 |
| Titel |
Spatial and temporal simulation of groundwater age distributions of a small mountainous catchment |
| VerfasserIn |
Anita Gundel, Markus Weiler, Mario Schirmer |
| Konferenz |
EGU General Assembly 2013
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250072253
|
|
|
|
|
|
| Zusammenfassung |
| The spatial and temporal storage characteristics of catchments are relevant to identify the
vulnerability of catchments to climate change. Areas with high mean groundwater ages imply
long residence times of water particles in the aquifer and are therefore a good indicator for
high storage capacity of a catchment. Groundwater age in general is strongly influenced by
porosity, flow direction and flow velocity. Hence, the great challenge for moutainous
catchments is the steep topography and the complex geology which has the greatest impact
on the groundwater age distribution. The main purpose of this study is the simulation of the
groundwater age of a well-instrumented pre-alpine catchment in time and space to identify
storage characteristics. One possibility to simulate groundwater age distributions in space and
time is the application of a numerical groundwater model, which takes into account
complex geological structures as well as the flow and transport processes of the
unsaturated and saturated zone. In our study, we used the numerical 3D-finite-element
groundwater flow and transport model FEFLOW with a transient direct mean age
simulation method based on a mass-weighted average age. The study catchment
Rietholzbach is located in the north-east of Switzerland, for which an adequate data set of
discharge, groundwater level, and isotopic composition of the groundwater and stream
water exists. First of all, a steady-state groundwater flow model was developed
to validate the stability and accuracy of the flow simulation and model structure.
Secondly, the steady-state results provide the initial conditions for the transient
flow and transport simulation of the groundwater age distribution. Residence time
simulations of this model were benchmarked against the stable isotope signal δ18O of
groundwater and discharge. The results show that less water is stored along the
creek in the shallow aquifer (young water) whereas substantial storage capacities
(old water) are available at the hillsides and in greater depths. The Rietholzbach
catchment has heterogeneous storage characteristics, strongly influenced by the
topography, with good storage capacities in the hillsides. The 3D direct simulation of
the mean groundwater age in combination with residence time simulation of an
environmental tracer provides reasonable results and is a useful approach to increase the
understanding of hydrological processes of a hydrogeological complex study site. |
|
|
|
|
|
|