Einfluss periglazialer Deckschichten auf Abflusssteuerung am Beispiel des anthropogen überprägten Wüstebaches (Nationalpark Eifel)

  • Impact of pleistocene cover-beds on discharge : the anthropogenic influenced Wüstebach-River (Nationalpark Eifel) as an example

Borchardt, Holger; Lehmkuhl, Frank (Thesis advisor)

Aachen : Publikationsserver der RWTH Aachen University (2013)
Dissertation / PhD Thesis

Aachen, Techn. Hochsch., Diss., 2012

Abstract

Pericglacial cover-beds are widespread in Central European subdued mountains. Structure, texture, and thickness of these pleistocene gelifluctional slope deposits are important factors concerning pedogenesis, metabolism as well as infiltration, interflow, ground water renewal, and discharge. These cover-beds can be divided in two to three different layers. The upper layer is characterized by a low bulk density and consists of a mixture of local debris and loess. The lowermost layer consists of local debris, in this case mainly clay. In some regions a third layer in-between has been observed, but this intermediate layer was not detected in the catchment of the Wüstebach. During rainfall events, the upper layer enables water to infiltrate relative fast, thus increasing soil moisture. Due to its higher density, the lower layer reduces vertical velocity of interflow and redirects the interflow to the next river. The lower layer reacts delayed but can serve as preferred flow path for already infiltrated water, thus affecting discharge. The Wüstebach-catchment was chosen to investigate whether this model can be adapted to this area as well or not. To answer this question, soil moisture, precipitation, and discharge were measured for a period of two years. Additional data concerning infiltration rate, density, penetration resistance, and conductivity were collected to analyse the spatial heterogeneity of hydrological parameters of the soils. Mapping of soils and a geomorphological mapping support the spatial distribution and structure of periglacial cover-beds. The results reveal a fast reaction of the upper layer and a delayed and less intense reaction of the lowermost layer during rainfall, especially in the summer season. High precipitation does not necessarily lead to high discharge. During the winter season, when soils are saturated, even small precipitation can lead to high discharge. Furthermore, snow can lead to a delayed flow at the beginning of spring when temperatures rise, thus affecting statistical results. Statistical analyses indicate a strong correlation between precipitation and discharge. However, relief and periglacial cover-beds of the Wüstebach-area do not seem to have a significant impact on discharge. The spatial heterogeneity of relevant hydrological parameters combined with water retention areas resulting in cascade effects as well as the strong human impact may lead to a less significant importance of cover-beds. The numerous parameters involved in natural processes, especially concerning precipitation and discharge, differ from region to region and seem to be too complex to be described by a general model.

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