Lithological and tectonic control on groundwater contribution to stream discharge during low-flow conditions
Date issued
March 1, 2020
In
Water
Vol
12
No
2020
From page
821
To page
844
Reviewed by peer
1
Subjects
low flow groundwater geology permeability hydraulic conductivity lithology bedrock alluvial aquifer Molasse basin
Abstract
Knowing how stream discharge in an ungauged catchment reacts to dry spells is a
major challenge for managing water resources. The role of geology on these dynamics is poorly
understood. For the Swiss Molasse basin, we therefore explored how the geology influences the
groundwater contribution to stream flow during low-flow conditions. Using existing data from
geological reports and maps as well as from deep boreholes, we constructed a basin-wide overview
of the hydrogeological quality of the bedrock and investigated five catchments in 3D. We found that
catchments with the most permeable sedimentary bedrock are least sensitive to low flows (marine
sandstone, K = 10−4
to 10−5 m/s, Peff = 5–10%). In contrast, if bedrock K is low (K < 10−6 m/s),
the presence of a productive Quaternary volume becomes decisive for groundwater contribution
to stream flow. Limitations exist due to a restricted database for K and Peff values of the Molasse
and limited information on continuation of lithologies with depth. This emphasizes the need for
more hydrogeologically relevant data for the future management of water resources. Our results
highlighting what lithotypes favor groundwater contribution to stream flow are valid also in other
regions for the assessment of a catchment’s sensitivity to low flows
major challenge for managing water resources. The role of geology on these dynamics is poorly
understood. For the Swiss Molasse basin, we therefore explored how the geology influences the
groundwater contribution to stream flow during low-flow conditions. Using existing data from
geological reports and maps as well as from deep boreholes, we constructed a basin-wide overview
of the hydrogeological quality of the bedrock and investigated five catchments in 3D. We found that
catchments with the most permeable sedimentary bedrock are least sensitive to low flows (marine
sandstone, K = 10−4
to 10−5 m/s, Peff = 5–10%). In contrast, if bedrock K is low (K < 10−6 m/s),
the presence of a productive Quaternary volume becomes decisive for groundwater contribution
to stream flow. Limitations exist due to a restricted database for K and Peff values of the Molasse
and limited information on continuation of lithologies with depth. This emphasizes the need for
more hydrogeologically relevant data for the future management of water resources. Our results
highlighting what lithotypes favor groundwater contribution to stream flow are valid also in other
regions for the assessment of a catchment’s sensitivity to low flows
Publication type
journal article
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