Author(s): Matthias Schneider; Ianina Kopecki; Andreas Eisner; Markus Noack

Linked Author(s): Matthias Schneider, Markus Noack

Keywords: Habitat; Model; Sediment; Embeddedness; Fish; Spawning; CASiMiR

Abstract: Among the tools to analyze, assess and quantify the impacts of human activities on ecological functions in river systems aquatic habitat simulation models have gained a key role. Such models have been applied for almost thirty years, but their initial use focussed on instream flow assessment, particularly minimum flow problems. In the meantime their range of application has grown significantly. Today, models contribute to simulation-based decision making in water resources management, including instream flow regulations, ecological reservoir releases, river restoration efforts and various types of river engineering projects. Currently, state-of-the-art habitat modeling is restricted to the investigation of discharge or morphology scenarios for steady state conditions, although transient, dynamic processes play a crucial role for many aquatic organisms. Particularly the requirements of gravel-spawning fish species reproduction are closely related to the temporal and spatial variability of the substrate layer and the accessibility of the interstitial zone. The habitat model CASiMiR developed at the Institute of Hydraulic Engineering of the Universitaet Stuttgart enables a flexible fuzzy-logic, expert knowledge-based linkage between abiotic hydro-morphological conditions in rivers and biotic requirements of aquatic organisms. Within the frame of the Interreg IIIB-Project „ ALPRESERV “the model was used to address the effects of the degraded sediment regime downstream of a reservoir in river Mur (Austria) on spawning habitats of European Grayling (Thymallus thymallus). A modified sediment regime is a major problem in many rivers downstream of alpine and sub-alpine reservoirs. The retention of coarse sediments during long periods of the year on one hand and the increased introduction of fine sediments during flushing events on the other often lead to a heavily modified river bottom morphology affected river stretches. Particularly embedding effects and the development of armoured layers strongly impact the usability of river bottom as habitat. This paper presents an approach to incorporate morphodynamic aspects into the habitat simulation process. Based on an extended description of river bottom substratum the suitability of habitats for two different scenarios of morphology, including river engineering measures were investigated. First results indicate that the consideration of morphodynamics is essential for the assessment of riverine habitats and key factor for the particular important reproduction habitats for fish. The incorporation of dynamic aspects expands the range of application for habitat modeling as a decision support tool in river management.

DOI:

Year: 2007