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Institut für Wasser- und Umweltsystemmodellierung - IWS



"Development of Ecological oriented Flow Regimes based on Habitat "

In eco-hydraulic investigations biological, morphological, and hydrological or hydraulic parameters are linked and evaluated with respect to river habitats. Habitat modelling as a suitable tool to bridge the gap between physical and biological parameters has been used successfully in eco-hydraulic projects for several years. Presently, in fish habitat simulations normally the basic hydromorphological parameters "flow velocity", "water depth", and "dominant substrate" are linked with habitat requirements of chosen indicator-organisms. However, the alteration of morphology and its effects on hydraulics are usually not well considered in most cases the habitat simulations are based on steady state morphological conditions and do not take into account any dynamic processes.

Due to the fact that natural morphological conditions in most rivers are severely affected by river regulation works, changed flow regime, in particular as a consequence of hydropower use and land use, the consideration of modified morphological processes within the assessment of river habitats is essential.

Exemplified by case studies the procedure how morphodynamic aspects are implemented in the habitat modelling process with the model CASiMiR is presented. The emphasis lies on gravel spawning fish species with their need of definite substrate conditions such as accessibility of the interstitial zone that might be blocked by embeddedness or armoring layer. Seasonal requirements for fish in particular during spawning and rearing phase are regarded as well. The application of habitat modelling considering important morphological processes forms an upgraded basis for decision support in the framework of river management issues and for the development of optimized mitigation measures.