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WINTER STREAMFLO DYNAMICS IN SNOW DOMINATED CATCHEMENTS - PowerPoint PPT Presentation


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THIS PRESENTATION DESCRIBE MY MSc THESIS WORK. I EVALUAETED AND DEVELOPED A MODEL TO FORECAST THE STREMFLOWS PROBABILITY DISTRIBUTION IN CATCHMENTS SNOW DOMINATED. BOTH IN ITAIAN AND SWISS REGIONS, THE MODEL SEEMS TO WORK REALLY WELL WITHIN ALPINE REGION.

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Presentation Transcript
slide1

UNIVERSITÀ DEGLI STUDI DI PADOVA

Dipartimento ICEA

ENAC – EPFL

Laboratory of Ecohydrology

STREAMFLOW REGIME

IN SNOW DOMINATED

CATCHMENTS

Federico De Piccoli

Relatore

Ing. Gianluca Botter

Correlatore

Prof. Ing. Andrea Rinaldo

Academic year 2011-2012

slide2

INTRODUCTION

Snow covered landscape has acquired notable importance.

In particular in relation with:

ENVIRONMENTAL

ENERGETIC

SOCIAL ACTIVITIES

slide3

WINTER STREAMFLOW DYNAMICS

  • TEMPERATURE GOVERNS THE PRECIPITATION REGIME
  • REDUCED EFFECT OF EVAPO-TRANSPIRATION
  • INCRESING WATER STORAGE RELEASED IN SPRING
  • RETARDING EFFECT IN RELEASE DUE TO SNOW PERSISTENCE

THIS AFFECTS VEGETATION, SOIL AND DISCHARGE DYNAMICS

…a stochastic approach…

slide4

TEMPERATURE IS THE MAIN DRIVER

Image extracted from DTM, Boite closed at Cancia basin

  • THESE THREE ZONES ARE CHARACTERIZED BY:
  • NO SNOW
  • SNOW EVENTS BUT NO ACCUMULATION
  • ONLY ACCUMULATION

3000

2500

2000

1500

1000

[m asl]

Representation in the hypsographic curve.

We divide the fractions as function of Tms

Tms = Mean Seasonal Temperature

Hypsographic Curve

slide5

TO MODEL WINTER STREAMFLOWS …

…WE FOCUS ON ZONES 2 AND 3

slide6

ZONE 2 – A TRANSITION ZONE

2 - ZONE WITH PRIMARLY SNOW EVENTS AND TEMPORARY ACCUMULATION

  • Increasing snowfall probability
  • Area from 1000 to 2100-2300 [m a.s.l]
  • Mean discharge equal to mean precipitation
  • Responsive fraction
slide7

ZONE 3 – THE HIGHER FRACTION

3 - ZONE OF PURE ACCUMULATION

  • Tms < - 4 °C
  • Elevation > 2300 m a.s.l.
  • Negligible snowmelting
  • Accumulation area

The solution is an atom of probability concentrated in zero pdf(Q)=0

slide8

THE THRESHOLD Z*

The idea is to assume the existence of a critical elevation Z* that identifies the different part of the basin

Tms ≈ -2 °C

Z*

CALIBRATION PARAMETER

CLIMATIC INFORMATION

Z*=2000-2300 m a.s.l.

GEOMORPHOLOGY

slide9

STOCHASTIC ANALYTICAL MODEL

Daily precipitation

(marked Poisson process)

Soil moisture dynamic nearby the field capacity

All rainfall is effective

(marked Poisson process)

Threshold Z* - Rescaling CONTRIBUTING AREA

(Calibration parameter Z*)

ANALYTICAL SOLUTION

Discharge delayed by snow persistence

(liner reservoir )

slide10

PIAVE RIVER BASIN

Surface of the mountain part:

3900 km2

Length of the main reach:

156 km

7 testing catchments

Nervesa

slide11

RESULTS – Piave river basin

Fiorentina closed at Sottorovei

Z*= 2100 m a.s.l.

74 % of area

Observed

Analytical with snow

Analytical without snow

slide12

RESULTS – Piave river basin

Coredevole closed at Saviner

Z*= 2130 m a.s.l.

71 % of area

Observed

Analytical with snow

Analytical without snow

slide13

SWISS BASINS

26 catchments minimal anthropogenic influence

7 situated in Alpine region

Some basins present relevant glacial surface

Aletsch glacier in Massa catchment

slide14

RESULTS – Swiss watersheds

Massa closed nearby Blatten bei Naters

Z*= 2210 m a.s.l.

8 % of area

Observed

Analytical modified

Analytical original

Observed

Analytical with snow

Analytical without snow

slide15

RESULTS – Swiss watersheds

DishmaBach closed at Kriengsmatte (Davos)

Z*= 2290 m a.s.l.

38 % of area

Observed

Analytical modified

Analytical original

Observed

Analytical with snow

Analytical without snow

slide16

DISCUSSION OF RESULTS

P[z<Z*]

correlates with the average elevation

Threshold Z* nearly constant in most cases

(independently on geomorphological attributes)

slide17

CONCLUSIONS

  • The model reproduces satisfactorily the probability distributions of the winter discharges observed in both Italian and Swiss basins through the calibration of the only parameter Z*
  • The values of Z* resulting from the calibration of the model with snow, are realistic. Z* is found to be inside the range from 2100 to 2300m a.s.l. in most cases
  • Linear empirical relationships between the fraction of responsive area and the mean and variance of surface heights have been recognized. Such relationships could help improving the predictive power of the model