TU Berlin

Urban Water InterfacesInitial project plan_N6

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Initial project plan

State of the art and preliminary work

The transition zone between surface water and groundwater (the so-called hyporheic zone, hz) can be regarded as a hydrologically driven bioreactor affecting transport, exchange and retention of water, nutrients and heat. The dynamic system has many important functions as habitat and refuge with regard to nutrient cycling, attenuation of contaminants and the general functioning of linked surface water-groundwater ecosystems (Brunke & Gonser 1997, Krause et al. 2011). Anthropogenically impacted urban freshwater systems differ significantly from pristine systems where most studies of hz research have been conducted so far. Due to altered water quality and sediment properties in urban freshwater systems, the aforementioned functions might be heavily modified. The biogeochemical functions of the hz of urban waters become important especially for planning of restoration measures because mechanisms, such as transfer, retention and degradation of chemical compounds in this zone, are poorly understood and have up to now not been considered during restoration (Hester & Gooseff 2010). Considering the current state of hz research, there is a great lack of knowledge on transient exchange between surface and groundwater in urban waters, especially with respect to biogeochemical processing and the fate of micropollutants (Nützmann et al. 2011, Lewandowski et al. 2011a).

Aims and work steps

This doctoral thesis aims to understand the closely coupled hydrological and biogeochemical processes in the hz of urban streams (mechanisms), to develop and improve measurement techniques for hydrological and biogeochemical processes at groundwater-surface water interfaces which can cope with the characteristics and challenges of urban freshwaters (methods), to evaluate the role and ecosystem service of the hz in anthropogenically impacted, heavily modified freshwater systems (functions) and to study the impacts of restoration measures on the attenuation of chemical compounds in the hz (applications). The streams Erpe and Panke are chosen as examples. Both are impacted by treated wastewater and in addition, the urban section of the Panke is currently restored which will take several years. Thus, we have two typical urban streams with typical pollution scenarios, but they are quite different in their morphometric structures and longitudinal gradients. To investigate the hydrological processes in the hz, the PhD student will rely on different heat measurement methods: distributed temperature sensing (Blume et al. 2013), heat-pulse sensors (Lewandowski et al. 2011b) and temperature depth profiles (Meinikmann et al. 2013). Exchange rates, retention times and flow paths are the basis for the understanding of the biogeochemistry and for the modelling of hyporheic zone processes. Biogeochemical sampling will be conducted in the hyporheic zone along flow paths which were previously identified with multi-level samplers, mini-piezometers, Rhizon-samplers, 2D-dialysis samplers (Lewandowski et al. 2002), and gel-samplers (Davison et al. 1991). The turnover in the hz of the different streams and at different sites / structural elements of both streams will be quantified. Subsequently, the hydrological exchange pattern determined on large spatial scales will be used for the upscaling of local findings (e.g. by distributed temperature sensing or airborne thermal infrared radiation, Lewandowski et al. 2013). Furthermore, biogeochemistry will be studied on larger scales (e.g. by Lagrangian sampling) as an additional basis for upscaling. The combined knowledge of both hydrological and biogeochemical processes will be used to evaluate the overall role of the hz in urban freshwater systems and to develop a conceptual model of the most relevant processes and their interactions. Finally, measures to improve the effectivity of hyporheic reactors and thus to strengthen ecosystem services will be suggested.

Connections to interfaces and other doctoral theses

N6 will be carried out in very close collaboration with N7 which uses data and insights from N6 for modelling; vice versa, modelling results and modelling demands will inspire further investigations of N6. N1 and N6 study similar processes at the same field sites but on different spatial scales. While N1 focuses on biofilms, N6 focuses on the hyporheic zone which is several decimetres thick. Further, there are linkages to N3, N5 and T4 on the sediment-water interface and to T5 on adsorption/desorption. 

 

References

Blume, T.; Krause, S.; Meinikmann, K. and Lewandowski, J. (2013). Upscaling lacustrine groundwater discharge rates by fiber-optic distributed temperature sensing. Water Resources Research 49, 1-16, DOI:10.1002/2012WR013215

Brunke,M. & Gonser,T. (1997): The ecological significance of exchange processes between rivers and groundwater. Freshwater Biology, 37, 1-33

Davison,W., Grime,G.W., Morgan,J.A.W. & Clarke,K. (1991: Distribution of dissolved iron in sediment pore waters at submillimetre resolution. Nature 352, 323-325

Hester,E.T. & Gooseff,M.N. (2010): Moving beyond the banks: hyporheic restoration is fundamental to restoring ecological services and functions of streams. Environmental Sciences and Technology 44, 1521-1525

Krause,S., Hannah,D.M., Fleckenstein,J.H., Heppell,C.M., Kaeser,D., Pickup,R., Pinay,G., Robertson,A.L. & Wood,P.J. (2011): Inter-disciplinary perspectives on processes in the hyporheic zone. Ecohydrology 4, 481-499

Lewandowski,J., Meinikmann,K., Ruhtz,T., Pöschke,F. & Kirillin,G. (2013): Localization of lacustrine groundwater discharge (LGD) by airborne measurement of thermal infrared radiation. Remote Sensing of Environment 138, 119-125

Lewandowski,J., Putschew,A., Schwesig,D., Neumann,C. & Radke,M. (2011a): Fate of organic micropollutants in the hyporheic zone of a eutrophic lowland stream: Results of a preliminary field study. Sci. Total Environ. 409, 1824-1835

Lewandowski,J., Angermann,L., Nützmann,G. & Fleckenstein,J. (2011b): A heat pulse technique for the determination of small-scale flow directions and flow velocities in the hyporheic zone of sand bed streams and other sand beds. Hydrological Processes, 25, 3244-3255

Lewandowski,J., Rüter,K. & Hupfer,M. (2002): Two-dimensional small-scale variability of pore water phosphate in freshwater lakes: Results from a novel dialysis sampler. Environmental Science & Technology 36, 2039-2047

Meinikmann,K., Nützmann,G. & Lewandowski,J. (2013): Lacustrine groundwater discharge: Combined determination of volumes and spatial patterns. Journal of Hydrology 502, 202-211

Nützmann,G., Wiegand,C., Contardo-Jara,V., Hamann,E., Burmester,V. & Gerstenberg,K. (2011): Contamination of urban surface and ground water resources and impact on aquatic species. In: Endlicher,W. et al. (2011). Perspectives in Urban Ecology. Springer Heidelberg, 43-88

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