Author(s): Sebastian Schwindt; Maximilian Kunz; Silke Wieprecht; Shanghong Zhang; Jin Zhang; Caihong Tang; Le Wang
Linked Author(s): Silke Wieprecht, Sebastian Schwindt
Keywords: No keywords
Abstract: Anthropological development fragmented many river ecosystems and disrupted their connectivity. Affected river landscapes changed from natural fluvial landforms with a high degree of biodiversity into monotonous streams. In addition, many rivers are longitudinally divided by dams and laterally confined by hydraulic structures (e.g., for bank protection or water diversion). The expected hydro-climatic change will additionally impinge on the runoff regime of many rivers and further increase the stress on aquatic ecosystems. Since pristine river ecosystems are vital for the global food chain (e.g., as a habitat for many microorganisms) and provide resilience against natural disasters (e.g., floods and droughts), river restoration has become a primary action to prevent climate change impacts. This is why thousands of river restoration projects are currently in progress worldwide though the scientific baseline is disappointing and a transfer of knowledge from project-external findings is often lacking. For this reason, in a new Sino-German study, we are identifying new parameters for assessing lateral, vertical, and longitudinal connectivity of rivers and how combined connectivity affects ecosystem quality. While lateral and longitudinal connectivity as well as their interactions have already been extensively studied, vertical connectivity between rivers and their hyporheic zones is rarely considered as an integral element for ecosystem functioning. Furthermore, we analyze the link between three-dimensional (lateral, longitudinal, and vertical) connectivity and ecological assessment criteria, such as the Habitat Suitability Index. The Yellow River in China and the German Middle Rhine serve as testbeds and merging the findings from both sites will finally enable a transfer of results and vetting of hypotheses for two river ecosystems. This choice was made because the ecosystems of the Yellow River in China and the Rhine in Germany emblematically testify to the evolution of ecosystem degradation that came along with industrialization in the last two centuries. The here presented component of our study focuses on the Rhine, where we combine lateral connectivity parameters with vertical profile characteristics of parameters such as hydraulic conductivity or oxygen concentration. To this end, we conduct intensive fieldwork in which we sample grain sizes at and underneath the surface of alluvial plains. For instance, we use a freeze core technique in combination with structure from motion to derive a digital twin of the in-situ sediment matrix. Ultimately, at the end of this study, we want to establish a globally applicable scientific foundation to holistically assess and improve ecosystem connectivity.