9oct 2 fabbri-hydrogeological spring


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9oct 2 fabbri-hydrogeological spring

  1. 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. 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
  3. 3. Isotopic Analyses
  4. 4. Le Spesse and Ega Nass springs
  5. 5. Altitude Recharge Medium Line Adriatic Side
  6. 6. 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
  7. 7. Confidence interval
  8. 8. Standardized values Cross correlation Confidence interval
  9. 9. Standardized values Cross correlation Confidence interval
  10. 10. 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
  11. 11. 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
  12. 12. 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
  13. 13. 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
  14. 14. 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
  15. 15. - 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
  16. 16. Thank you for your attention