Nationalparks Austria NPA
Eintrag Nr. 29394
Hydrological connectivity between surface and subsurface systems in riverine floodplanes - a key factor in controlling groundwater nutrientt dynamics and the structure of hypogean animal assemblages.
Diplomarbeit an der Universitšt Wien - Hydrological connectivity between surface and subsurface systems in riverine floodplanes - a key factor in controlling groundwater nutrientt dynamics and the structure of hypogean animal assemblages.
In the presented study three factor could be delineated which effect nitrate concentrations in groundwater of alluvial floodplains: (i) surface water groundwater interactions, (ii) residence times of groundwater and (iii) interaction of groundwater with the unsaturated zone at rising and falling groundwater levels and/or surface water infiltration via the forest soil/root system at flood events. For the Regelsbrunn floodplain segment it could be demonstrated that the degree of hydrological connectivity between surface water and groundwater is highly heterogeneous in space and time. Spatially connectivity between the surface and subsurface aquatic systems tends to decrease from the river towards the fringe of the floodplain. However, the main factors determining exchange processes between surface water and groundwater are the permeability of infiltration channel beds and banks and the geomorphology (meanders and bends) of the main river and the backwater system. Heterogeneity of connectivity in time is a result of the hydrological dynamics of the surface water system. N-NO3- concentrations in deep groundwater are closely linked to the connectivity between surface water and groundwater and residence times of water in the subsurface. N-NO3- concentrations in shallow groundwater are additionally influenced by contact of groundwater with the soil/root system due to fluctuations of the groundwater table. High nitrate concentrations are released from the forest soil during flood events. However, the riparian forest soil/root system acts as a filter and hence nitrate is hardly transmitted to deeper groundwater layers. Generally the investigated alluvial aquifers had a purifying effect on surface water passing through the subsurface system regarding N-NO3- concentrations. P-PO43- retention is mainly dependent on residence time of water in the subsurface and the proportion of fine sediment in the alluvial deposits. N-NH4+ levels in groundwater are generally low, probably due to sorption processes and nitrification under oxic conditions. The results on groundwater crustaceans support the view that subsurface species diversity and animal assemblages are closely linked to system hydrology which influences variables like physical habitat stability and oxygen and probably organic carbon availability. Flood events have different effects on animal assemblages depending in the degree of subsurface habitat stability and location of the site in relation to surface water channels. During a severe summer flood animals were flushed downward into deeper groundwater layers at sites distant to surface channel. There physical habitat stability is high and repopulation of shallow groundwater after flood disturbance is quick. Close to surface channels, where surface water/groundwater interactions are higher and physical habitat stability is lower, animals ate flushed out from the interstices and repopulation occurs from neighbouring habitats.
Diplomarbeit Steininger; Hydrological connectivity between surface and subsurface systems in riverine floodplanes - a key factor in controlling groundwater nutrientt dynamics and the structure of hypogean animal assemblages.