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| Titel |
A tracer test to determine subsurface outflow of a karst catchment along the Lauchert-Graben, Swabian Alb |
| VerfasserIn |
Paul Knöll, Traugott Scheytt |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250149668
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| Publikation (Nr.) |
 EGU/EGU2017-14042.pdf |
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| Zusammenfassung |
| During a severe flood event in 2013 it was hypothesised that a significant amount of flood
water from the lower course of the Lauchert infiltrated into the karst system, flowing towards
the Danube catchment. The Lauchert, a tributary of the river Danube is a perennial stream in
the Swabian Alb, southern Germany. Its catchment is entirely comprised of Upper Jurassic
karstified carbonate rocks, slightly dipping south-east. The river mainly flows in the so called
Lauchert-Graben except for the lower course.
An artificial dye tracer experiment was conducted in August 2016 to examine a connection of
the Lauchert and Danube catchment. 4 kg of Uranine were injected into the unsaturated zone
of the Lauchert surface catchment, approximately 200 m west of the eastern main fault
of the Lauchert-Graben. Close to the injection point the Lauchert is crossing this
fault.
A total of 7 observation points were monitored, among those the river Lauchert and 6 springs
in the Danube valley. 3 of the springs were monitored with field fluorimeters while the other
observation points were monitored by regular sampling for 5 days. A tracer breakthrough was
detected at 3 springs in the Danube valley, showing a southward flow direction with a
maximum transport velocity of 81 m∕h. Tracer breakthrough curves were analysed using the
CXTFIT code implemented in Stanmod.
This experiment proved a preferential hydraulic connection from the Lauchert valley to
springs in the Danube valley in the vicinity of the Lauchert-Graben and revealed a flow
towards the Danube catchment. The monitored springs in the Danube valley are at least partly
fed by groundwater originating in the Lauchert catchment. Augmented flow of flood water
through the karst system becomes very likely if an inundation reaches outcropping karst
structures flanking the Lauchert flood plain. |
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