Investigations on a High Alpine Catchment:
The Sarennes Basin (France)
Eric Martin1, Yves Lejeune1, Etienne Leblois2, Franois Valla3,
Didier Bironeau3, Michel Armand4, Rmy Garon4, Catherine Golaz5,
Emmanuel Ledoux5, and Pierre Etchevers1
The snow cover plays an important role in determining the discharge of mountainous rivers in tem-
perate regions. During spring, high amounts of water are released, so that river discharges are very
sensitive to heavy rain. On the contrary, the snow cover can limit flow hazard if precipitation is (at
least partly) stored as snow in the upper part of the basin. Investigations on a high alpine catchment
are currently under process to quantify the role of the snow cover in river flows during extreme
events. The Sarennes basin (28 km, outlet 1435 m) covers a wide range of elevations (up to 3300 m)
and a small glacier is situated in the upper basin. The CIG distributed hydrological model is used.
The meteorological and snow input are provided by the meteorological analysis system SAFRAN
coupled with the snow model CROCUS. Eighty meteorological zones are defined and are character-
ized by elevation, orientation, and slope. Glacier mass-balance data and additional measurements
were used to validate the snow-cover simulation.
Despite the absence of meteorological measurements in the basin, the meteorological data analyzed
by SAFRAN appeared to be of good quality, except for some storm events. Detailed investigations
of flood episodes showed that they are mostly due to intense snowmelt or rain-on-snow events.
During these episodes a significant part of the basin is covered by snow. Floods due to precipitation
only are extremely rare. A 10-year simulation of discharge showed that the main statistical character-
istics of the discharge are well reproduced. Sensitivity analyses, including the simulation of a rain-
only scenario, highlighted the role of snow as a moderator of floods in autumn and winter.
1
Mto-France, CNRM, Centre d'tudes de la neige, 1441 rue de la piscine F-38406 Saint-Martin d'Hres
CEDEX, France
2 Cmagref, 3bis quai Chauveau, F-69336 Lyon CEDEX, France
3 Cmagref, BP 76, 2 rue de la papeterie, F-38406 Saint Martin d'Hres CEDEX, France
4 Electricit de France, Division technique gnrale, 37 rue Diderot, F-38406 Saint Martin d'Hres CEDEX,
France
5 Centre d'informatique gologique, 35 rue Saint Honor, F-77305 Fontainebleau, France
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