River sedimentation / Речное осадконакопление

Worldwide the majority of water bodies (rivers, reservoirs and lakes) are no longer in a natural morphodynamic status due to anthropogenic interventions in the catchment area as well as in the river itself. Alterations in the catchment, e.g. uprooting, may lead to high sediment intrusions in river systems even during relatively short precipitation events. The effect of high suspended load concentration and the intrusion of fine sediments (clogging) result in a reduction of habitat quality for many aquatic species. Furthermore, the low water quality can negatively affect both macroinvertebrates as well as microbial organisms on the sediment bed due to increased turbidity as well as sediment smothering that alter the light climate and oxygen penetration, respectively. Thus, in the long term, fine material intrusion also provokes a reduction of biodiversity. Consequently, rivers lose their capability to provide several ecosystem functions and services. Additionally, river modifications due to hydraulic engineering disturb the sediment continuity and natural sediment transport dynamics. The construction of dams and reservoirs, e.g. for drinking water purposes, flood mitigation or energy production results worldwide in a reduction of sediment availability in rivers of 20 × 109 ty−1. This discontinuity reduces the storage potential of the reservoirs and thus causes economic losses but also impairs the whole aquatic ecosystem sustainably. As a result, ongoing river bed erosion downstream of dams and thus so called ‘hungry rivers’ can be observed which coincide mostly with a reduction of the groundwater level and with local bank erosion and bridge foundation scour. From an ecological perspective, the uncontrolled and diffusive inflow of nutrients and pollutants into rivers also changes the environmental conditions and severely impacts the natural system. For instance, an additional input of nutrients and phosphate might stimulate the growth of cyanobacteria and increase the secretion of harmful toxins. As a consequence affected rivers and lakes can no longer provide drinking or irrigation water or serve for recreation purposes. <...>