Aquifer configuration and geostructural links control the groundwater quality in thin-bedded carbonate–siliciclastic alternations of the Hainich CZE, central Germany
The quality of near-surface groundwater reservoirs is controlled, but also threatened, by manifold surface–subsurface interactions. Vulnerability studies typically evaluate the variable interplay of surface factors (land management, infiltration patterns) and subsurface factors (hydrostratigraph...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-12-01
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| Series: | Hydrology and Earth System Sciences |
| Online Access: | https://www.hydrol-earth-syst-sci.net/21/6091/2017/hess-21-6091-2017.pdf |
| Summary: | The quality of near-surface groundwater reservoirs is controlled,
but also threatened, by manifold surface–subsurface interactions.
Vulnerability studies typically evaluate the variable interplay of surface
factors (land management, infiltration patterns) and subsurface factors
(hydrostratigraphy, flow properties) in a thorough way, but disregard the
resulting groundwater quality. Conversely, hydrogeochemical case studies that
address the chemical evolution of groundwater often lack a comprehensive
analysis of the structural buildup. In this study, we aim to reconstruct the
actual spatial groundwater quality pattern from a synoptic analysis of the
hydrostratigraphy, lithostratigraphy, pedology and land use in the Hainich
Critical Zone Exploratory (Hainich CZE). This CZE represents a widely
distributed yet scarcely described setting of thin-bedded mixed
carbonate–siliciclastic strata in hillslope terrains. At the eastern Hainich
low-mountain hillslope, bedrock is mainly formed by alternated marine
sedimentary rocks of the Upper Muschelkalk (Middle Triassic) that partly host
productive groundwater resources. Spatial patterns of the groundwater quality
of a 5.4 km long well transect are derived by principal component analysis
and hierarchical cluster analysis. Aquifer stratigraphy and geostructural
links were deduced from lithological drill core analysis, mineralogical
analysis, geophysical borehole logs and mapping data. Maps of preferential
recharge zones and recharge potential were deduced from digital (soil)
mapping, soil survey data and field measurements of soil hydraulic
conductivities (<i>K</i><sub>s</sub>). By attributing spatially variable surface and
subsurface conditions, we were able to reconstruct groundwater quality
clusters that reflect the type of land management in their preferential
recharge areas, aquifer hydraulic conditions and cross-formational exchange
via caprock sinkholes or ascending flow. Generally, the aquifer configuration
(spatial arrangement of strata, valley incision/outcrops) and related
geostructural links (enhanced recharge areas, karst phenomena) control the
role of surface factors (input quality and locations) vs. subsurface factors
(water–rock interaction, cross-formational flow) for groundwater quality in
the multi-layered aquifer system. Our investigation reveals general
properties of alternating sequences in hillslope terrains that are prone to
forming multi-layered aquifer systems. This synoptic analysis is fundamental
and indispensable for a mechanistic understanding of ecological functioning,
sustainable resource management and protection. |
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| ISSN: | 1027-5606 1607-7938 |