Frequently, single measurement devices are placed at the river bank, which are easy to access.

However, not only standards in the allowance of SSC are lacking, urgently needed methodological standards are missing regarding how fine sediment concentrations (SCC) are measured/monitored to evaluate the magnitude of the ecological impact. In addition, specific circumstances with respect to the predominant fish species and other biological indicators need to be considered. non-glacial catchment) including the natural variability of the SSC. However, site and catchment-specific values need to be identified (e.g., glacial catchment vs.

For instance, at the Rhone river in France, a threshold for a permanent concentration of 5.0 g L −1 was established and for the river Mur in Austria, 4.5 g L −1, respectively. In different case studies, various limitations to avoid negative impacts on the ecology regarding SSC during reservoir flushing became apparent. High fine sediment loads in the water column were identified as one of the main pressures on aquatic ecology linked with reservoir flushing e.g. Despite criticism on the comparatively small sample sizes and the bias of fine sediment quantities due to larger sediments in the sample, freeze-coring was established as a standard procedure to quantify FSI.

Īs already stated, a method to determine FSI is freeze-coring, which was developed to achieve volumetric samples of bed sediments. As target species, macroinvertebrates and fish are used in the case of fish, the most sensitive periods are during egg-development phase and early larval stage. Moreover, suspended sediment concentration (SSC) have, besides the already above mentioned negative influences, been highlighted as one of the central parameters, where the environmental assessment shows clear responses of aquatic organisms. A frequently applied assessment tool is freeze-coring (FC), developed to gain information of the Fine Sediment Infiltration (FSI) not only close to the surface but also in the subsurface layer compare to. For evaluating changes of the abiotic environment, measurements of fine sediment infiltration (FSI) and the documentation of the fine sediment infiltration rate are state-of-the-art. Different abiotic and biotic parameters are used to document possible impacts on a local scale. Monitoring strategies are mostly based on the Before-After-Control-Impact (BACI) approach. Especially, the increased fine sediment loads, which may follow controlled reservoir drawdowns or reservoir flushing, were investigated on a local scale e.g. In contrast to reach scale assessment (compare to ), local scale studies in terms of sediment management for controlled drawdowns or reservoir flushings were more frequently applied. In order to get better insight into possible negative impacts, in principle reach as well as at a local scale, aspects should be studied. In the long term, also changes on the downstream morphology, sediment quality and sediment quantity may influence the habitat quality permanently. However, all these mentioned impacts happen during a limited period. More recently, sediment management actions in terms of preserving storage volume of reservoirs (e.g., mainly for energy production) were studied, which may result in additional negative impacts on aquatic organisms, like reduced macroinvertebrate communities, hypoxia of fish and mechanical damage of fish (like gills).

Negative impacts on reproduction, growth and total biomass through different operation schemes like hydropeaking an interruption of migration corridors through weirs or a flow abstraction are documented and also combined effects need to be considered. The construction of hydropower plants and their operation affects the aquatic ecology on various scales.

Minbox review 2015