Assessment of river alteration using a new hydromorphological index.

Main river systems in large watersheds are mostly destroyed due to intense human activities. These rivers are modified by a number of water infrastructures such as dams, diversion weirs, flood control structures, and sediment traps. Such modifications alter the hydrology, continuity, and habitat quality of river waterbodies and degrade their overall ecological status. This study provides a systematic and quantitative assessment of river hydromorphology with a composite index based on four sets of criteria (i.e., hydrology, channel continuity, habitat quality, and bed modification) to assess the level of human intervention. The developed index is tested and implemented in Gediz River Basin in Western Anatolia (Turkey), which is one of the most important watersheds with regard to human settlements as well as agricultural and industrial production. The results of the developed index have revealed values between 42.36 and 88.14 on a 0-100 scale and a gradual decline in overall river hydromorphological quality along the flow path. The analysis has shown that barrier effects were found to be crucial in reduced river continuity and bed modification for flood control has resulted in degraded instream and riverbank habitat quality. The developed index methodology can serve as a systematic tool for assessing the hydromorphology and its associated influence in the ecological status of rivers. It can further assist the decision-makers in planning and prioritizing river restoration projects.

A first attempt at a holistic analysis of various influencing factors on the fish fauna in the Eastern European Alps.

Fish are some of the most threatened vertebrates in the world due to their often-sensitive response to environmental changes. Major land-use changes in the European Alps have direct and indirect impacts on fish communities, and these impacts are expected to increase in the future. Therefore, the identification of factors that are associated with the distribution of fish communities is of great importance to develop guidelines for management, precautions and sustainable use of running waters. In this study, the relationship of various factors - landscape structure and land use, topography, morphology, hydrology, physical and chemical water characteristics, hormonally active substances, pesticides, food availability, fisheries and piscivores birds - with fish assemblages are analysed. Field data from 81 stream sections from 2001 metres above sea level (m.a.s.l.) down to 219 m.a.s.l. are used in the study. The results reveal that the number of fish species has a strong association with topographic characteristics in the catchment area as well as with landscape configuration. Fish abundance and biomass are associated mostly with land-use type, hydrology, morphology as well as topography. In addition, there are indirect connections between fish abundance and biomass through land-use type, topography, water properties and hydromorphology. The results clearly indicate that not a single factor, but a multitude of factors are associated with the fish communities in the Eastern European Alps.