+103
10/0
Ga
50 m
0
ler
+97
WATER TABLE
100 m
ie de la Co r de
+63 11/47 11/34 = 10/16
KARST
6
c ip
ale
+51
G al
er ie
p r in
One might think that all of the water that falls in the Susanfe Valley eventually flows out through the Encel Gorge, the steep river gorge at the bottom of the valley. The area’s unique geology, however, allows a large percentage of the surface waters to seep rapidly into the ground via faults and cracks. In passing, the dissolving action of these waters on the carbonate bedrock creates cavities ; these eventually merge to form networks of caves and galleries through which the waters gather and flow (Karst). The real watershed, the groundwater basin, is therefore significantly different from the topographic watershed.
+37 Entrée supérieure
Ré 14/0
+36 se
au
fo
Di v
ss
Si
il e
4/20 = 5/0 = 11/0
er t
5/75 5/67 = 7/0
ic u
6/3 5/70 = 6/0 7/7 = 8/0 7/9
le
ph
11/6 = 13/0
on 2
+20 +17
G
r ale
ie
d’e
ré nt
13/21
3/1 = 4/0
2/0 = 3/0 = 14/16
Sip
n ho
+21 +21
8/60
1
Ré s e a
u C ar o
8/45 = 12/0
uge
Go
to
Ri
ve
r.. . 12/18 +22
e
V1.0 28.12.2003 / CP
5 © M. & R. Beaud
SPRINGS The Bonavau Cirque contains some twenty springs (7). Their output is variable and highly dependent on rainfall and snowmelt. Some of the springs, such as Fontaine Blanche or the Grande Source are dry for most of the year, which allows for their extensive exploration by speleologists(1, 2, 3 et 7). When it is flowing, however, the impressive Fontaine Blanche (5) waterfall can spill up to 750 litres per second.
HYDROGEOLOGY
1/0 = 2/23
±0
Cabane de Susanfe
VS 113/4 Résurgence de Fontaine Blanche There are two distinct hydrogeological watersheds in the Susanfe Valley. These watersheds, identified by tracer tests, separate at the bottom of the valley, with the southern waters (4) draining towards the Fond de la Combe in France and the northern waters pouring out of the springs at the bottom of the Encel Gorge.
557.100 / 110.550 / 1700 — Commune d’Evionnaz Développement 1455 m. — Dénivelé +103 m.
1 ©Spéléo Club du Nord Vaudois (SCNV), 2003
The main springs in the Encel zone have an annual average output of 300 litres per second. Most of the springs are fed by localized runoff, with the notable exception of the Fontaine Blanche and Petite Fontaine springs. Water from these two springs does not come exclusively from their immediate zone ; they are likely fed by secondary runoff water from the Salanfe area, or a perhaps by mixture of the two.
TRACER TESTS (6) The Susanfe Valley tracer tests were carried out between 1996 and 1998. Fluorescent dye was injected into a sinkhole near the intake of the western Sauflaz and into a fissure found along the trail to the Susanfe Hut. Both times the dye reappeared in the Green Spring (4). Additional tracer tests were carried out in 2013 in the Susanfe chasm. The dye reappeared in nine different springs within the Bonavau-Encel zone.
Springs showing positive for fluorescent tracer Hydrogeological relationship Fluorescent tracer injection points Educational Trail
0
250
500
1000 Mètres
Refuge de Bonavau
Réseau de Fontaine Blanche
1
Fontaine blanche
These tests also determined flow speeds : 120 to 150 metres per hour for the southern slope waters, as compared to 15-30 m/h for the northern waters, which pass through less permeable rocks.
Grande Source
Sources de la Cascade Source Verte
Grotte de Grande Source
Grotte de la Cascade Cabane de Susanfe
Gouffre de Salanfe
*Bonavau : from «bounavou» in local dialect, meaning «beautiful valley»
0
4
125
250
500 Mètres
© Eric Dupont
2
3 © Pierre-Yves Thevoz
© Pierre-Yves Thevoz
1
Cartographical representation of the Fontaine Blanche underground network.
2+3
Photos of the Fontaine Blanche underground network.
4
Left, the Waterfall Spring ; middle, the Sauflaz River ; right, the Green Spring.
5
Right, the Sauflaz Waterfall ; middle, the Fontaine Blanche overflow.
Main Spring
6
Tracer Tests carried out between 1996 and 1998 (J. Sesiano, 2004) and in 2013 (D. Cardis, 2014).
7
Speleologists have identified 49 cavities in the Susanfe Valley for a cumulative network of over 6 km (SSS, 2013). Main cavities are shown in this figure, which also includes the springs in the Bonavau Cirque.
The goal of a hike is not to save time, but to kill time gracefully. David Le Breton
Primary underground networks
Français English Deutsch passerelle-belle-etoile.ch
The Sauflaz River
Educational Trail
Études hydrologiques et géologiques Françoisxaviermarquis sàrl Design spirale.li Impression Avanthay Sérigraphie
7