Exploring Geological and Topographical Controls on Low Flows with Hydrogeological Models
Claire Carlier, Stefanie Wirth, Fabien Cochand, Daniel Hunkeler & Philip Brunner
| Abstract |
This study investigates how catchment properties influence low-flow
dynamics. With 496 synthetic models composed of a bedrock and an
alluvial aquifer, we systematically assess the impact of the
hydraulic conductivity of both lithologies, of the hillslope and of
the river slope on catchment dynamics. The physically based
hydrogeological simulator HydroGeoSphere is employed, which allows
obtaining a range of low-flow indicators. The hydraulic
conductivity of the bedrock K bedrock , a proxy for transmissivity,
is the only catchment property exerting an overall control on low
flows and explains 60% of the variance of Q95/Q50. The difference
in dynamics of catchments with same K bedrock depends on hillslope
gradients and the alluvial aquifer properties. The buffering
capacity of the bedrock is mainly related to K bedrock and the
hillslope gradient. We thus propose the dimensionless bedrock
productivity index (BPI) that combines these characteristics with
the mean net precipitation. For bedrock only models, the BPI
explains 82% of the variance of the ratio of Q95 to mean net
precipitation. The alluvial aquifer can significantly influence low
flows when the bedrock productivity is limited. Although our
synthetic catchment setup is simple, it is far more complex than
the available analytical approaches or conceptual hydrological
models. The direct application of the results to existing
catchments requires nevertheless careful consideration of the local
geological topographic and climatic conditions. This study provides
quantitative insight into the complex interrelations between
geology, topography and low-flow dynamics and challenges previous
studies which neglect or oversimplify geological characteristics in
the assessment of low flows. © 2018, National Ground Water
Association. |
| Keywords |
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| Citation | Carlier, C., Wirth, S., Cochand, F., Hunkeler, D., & Brunner, P. (2019). Exploring Geological and Topographical Controls on Low Flows with Hydrogeological Models. Groundwater, 57(1), 48-62. |
| Type | Journal article (English) |
| Date of appearance | 1-2019 |
| Journal | Groundwater |
| Volume | 57 |
| Issue | 1 |
| Pages | 48-62 |
| URL | https://doi.org/10.1111/gwat.12845 |