Impacts of land use and cover change on water fluxes and soil functioning in Southern Brazil

The first objective of the PhD is to investigate structures of water fluxes at the landscape scale. Whether the structure or spatial distribution of water fluxes and water residence times in the system can be linkedto the spatial structure of biogeochemical processes or soil formation processes in the system will be a key question. At the landscape scale, non-invasive geophysical techniques can be used to characterize the structure of the subsurface that controls the water fluxes in the system. Wewill make surveys of the subsurface structure and derive the topographyof subsurface layers using methods like ground penetrating radar (GPR),electro magnetic induction (EMI) (Lavoue et al., 2010, Mester et al., 2011), and electrical resistivity tomography (ERT) (Vanderborght et al., 2013). In order to characterize lateral flow pathways and networks and monitor their appearance, we will use ERT. A comparison between observed networks and networks that are modeled based on a DEM of the impeding layers will be made. At the identified locations of subsurface flow paths,soil and water samples will be taken for biogeochemical analyses. A combination of structure information obtained with geophysical methods and time series of tracer concentrations (e.g. isotope tracers) in surface water provides crucial information that is needed to link process areas with process dynamics at these scales (Koch et al., 2009). The second objective is to simulate water fluxes (infiltration, lateral runoff and lateral subsurface groundwater and interflow) at specific times during the evolution or development of a landscape. The identified flux controlling structures will be used to set up a 3-D flow and transport model at the catchment scale. The PARFLOW model (Kollet and Maxwell, 2006) that describes 3-D variably saturated water flow, solute transport, soil-atmosphere interactions, and surface runoff will be used. The model is parallelized and tailored to massively parallel supercomputer architectures sothat it can be used to simulate water fluxes at landscape scale with a resolution that is required to resolve effect of structural features on flow and transport processes (Kollet et al., 2010). The PARFLOW simulations will be carried out using supercomputing infrastructures at the Forschungszentrum Jülich. The study will be carried out in cooperation with other partners in the SOGLO IUAP project. To investigate the impact of landuse on flow path structures and landscape development, two catchments in Brazil were selected by the project partners. The catchment differ in terms of land use with one of the catchments being deforestated andused for agriculture whereas the other is forrested.

Publication year:2019

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