Improving understanding of groundwater flow in an alpine karst system by reconstructing its geologic history using conduit network model ensembles

Reconstructing the geologic history of a karst area
can advance understanding of the system’s present-day hy-
drogeologic functioning and help predict the location of un-
explored conduits. This study tests competing hypotheses
describing past conditions controlling cave formation in an
alpine karst catchment, by comparing an ensemble of mod-
eled networks to the observed network map. The catch-
ment, the Gottesacker karst system (Germany and Austria),
is drained by three major springs and a paleo-spring and in-
cludes the partially explored Hölloch cave, which consists
of an active section whose formation is well-understood and
an inactive section whose formation is the subject of debate.
Two hypotheses for the formation of the inactive section are
the following: (1) glaciation obscured the three present-day
springs, leaving only the paleo-spring, or (2) the lowest of
the three major springs (Sägebach) is comparatively young,
so its subcatchment previously drained to the paleo-spring.
These hypotheses were tested using the pyKasso Python li-
brary (built on anisotropic fast-marching methods) to gener-
ate two ensembles of networks, one representing each sce-
... mehr
nario. Each ensemble was then compared to the known cave
map. The simulated networks generated under hypothesis 2
match the observed cave map more closely than those gener-
ated under hypothesis 1. This supports the conclusion that the
Sägebach spring is young, and it suggests that the cave likely
continues southwards. Finally, this study extends the appli-
cability of model ensemble methods from situations where
the geologic setting is known but the network is unknown to
situations where the network is known but the geologic evo-
lution is not.
1 Introduction