1. October 8 – 10
HYDROGEOLOGICAL SPRING
CHARACTERIZATION IN THE VAJONT AREA
founded by GEORISK project - University of Padova
Paolo FABBRI (*)(**), Mirta ORTOMBINA (*), Leonardo
PICCININI (*) Dario ZAMPIERI (*) & Luca ZINI (***)
(*) University of Padova, Department of Geosciences, Padova, Italy
(**) Institute of Geosciences and Earth Resources, National Research Council of Italy (CNR)
(***) University of Trieste, Department of Mathematics and Geosciences, Trieste, Italy

2. Plan of the talk
1. Hydrogeological situation of principal springs
in Vajont area
2. Isotopic analysis
3. Le Spesse spring hydrogeological analysis
4. V.E.S.P.A. index
5. Le Spesse spring conceptual model

4. Isotopic Analyses

5. Le Spesse and Ega Nass springs

6. Altitude
Recharge
Medium Line
Adriatic Side

8. Monitoring
Le Spesse, EgaNass springs
Hourly monitoring
• Discharge Q(t)
• Temperature T(t)
• Electrical Conductivity EC(t)
cuy
cuy
1
N
N h
1
N
N
ut
u yt
h
y
h
ut
u yt
h
y
0,1,2,.., N 1
h
t 1
1, 2,.., N 1
t 1 h
ruy h
cuy h
cuu 0 c yy 0
CROSS CORRELATION

9. Confidence interval

10. Standardized values
Cross correlation
Confidence interval

11. Standardized values
Cross correlation
Confidence interval

12. V.E.S.P.A. index
• Vulnerability Estimation for Spring Protection Area
V=c( )
Correlation
Factor
Temperature
Factor
Discharge
Factor
GALLEANI L., VIGNA B., BANZATO C. & LO RUSSO S. (2011) - Validation of a Vulnerability Estimator for
Spring Protection Areas: the VESPA index. Journal of Hydrology, 396, 233-245

13. Correlation Factor
c(ρ) = correlation factor
c(ρ) = *u(-ρ) + 0.5u(ρ)+ |ρ|
1
N
N
xi x yi y
i 1
ρ = correlation coefficient
x y
between Q e EC related to one year of hourly
monitoring
u(ρ) = unit step function u
1
0
0
0

14. Temperature Factor
Tmax = year maximum temperature
Tmin = year minimum temperature
Tmax Tmin
1C
2
Discharge Factor
Qmax= year maximum discharge
Qmin = year minimum discharge
Qm = year average discharge
Qm ax Qm in
Qm

15. Spring type
• Our result is (ρ) = -0.1
 type C (homogenization)
Spring type and
prevailing phenomena
Type A — Replacement
Type B — Piston
Type C —
Homogenization
Correlation coefficient
( )
1
0.2
0.2
1
0.2
0.2
V.E.S.P.A. index
β=2
γ = 2.8
c(ρ) = 0.1
VESPA index of V= 0.83
Le Spesse spring = medium
Vulnerability
Very high
High
Medium
Low
VESPA index

16. Conceptual model of
Le Spesse spring was based on:
- A significantly positive correlation at lag 1 rain vs Q,  most
important response in discharge (output) occurs beginning 1 day after a
rainfall event (input)
- During the warm season, the temperature of spring water is colder
than that in the cold season the water discharged is in equilibrium
with the reservoir temperature instead of with the atmospheric
temperature
- Increases in discharge are associated with decreases in EC
discharge increase is essentially due to the local infiltration rather than
infiltration in the true (larger) recharge area
- Correlation coefficient in the VESPA index  type C
“Homogenization”  low level of karstification of aquifer and a
misleading karst response due to local infiltration

17. - isotopic results show a “seasonal isotopic inversion” i.e. that during
summer the spring discharge mainly water infiltrated during the
previous winter
Conceptual model
Slow circulation of the deep reservoir and the high increases in
discharge are due to the local infiltration rather than infiltration in the
true (larger) recharge area
The composition of the spring waters  combination of water from
both the fissured/porous and karstic circulation
Karst is not well developed and its channels are of lesser hydrodynamical
relevance than the fissured/porous part of the reservoir

18. Thank you for
your attention