiss, 1989; Sauter, 1992; Grasso et al., 2003) and tracer tests(Kss, 1998) have proven useful for improving the characterizationof karst hydrogeological systems. Spring hydrographs in non-karstfractured rocks have received less attention, but the same methodscan be applied to the characterization and comparison of crystal-line aquifers (Gentry and Burbey, 2004).

Springs with different aquifer types display different hydro-graphs (Barnes, 1939; Brutsaert and Nieber, 1977; Mangin, 1982;Amit et al., 2002; Malvicini et al., 2005). The aquifer drainage sys-tem can be characterized by an impulse function that transformsthe input (e.g., rainfall or snowmelt) into spring hydrographresponses in terms of discharge, temperature, and EC variations.The impulse functional analysis can then be related to the drainageeffectiveness (i.e. network connectivity) (Plagnes and Bakalowicz,2001; Vigna, 2007; Kresic and Stevanovic, 2009).

2.2. Spring vulnerability estimator (VESPA index)

The joint analysis of water ow discharges, temperature, and ECpotentially offers a useful and replicable way to identify the springvulnerability. To determine the vulnerability index, 1 year of datasampled by automatic sensors every 1 or 2 h and stored in anopportune data logger was considered. This minimum time inter-val helps limit the possible errors associated with the loss of infor-mation provided by the main ood events during the hydrologicalyear (spring and autumn events). The VESPA index is dened as

V cqbc 1where c(q) is the correlation factor, b is the temperature variability,and c is the discharge factor.

2.2.1. Correlation factorThe correlation factor is dened by

cq uq auqjqj 2where q is the correlation coefcient between discharge and con-

234 L. Galleani et al. / Journal ofductivity, computed on the reference time interval t0 = 1 year (onehydrologic year) asThe purpose of the study is to evaluate the VESPA index and ap-ply the described methodology to the identication of protectionzones. In the preliminary phase of this research, several hydro-graphs taken almost continuously over the previous 58 years invarious hydrogeological environments within the Western Alps(12 mountain springs) were analyzed. These unpublished datawere acquired directly through automatic monitoring systems.

To validate the VESPA index, springs were chosen for analysisbased on the following criteria: (i) knowledge of the geological fea-tures and hydrogeological setting of the spring recharge area, asobtained by adequate geological investigations (e.g., survey, tracertests, etc.); (ii) availability of a complete year of discharge,temperature, and EC data, continually collected by automaticsensors; (iii) knowledge of the actual spring vulnerability level,as derived by historical analytical measures of bacteriological con-b Tmax Tmin1 C

26

where Tmax and Tmin refer to the maximum and minimum values,respectively, of the temperature T on the reference time intervalt0 (explored data set: 1 year). Division by 1 C is performed to en-sure that b is dimensionless. Since temperature stability over timeindicates a high aquifer residence time and low vulnerability, themaximum temperature variation is a fundamental parameter forestimating the spring vulnerability. Hence, we use its squared valueto enhance the corresponding weight in the vulnerability index V.

2.2.3. Discharge factorThe discharge factor measures the variability of the discharge

time series, as according to

c Qmax QminQm

7

where Qmax and Qmin are the maximum and minimum values,respectively, of the discharge Q on the reference time interval t0,and Qm is the average discharge given by

Qm 1t0

Z t00

Qtdt 8

2.3. Selection of the test sitesq R t00 QtrtdtR t0

0 Q2tdt

q R t00 r2tdt

q 3

and u(q) is the Heaviside step function

uq 1; qP 00; q < 0

4

The parameter a is a scaling coefcient constrained by 0 6 a 6 1.Since all terms in Eq. (2) are non-negative, c(q) is also non-negative.The key element of the correlation factor is the correlation coef-cient, which can vary in the interval

1 6 q 6 1 5

2.2.2. Temperature variability factor

rology 396 (2011) 233245tamination and/or increased turbidity episodes; (iv) signicance ofthe spring yield (minimum value >5 L/s); and (v) diversity of thesupplying aquifer among the test sites.

3. Results and discussion

3.1. Behavioral models of the drainage network effectiveness

Qualitative analysis of the hydrographs and observed correla-tions between the ow rate, temperature, and EC as a function ofinltration input revealed three broad behavioral categories (typesAC), based on the drainage network effectiveness. The proposedclassication is not directly related to the vulnerability assessment,and only identies the type of response to the inltrative input.

In the highly effective drainage system (type A) during highwater levels (e.g., ood or snow melting period), most of thefreshly inltrated water reaches the spring very quickly, due to

A CB

Fig. 1. Hypothetical examples of spring hydrographic responses to the inltrative processModerate effectiveness, prevailing piston effect. (C) Low effectiveness, prevailing homog

L. Galleani et al. / Journal of Hydrology 396 (2011) 233245 235the presence of open fracture systems, well-developed karst con-duits, or highly permeable horizons, according to the local hydro-geological situation. Generally, these systems show a thinsaturated zone (with limited total spring storage volume) and ahigh degree of permeability. The quick and strong discharge rategrowth after an inltration event is rapidly followed by a fastdepletion, due to the end of the inltrative process. Normal dis-charge conditions are recovered swiftly, within hours or a few days(Fig. 1A). The annual discharge variability index m (in percent)(Meinzer, 1923) is determined by

Table 1Proposed VESPA index intervals for the identicationof the spring vulnerability level.

Vulnerability VESPA index

Very high V P 10High 1 6 V < 10Medium 0:1 6 V < 1Low 0 6 V < 0:1

Table 2Intervals spanned by the correlation coefcient and correlation factor for the three

basic types of spring described in Section 3.1.

Spring type and prevailingphenomena

Correlationcoefcient (q)

Correlationfactorc(q)

Type A replacement 1 6 q 6 0:2 0:2 6 cq 6 1Type B piston 0:2 6 q 6 1 0:1 6 cq 6 0:5Type C homogenization 0:2 6 q 6 0:2 0 6 cq 6 0:2

Table 3Differentiation of allowed land uses in the groundwater protection zones according to thPiemonte, 2006).

Zone Allowed anthropogenic land uses

Total protection zone (TPZ) None. This zone should be fully preseInner protection zone (IPZ) Strongly limited. No excavation and sOuter protection zone (OPZ) Limited. Only minor activities are allom QM QlQa

100 9

where QM, Ql, and Qa are the maximum, minimum, and averageow, respectively. The m is generally quite high and can reach valuesof >100%.

Freshly inltrated water of low salinity tends to replace thegroundwater supplying the spring during the baseow. Therefore,the water chemistry response is usually characterized by a fast andintense reduction in mineralization, highlighted by decreased ECvalues corresponding to the ood peaks. The behavior of thegroundwater temperature is relatively similar to that of the EC:its intense variability is almost synchronous with the ood peaks,and it recovers rapidly after the end of the inltrative processes.The extent and geometry of the peak temperature detectable bya hydrograph is a function of the difference between the ground-water temperature during undisturbed (baseow) conditions andthe temperature of the freshly inltrated water, which variesseasonally.

In the moderately effective drainage system (type B), the springhydrodynamic response can display impulse behaviors (Fig. 1B).Generally, these systems are characterized by fractured or slightlykarstied carbonate aquifers, a thick saturated zone, and a signi-cant total spring storage volume. The discharge variability indicesare generally lower than those in type A systems. Freshly inl-trated water increases the hydraulic head in the saturated zone,and induces a pressure increase in the saturated fractured portionsof the rock mass (fractures and/or karst conduits). This pressureincrease and the corresponding pushing effect tend to mobilizethe resident groundwater. The groundwater is near thermal equi-librium with the aquifer and is characterized by a higher salinitythan the freshly inltrated water. Therefore, a ow discharge andincreased EC and temperature are observed by monitoring thespring (piston effect).

After the inltrative peak, the system is dominated by mixingbetween the resident pre-event groundwater and the freshly inl-trated water. The recovery times of the ood discharge rate, tem-

related to drainage effectiveness. (A) High effectiveness, prevailing replacement. (B)enization.perature, and EC values surveyed at the spring are delayed, andhave a relatively longer duration than those observed in type A sys-tems. Generally, the peak temperature value decreases with in-creases in the elevation above sea level of the recharge area. Thisphenomenon is due to the small difference between the inltrationwater temperature (from rainfall or snowmelt) and the residentgroundwater temperature of the more elevated aquifers.

e Italian and Piemonte region water regulations (Repubblica Italiana, 2006; Regione

rved, enclosed, and with limited access for authorized personnel onlyubsurface work is allowed. Hazardous activities should be re-located if presentwed, and safeguard measures against pollution are necessary for new buildings

Hyd236 L. Galleani et al. / Journal ofIn a low effective drainage system (type C), the hydrodynamicimpulsional response to the inltrative processes is almost absent

Fig. 2. Hydrogeological map of the Piemonterology 396 (2011) 233245(Fig. 1C). The discharge ow displays slow and modest uctuationsthat are delayed up to several months relative to the main rainfall

region (modied after Civita et al., 2004).

events. Chemical parameters (salinity) and the discharge watertemperature usually display a similar trend, with slow and minorvariations. Type C systems generally occur in crystalline and dolo-mitic intensely fracturated rock aquifers or porous media with anabundance of ne matrix. These systems are usually characterizedby an extended saturated zone, with a very low groundwater owvelocity due to limited permeability. Freshly inltrated watermoves slowly in the unsaturated and saturated zones, therebyreaching equilibrium with the aquifer and resident pre-event cir-culating groundwater. Homogenization occurs due to the aquifercharacteristics, and the external output due to the inltrative pro-cess (low salinity and cold water) is strongly reduced.

3.2. Spring vulnerability and V index

Table 1 displays a proposed classication scheme for spring vul-nerability levels based on the VESPA index V. Such classicationarises from the experimental application of the VESPA method tothe 12 springs analyzed in the preparatory phase of this work. Fourof these test sites are presented in Section 3.4. The intervalsbetween the degrees of vulnerability were chosen based on thefour levels of vulnerability required by local regulations (RegionePiemonte, 2006). If a smaller number of classes is required (i.e.three), it may be appropriate to join the High and Very high levels(Table 1), and thus consider V P 1 as the marker for a highly vul-nerable spring.

The VESPA index is dened as the product of three factors, suchthat each factor can increase or decrease the spring vulnerability.These factors include the correlation between the discharge andconductivity, discharge variability, and temperature variability. Ifthe temperature of a spring varies by 0.1 C in 1 year, then the cor-responding variability factor b equals 0.01 and the spring vulnera-bility is strongly reduced by the temperature stability, asintuitively expected. Calculation of the VESPA index is independentof the relationship between recharge (precipitation, snowmelt,stream loss in the recharge area) and discharge hydrographs. There-fore, the vulnerability assessment performed by the VESPA indexdoes not require recharge measures (which can be difcult to per-form in mountainous areas), and only requires measurements col-lected at the spring tapping.

The VESPA approach can enable identication of the effective-ness of the spring drainage systems. Based on the experience gainedon-site, when disturbances due to snow melting or minor oodevents during the year are negligible and annual peaks are clearlydetectable on the discharge hydrographs, the effectiveness of thebasic spring drainage system types (Section 3.1) can be identiedby analyzing the value of the correlation coefcient q. Three typesof springs are identiable using q: replacement (type A), piston(type B), and homogenization (type C) types. Type A systems areidentied by q < 0, since an increased discharge implies a decreasedEC. Eq. (2) shows that typeA corresponds to c(q) = |q|. TypeB springsare identied by q > 0, since an increased discharge corresponds to

0 50 100 150 200 250 300 3500

50

t [days]Rai

nfal

l [m

m/d

ay]

10

15

t [d

rge

[l/s]

t [d

t [d

site

n

L. Galleani et al. / Journal of Hydrology 396 (2011) 233245 2370 50 100 1505

Dis

cha

0 50 100 150

350

400

EC [

s/c

m]

0 50 100 1509

10

11

Tem

pera

ture

[C

]

Fig. 3. Monitoring data of the Ray test

Table 4Summary of VESPA calculated parameters in the four test sites.

Test sitespring

Vulnerabilityindex V

Correlationcoefcientq

q Lowercondenceinterval(95%)

q Uppercondenceinterval(95%)

Correlatiofactorc(q)

Ray 0.0024788 0.11605 0.0953 0.1367 0.058023

Dragonera 0.29237 0.14482 0.1157 0.1737 0.07241

Fuse 14.2771 0.47704 0.4931 0.4607 0.47704Balmetta 28.8469 0.93917 0.9416 0.9366 0.93917200 250 300 350ays]

200 250 300 350ays]

200 250 300 350ays]

. Automatic acquisition interval of 1 h.

Temperaturevariabilityfactor b

Dischargefactor c

Estimatedvulnerability

Aquiferhomogeneity

Effectivenessof drainagenetwork type

0.0841 0.50798 Low High Type C homogenization

0.3364 12.0027 Medium Medium Type B piston

3.7249 8.0348 very high Low Type A substitution

14.44 2.1271 Very high High Type A substitution

Fig. 4. Delineation of groundwater protection zones for the Ray spring with the distance method.

0 50 100 150 200 250 300 3500

50

t [days]

Rai

nfal

l [m

m/d

ay]

0 50 100 150 200 250 300 3500

100020003000

t [days]

Dis

char

ge [l

/s]

0 50 100 150 200 250 300 350160180200220240

t [days]

EC [

s/cm

]

0 50 100 150 200 250 300 3506

7

8

t [days]

Tem

pera

ture

[C

]

Fig. 5. Monitoring data of the Dragonera test site. Automatic acquisition interval of 2 h.

238 L. Galleani et al. / Journal of Hydrology 396 (2011) 233245

HydL. Galleani et al. / Journal ofan increased EC. Eq. (2) indicates that type B corresponds toc(q) = a|q| with a < 1, since type A springs are generally more vul-nerable than type B springs. For the same absolute value of the cor-relation coefcient q, the correlation factor c(q) is smaller for type Bthan for type A. The experimental results veried that a = 0.5 is areasonable choice to individuate type B. Type C springs are identi-

Fig. 6. Delineation of groundwater protection zones with the distance methodrology 396 (2011) 233245 239ed by |q| 0, since the discharge and EC generally show indepen-dent and moderate variations with time. Eq. (2) indicates that thistype corresponds to c(q) 0, and the experimental results indicatedthat jqj 6 0:2 is a suitable interval for a homogenization-type spring.

Table 2 summarizes the values of c(q) for the three basic springtypes. While the correlation coefcient intervals are disjointed, the

for the Dragonera spring. Differentiation of the IPZ and OPZ is opportune.

t

t

t

t

site

Hydcorrelation factor c(q) intervals overlap. The reason for such over-lap is that two springs belonging to different drainage effectivenesscategories can have the same degree of vulnerability.

3.3. Delineation the spring protection area and vulnerability

0 50 100 1500

100

Rai

nfal

l [m

m/d

ay]

0 50 100 1500

500

1000

Dis

char

ge [l

/s]

0 50 100 150160180200220240

EC [

s/cm

]

0 50 100 150

456

Tem

pera

ture

[C

]

Fig. 7. Monitoring data of the Fuse test

240 L. Galleani et al. / Journal ofTo delineate the spring protection areas, additional hydrogeo-logical investigation is needed after numerical assessment of thevulnerability. Particular attention should be paid to the aquiferhomogeneity and to the presence of preferential inltration zonesin the catchment area. For homogeneous or slightly heterogeneousaquifers, the calculated (isochrone) or xed distance methods areconvenient. Vulnerability mapping methods are suitable for delin-eating protection areas for heterogeneous media that supply highlyvulnerable springs, and when preferential inltration zones are de-tected in the catchment area (Adams and Foster, 1992; DoELG/EPA/GSI, 1999; Doeriger et al., 1999; SAEFL, 2000; Daly et al., 2002;Zwahlen, 2004; Pochon et al., 2008). The technical procedures forindividuating a spring protection area vary depending on the localregulatory framework. Following the regulations of the Piemonteregion (Regione Piemonte, 2006), the spring protection area canbe divided into two sub-areas, the inner (IPZ) and outer (OPZ) pro-tection zones, which are characterized by their different allowedland uses (see Table 3). A total protection zone (TPZ) around thespring tapping is always essential.

3.4. Test sites

3.4.1. Hydrogeological characteristics of the Piemonte regionThe Piemonte region is characterized by the arcuate orogenic

belt of the Western Alps (crystalline and carbonate rocks) on itswest side, morphologically connected by extensive alluvial andmorainic fans to the continental plain area in the central and east-ern parts (see Fig. 2). The alpine range continues NE with the cen-tral segment of the chain, and SE with the Ligurian Apennines(Debelmas, 1986; Cadoppi et al., 2007). The mountain area, whichis carved by valleys transverse to the direction of the main struc-tures and convergent towards the barycentre region, displaysincreasing relief energy from SW to NE. In the southern sector ofthe Piemonte, the transition from the plain to the Apennines isgradual, characterized by the intermediate presence of hilly terrig-enous sectors (Monferrato and Langhe) belonging to the Piedmon-tese Tertiary basin. Crystalline and terrigenous rocks show low to

200 250 300 350[days]

200 250 300 350[days]

. Automatic acquisition interval of 1 h.200 250 300 350[days]

200 250 300 350[days]

rology 396 (2011) 233245very low primary permeability, with no considerable aquifer. Somesignicant water circulation is found only in the main fracturedzones along the tectonic discontinuities, and in carbonates (karsticcirculation). Most springs in the mountain sector are generally sup-plied by detritus aquifers covering the crystalline bedrock. Thesediffuse, high quality water resources typically provide moderateto low yields of 130 L/s, and are employed for human consump-tion in most mountain villages. Signicant carbonate structuresand correlated karstic springs are diffuse only in the southern partof the region (Cuneese), and in a limited portion of the northern al-pine chain.

3.4.2. Test site: Ray springThe Ray test site is situated in the Lurisia valley (Roccaforte

Mondov municipality) at 620 m amsl (geographical coordinates44180540N, 7430020 0E, see Fig. 2 for location). The supplying aquiferconsists of intensely fractured carbonate without any developingkarst. The bottom of the carbonate dolomitic aquifer (Trias) is lim-ited by a crystalline basement constituted by quartzites (PermianTrias). The carbonate aquifer is laterally in tectonic contact with thecrystalline basement through a series of sub-vertical normal faultsmainly oriented NS and NWSE. The saturated zone is quite ex-tended, while the unsaturated zone is almost absent. In the overallcatchment area, an extensive protective cover constituted by resid-ual clays is present above the carbonate unconned aquifer.

Land use in the catchment area is predominantly forest. Locally,there are small areas of grassland used for pasture. Small farms andminor roads are also present. Water quality has historically beengood over time. No bacteriological contamination episodes orturbidity increase has been shown, and no signicant variation in

HydL. Galleani et al. / Journal ofdischarge, temperature, or EC has been observed during heavyrainfall. These observations suggest low spring vulnerability.

The monitoring data set starts on June 4th, 2007. The data setrevealed a yearly maximum temperature variation of

t [

t [

t [

t [

st s

Hydwhile the correlation factor identies a prevailing homogenizationphenomenon (type C system), consistent with the qualitativehydrogeological features detected during eld investigations. Asuitable proposal for delineating the protection areas is shown inFig. 4. Due to the lithological features and the intense, uniformfracture distribution, the carbonate aquifer can be consideredhomogeneous overall in the catchment area. A xed distance ap-proach to delineate spring protection areas is suitable (Regione

0 50 100 1500

50

100

Rai

nfal

l [m

m/d

ay]

0 50 100 1500

20

40D

isch

arge

[l/s

]

0 50 100 150406080

100120

EC [

s/cm

]

0 50 100 1504

6

8

Tem

pera

ture

[C

]

Fig. 9. Monitoring data of the Balmetta te

242 L. Galleani et al. / Journal ofPiemonte, 2006). Due to the low degree of vulnerability, to avoidexcessive land use restrictions the protection area will be denedby the minimum proposed by local regulations (200 m upstreamfrom the spring tapping). No differentiation in the protection areais required; therefore, the OPZ coincides with the IPZ.

3.4.3. Test site: Dragonera springThe Dragonera test site is situated in the Roaschia valley (Roas-

chia municipality) at 840 m amsl (geographical coordinates44150590N, 7270160 0E, see Fig. 2 for location). The supplying car-bonate aquifer (TriasCretaceous) is characterized by an intensefracture network and limited karst. It is stratigraphically overlaidby a sequence of carbonate sandstones (Eocene) that highlights astrongly reduced hydraulic permeability. Both the saturated andunsaturated zones are extended. In the catchment area, extensiveoutcrops of carbonate rocks are present, with no protective soilcover. In contrast, soil covers are found over almost all of the detri-tal quaternary deposits. The area is mostly covered by pasture usedfor summer grazing. There are no anthropic settlements (farms),and the viability is only represented by tracks and paths. Thespring discharge responses to inltration events are usually quickduring the increment period to the ood peak, while the dischargeoccurs for a longer time. However, the uctuations in the springdischarge rate during the year are signicant.

The monitoring data set starts on April 29th, 2007. The datahighlights a yearly maximum temperature variation of 0.4 C(average 7.2 C) and EC variation of 30 lS (average 210 lS)(Fig. 5). Normally, increases in the discharge are quickly followedby corresponding increases in the EC and temperature, thus high-lighting a prevailing piston phenomenon. However, melting snowlimits the evidence of this phenomenon on the hydrographs. TheVESPA parameters for the Dragonera spring are reported in Table4. The vulnerability index conrms a medium vulnerability forthe spring, while the correlation factor is in the transition regionbetween a piston process (type B system) and a homogenizationprocess (type C system), as expected from a qualitative analysisof the hydrographs. This is probably due to the mixing effect andthe consequent noise induced by snowmelt, which masks the pis-

200 250 300 350days]

200 250 300 350days]

200 250 300 350days]

200 250 300 350days]

ite. Automatic acquisition interval of 1 h.

rology 396 (2011) 233245ton behavior of the hydrographs.Considering the relative homogeneity of the aquifer supplying

the spring and the medium level of vulnerability, a xed distanceapproach was used to identify the protection zones, according tothe indications provided by local regulations Regione Piemonte,2006. The protection zone can be conveniently subdivided intoan IPZ and OPZ, to avoid excessive land use restriction in the upperpart far from the withdrawal point (Fig. 6). Minimum distances of200 m and 400 m from the spring tapping for the outer boundaryof the IPZ and the OPZ, respectively, can be considered suitable.

3.4.4. Test site: Fuse springThe Fuse test site is situated in the Tanaro valley (Ormea munic-

ipality) at 1475 m amsl (geographical coordinates 44090010 0N,7450050 0E, see Fig. 2 for location). The supplying carbonate aquifer(TriasCretaceous) is intensely fractured with well-developedkarst. The crystalline basement is comprised of quartzites and por-phyroids (PermianTrias). The spring is located on the sub-horizon-tal contact between the carbonate aquifer and the impermeablebasement. The unsaturated zone is quite extended, while the satu-rated zone is strongly limited. The whole catchment area is charac-terized by extensive outcrops of carbonate rocks and a completeabsence of soil and vegetation. Signicant uctuations in spring dis-charge, water temperature, and EC, as well as indications of bacte-riological contamination (even in winter) have been observed.Consequently, the spring appears to be highly vulnerable tocontamination.

The monitoring data set starts on March 7th, 2004, and high-lights a yearly maximum temperature variation of 2.5 C (average5.2 C) and EC variation of 130 lS (average 200 lS) (Fig. 7).

HydL. Galleani et al. / Journal ofThe yield is strongly variable, with an average discharge rate of130 L/s. Various structural discontinuities at the groundwatercatchment and outcrop levels have been observed. Geomorpholog-ical depressions constitute potential locations of concentratedinltration. Three uoroscein tracer tests (see Fig. 8 for locationof injection points) have shown highly variable ow velocities fordifferent injection points in the spring catchment (380800 m/day). These data indicate the presence of rapid ow along intercon-nected networks of highly permeable joints (karstic conduits andfractures). Rapid connections are possible between the springsand surfaces that may be distributed across the whole springcatchment area. Consequently, the groundwater residence timedoes not increase with the distance from the spring in a uniformway, and assimilation of the karstied aquifer to a continuousmedium is inappropriate.

Under these conditions, only the use of a multi-parametergroundwater vulnerability mapping method over the whole catch-ment area enables the effective delineation of protection zones, by

Fig. 10. Delineation of groundwater protection zones for the Balmetta spring. The protesuitable.rology 396 (2011) 233245 243considering the large degree of heterogeneity within the aquifer.However, with reference to the delineation of protection zones atthe Fuse test site, the presence of a preferential inltration zone(doline, sinkhole, interconnected fractures) nearly in the overall re-charge zone led us to consider the entire recharge zone as a protec-tion area, without differentiation (Fig. 8). Land use permissionsmust be stringent, and thus the application of IPZ constraints tothe overall catchment area appears appropriate.

The VESPA parameters for the Fuse site are reported in Table 4.The VESPA index conrms a very high vulnerability for the spring,while the correlation factor indicates a substitution prevailing phe-nomenon (type A system).

3.4.5. Test site: Balmetta springThe Balmetta test site is situated in the Ellero valley (Roccaforte

Mondov municipality) at 960 m amsl (geographical coordinates44150060 0N, 7430000 0E, see Fig. 2 for location). The supplyingaquifer consists of a thin coarse quaternary detritus with high

ction zone coincides with the overall catchment area. IPZ land use restrictions are

and EC variation of 80 lS (average 90 lS) (Fig. 9). The yield is

a replacement generated by freshly inltrated water. If the replace-

Hydment phenomenon prevails, the correlation coefcient betweendischarge and conductivity could approach the limit value ofq = 1. Consequently, the estimated vulnerability V could be high-er than its true value. Second, due to snow melting events, a slowtrend could be present in the measured time series. This trendcould inuence the correlation coefcient in an unpredictableway. A possible improvement of the VESPA index is the detectionand removal of such slow trends, without affecting method perfor-mance. Both of these scenarios can affect the correlation factorc(q), but have a minor effect on the variability of the temperatureand discharge. Evaluation of the VESPA factor from three coef-cients improves method robustness.

4. Conclusions

Without a suitable method for identifying spring protectionzones, it is vital that the operator subjectivity be limited in springvulnerability estimations. Analysis of the linked behavior of thedischarge, temperature, and EC using hydrographs seems to pro-vide a good quantitative estimate of the spring vulnerability. Theseparameters are also useful for identifying the drainage networkeffectiveness and the main phenomena occurring in the aquiferafter the ood peak (prevailing replacement, piston, or homogeni-zation). Vulnerability assessment can be used to dene the ground-water protection zones, according to the hydrogeological situationand local regulatory framework.

The goal of the VESPA index is to provide a numerical assess-ment of the spring vulnerability. Subsequently, the protection areastrongly variable, with an average discharge rate close to 15 L/s.According to local regulations (Regione Piemonte, 2006), due tothe high spring vulnerability, aquifer homogeneity (coarse detri-tus), and lack of effective protective soil cover in the overall catch-ment area, the entire recharge zone is identied as the protectionarea, without differentiation (Fig. 10). Land use permissions areconsequently stringent, and thus the application of the IPZ appearsappropriate.

The VESPA parameters for the Balmetta site are reported inTable 4. The VESPA index conrms a very high vulnerability forthe spring, while the correlation factor conrms a replacementprevailing phenomena (type A system).

3.5. Critical aspects of the VESPA index

Two physical situations can negatively inuence the VESPA in-dex. First, a spring can have a rst phase of piston ow, followed bypermeability, without a signicant protective soil cover. The aquiferoverlays a crystalline substrate constituted by impermeableporphyroids (PermianTrias) that outcrop extensively in the catch-ment area. The saturated and unsaturated zones are limited inwidth. The spring catchment area is characterized by a lack of veg-etative cover. Only in the upper part are summer grazing pasturesare present. Signicant uctuations in spring discharge, watertemperature, and EC, as well as indications of bacteriological con-tamination have been observed, even in winter. Flood peaks corre-spond to quick and signicant depletions of temperature and EC,highlighting a prevailing replacement phenomenon, operated bythe freshly inltrated water in the aquifer. Consequently, the Balm-etta spring appears to be highly vulnerable to contamination.

The monitoring data set starts on June 8th, 2006, and highlightsa yearly maximum temperature variation of 4 C (average 6.8 C)

244 L. Galleani et al. / Journal ofcan be dened by considering the hydrogeological setting as wellas the local regulations. However, we observe that a correct delin-eation of the spring protection areas must always rely on intensivegeological and hydrogeological eld investigations of the rechargearea, mainly aimed at identifying the preferential inltration areas,if present. We have carried out such investigation in the presentedtest sites.

Application of the VESPA method seemed straightforward forseveral reasons. First, the VESPA index allows estimation of the le-vel of vulnerability in a wide range of hydrogeological environ-ments. Second, the spring vulnerability evaluation is based solelyon the analysis of the spring monitoring data, and does not involveany other parameter. Inltration data of the catchment area con-nected to rainfall events, snowmelt, or stream loss, which are dif-cult to evaluate, are not required to compute the V value.Finally, the VESPA method provides reproducible results with amoderate nancial effort.

Recently, the Piemonte regional Water Protection Plan imposedthe development of extensive automatic systems for monitoringthe discharge, temperature, and EC of springs supplying humancommunities (Regione Piemonte, 2007). This provided several datasets for testing and improving the methodology. One year of dataseems to be the minimum time interval necessary for a reasonableestimate of the spring vulnerability using the VESPA index. We ex-pect that our ongoing research will provide signicant input forfurther renements.

Acknowledgements

The authors wish to thank the environmental authority of thePiemonte region for its assistance during the eld survey and forgranting publication of the data, as well as the anonymous review-ers for their useful suggestions and comments. This study waspartially supported by the Piemonte region government.

References

Adams, B., Foster, S., 1992. Land-surface zoning for groundwater protection. J. Inst.Water Environ. Manage. 6, 312320.

Amit, H., Lyakhovsky, V., Katz, A., Starinsky, A., Burg, A., 2002. Interpretation ofspring recession curves. Ground Water 40 (5), 543551. doi:10.1111/j.1745-6584.2002.tb02539.x.

Baedke, S.J., Krothe, N.C., 2001. Derivation of effective hydraulic parameters of akarst aquifer from discharge hydrograph analysis. Water Resour. Res. 37 (1),1319. doi:10.1029/2000WR900247.

Barnes, B.S., 1939. The structure of discharge recession curves. Trans. Am. Geophys.Union 20, 721725.

Barry, F., Ophori, D., Hoffman, J., Canace, R., 2009. Groundwater ow and capturezone analysis of the Central Passaic River Basin, New Jersey. Environ. Geol. 56,15931603. doi:10.1007/s00254-008-1257-5.

Birk, S., Hergarten, S., 2010. Early recession behaviour of spring hydrographs. J.Hydrol.. doi:10.1016/j.jhydrol.2010.03.026.

Brutsaert, W., Nieber, J.L., 1977. Regionalized drought ow hydrographs from amature glaciated plateau. Water Resour. Res. 13 (3), 637643.

Cadoppi, P., Giardino, M., Perrone, G., Tallone, S., 2007. Litho-structural control,morphotectonics, and deep-seated gravitational deformations in the evolutionof Alpine relief: a case study in the lower Susa Valley (ItalianWestern Alps).Quatern. Int. 171172, 143159.

Civita, M., 2008. An improved method for delineating source protection zones forkarst springs based on analysis of recession curve data. Hydrol. J. 16, 855869.doi:10.1007/s10040-008-0283-4.

Civita, M., Lo Russo, S., Vigna, B., 2004. Hydrogeological sketch map of Piemonte(NW Italy) 1:250.000. In: Map Presented at the 32nd International GeologicalCongress (32IGC), Florence, Italy, August 2128.

Daly, D., Dassargues, A., Drew, D., Dunne, S., Goldscheider, N., Neale, S., Popescu, C.,Zwahlen, F., 2002. Main concepts of the European approach for (karst)groundwater vulnerability assessment and mapping. Hydrol. J. 10 (2), 340345.doi:10.1007/s10040-001-0185-1.

Debelmas, J., 1986. Intracontinental subduction and mountain uplift: the exampleof Western Alps. Geologie Alpine 62, 110.

DoELG/EPA/GSI, 1999. Groundwater Protection Schemes. Department of theEnvironment and Local Government, EPA, Geol. Surv. of Ireland, Dublin, 24 pp.

Doeriger, N., Jeannin, P.Y., Zwahlen, F., 1999. Water vulnerability assessment inkarst environments: a new method of dening protection areas using multi-attribute approach and GIS tool (EPIK method). Environ. Geol. 39 (2), 165172.doi:10.1007/s002540050446.

rology 396 (2011) 233245Doeriger, N., Fleury, P., Ladouche, B., 2009. Inverse modeling approach to allogenickarst system characterization. Ground Water 47 (3), 414426. doi:10.1111/j.1745-6584.2008.00517.x.

Dreiss, S.J., 1989. Regional-scale transport in a karst aquifer, part I: componentseparation of springow hydrographs. Water Resour. Res. 25 (1), 117125.

Fiorillo, F., 2009. Spring hydrographs as indicators of droughts in a karstenvironment. J. Hydrol. 373, 290301. doi:10.1016/j.jhydrol.2009.04.034.

Ford, D.C., Williams, P., 2007. Karst Hydrogeology and Geomorphology. Wiley, NewYork. 576 pp.

Gentry, W.M., Burbey, T.J., 2004. Characterization of groundwater ow from springdischarge in a crystalline rock environment. J. Am. Water Resour. Assoc. 40 (5),12051217. doi:10.1111/j.1752-1688.2004.tb01580.x.

Grasso, D.A., Jeannin, P.Y., 2002. A global experimental system approach of karstsprings hydrographs and chemographs. Ground Water 40 (6), 608618.doi:10.1111/j.1745-6584.2002.tb02547.x.

Grasso, D.A., Jeannin, P.Y., Zwahlen, F., 2003. A deterministic approach to thecoupled analysis of karst springs hydrographs and chemographs. J. Hydrol. 271,6576.

Halford, K.J., Mayer, G.C., 2000. Problems associated with estimating ground waterdischarge and recharge from stream-discharge records. Ground Water 38 (3),331342. doi:10.1111/j.1745-6584.2000.tb00218.x.

Kss, W., 1998. Tracing Technique in Geohydrology. Balkema, Rotterdam, TheNetherlands. 600 pp.

Kresic, N., Stevanovic, Z. (Eds.), 2009. Groundwater Hydrology of Springs. ElsevierInc., p. 565. ISBN: 978-1-85617-502-9.

Malvicini, C.F., Tammo, S.S., Walter, M.T., Parlange, J., Walter, M.F., 2005. Evaluationof spring ow in the uplands of Matalom, Leyte, Philippines. Adv. Water Resour.28, 10831090. doi:10.1016/j.advwatres.2004.12.006.

Mangin, A., 1982- Lapproche systmique du karst, consequences conceptuellesmthodologiques [Systemic approach of the karst, conceptual andmethodological consequences]. In: Proc. Reun. Monogr. sobre el karst, Larra,France, November 1982, pp. 141157.

Meinzer, O.E., 1923. Outline of Ground-water Hydrology. US Geol. Survey Water-supply Paper 494, Washington DC.

Mendoza, G., Steenhuis, T.S., Walter, M.T., Parlange, J.-Y., 2003. Estimating basin-wide hydraulic parameters of a semi-arid mountainous watershed byrecession-ow analysis. J. Hydrol. 279, 5769.

Pinault, J.L., Plagnes, V., Aquilina, L., Bakalowicz, M., 2001. Inverse modelling of thehydrological and the hydrochemical behaviour of hydrosystem: characterizationof karst system functioning. Water Resour. Res. 37 (8), 21912204.

Plagnes V., Bakalowicz M., 2001. May it propose a unique interpretation for karsticspring chemographs? In: Proceedings of the 7th Conference on Limestone

for delineating protection zones in Switzerland. Hydrol. J. 16, 12671281.doi:10.1007/s10040-008-0323-0.

Powell, K.L., Taylor, R.G., Cronin, A.A., Barrett, M.H., Pedley, S., Sellwood, J.,Trowsdale, S.A., Lerner, D.N., 2003. Microbial contamination of two urbansandstone aquifers in the UK. Water Res. 37 (2), 339352.

Regione Piemonte, 2006. Regolamento Regionale 11 dicembre 2006 n. 15/R recante:Disciplina delle aree di salvaguardia delle acque destinate al consumo umano(legge regionale 29 dicembre 2000, n. 61). Bollettino Ufciale della RegionePiemonte n. 50 del 14 Dicembre 2006 Supplemento Ordinario No. 1. (in Italia).

RegionePiemonte, 2007. Pianodi TutelaDelle Acque.D.C.R. n. 117-10731, Turin, Italy..

Repubblica Italiana, 2006. Decreto Legislativo 3 aprile 2006, n. 152 Norme inmateria ambientale. Gazzetta Ufciale n. 88 del 14 aprile 2006 SupplementoOrdinario No. 96. (in Italian).

SAEFL, 2000. Groundwater Vulnerability Mapping in Karstic Regions (EPIK).Practical Guide. Environment in Practice. SAEFL, Berne, Switzerland, 56 pp.

Sanz Prez, E., 1997. Estimation of basin-wide recharge rates using spring ow,precipitation, and temperature data. Ground Water 35 (6), 10581065.doi:10.1111/j.1745-6584.1997.tb00178.x.

Sauter M., 1992. Quantication and Forecasting of Regional Groundwater Flow andTransport in Karst Aquifers (Gallusquelle, Malm, SW Germany). PhD Thesis,Univ. of Tbingen, Germany, 149 pp.

Schijven, J.F., Hassanizadeh, S.M., de Roda Husman, A.M., 2010. Vulnerability ofunconned aquifers to virus contamination. Water Res. 44, 11701181.doi:10.1016/j.watres.2010.01.002.

Szilagyi, J., Parlange, M.B., Albertson, J.D., 1998. Recession ow analysis for aquiferparameter determination. Water Resour. Res. 34 (7), 18511857.

Vigna, B., 2007. Classication and operation of aquifer systems in carbonate rocks.Memorie dellIstituto Italiano di Speleologia XIX, 2126. ISBN: 978-88-89897-03-4 (in Italian).

Wicks, C.M., Hoke, J.A., 2000. Prediction of the quality and quantity of maramecspring water. Ground Water 38 (2), 218225. doi:10.1111/j.1745-6584.2000.tb00333.x.

Zecharias, Y.B., Brutsaert, W., 1998. Recession characteristics of groundwateroutow and base-ow from mountainous watersheds. Water Resour. Res. 24,16511658.

Zwahlen, F. (Ed.), 2004. Vulnerability and Risk Mapping for the Protection of

L. Galleani et al. / Journal of Hydrology 396 (2011) 233245 245Hydrology and Fissured Media, Besanon, France (2022 September 2001), pp.293298.

Pochon, A., Tripet, J., Kozel, R., Meylan, B., Sinreich, M., Zwahlen, F., 2008.Groundwater protection in fractured media: a vulnerability-based approachCarbonate (karst) Aquifers, COST Action 620, Final Report. EuropeanCommission Directorate-general XII, Science, Research and Development,Report EUR 20912, COST Action 620, Luxembourg, Belgium.

Validation of a Vulnerability Estimator for Spring Protection Areas: The VESPA indexIntroductionMethodsSpring hydrograph responses to the infiltrative processSpring vulnerability estimator (VESPA index)Correlation factorTemperature variability factorDischarge factor

Selection of the test sites

Results and discussionBehavioral models of the drainage network effectivenessSpring vulnerability and V indexDelineation the spring protection area and vulnerabilityTest sitesHydrogeological characteristics of the Piemonte regionTest site: Ray springTest site: Dragonera springTest site: Fuse springTest site: Balmetta spring

Critical aspects of the VESPA index

ConclusionsAcknowledgementsReferences