Flusskorridore und Auenstrukturen im schweizerischen Mittelland (nördliches Alpenvorland) | River corridors and alluvial structures in Central Switzerland (northern sub-alpine area)
Long-term spatial variation of river channel distribution in this alluvial valley zone is described for two examples by analysing historical maps covering a period of over 300 years. Such a time series enables the identification of the occupied river corridor or «Pendelband». Two river sections in northern Switzerland were chosen, one of the Aare river and one of the Reuss river to analyse the spatial evolution of the river channels over time, as well as alluvial structures. Knowledge of the river corridor as an historical reference give us an important guideline when developing appropriate regional measures for river restoration projects.
RIVERINE LANDSCAPES: BIODIVERSITY PATTERNS, DISTURBANCE REGIMES, AND AQUATIC CONSERVATION
Abstract The term riverine landscape implies a holistic geomorphic perspective of the extensive interconnected series of biotopes and environmental gradients that, with their biotic communities, constitute fluvial systems. Natural disturbance regimes maintain multiple interactive pathways (connectivity) across the riverine landscape. Disturbance and environmental gradients, acting in concert, result in a positive feedback between connectivity and spatio-temporal heterogeneity that leads to the broadscale patterns and processes responsible for high levels of biodiversity. Anthropogenic impacts such as flow regulation, channelization, and bank stabilization, by (1) disrupting natural disturbance regimes, (2) truncating environmental gradients, and (3) severing interactive pathways, eliminate upstream-downstream linkages and isolate river channels from riparian/floodplain systems and contiguous groundwater aquifers. These alterations interfere with successional trajectories, habitat diversification, migratory pathways and other processes, thereby reducing biodiversity. Ecosystem management is necessary to maintain or restore biodiversity at a landscape scale. To be effective, conservation efforts should be based on a solid conceptual foundation and a holistic understanding of natural river ecosystems. Such background knowledge is necessary to re-establish environmental gradients, to reconnect interactive pathways, and to reconstitute some semblance of the natural dynamics responsible for high levels of biodiversity. The challenge for the future lies in protecting the ecological integrity and biodiversity of aquatic systems in the face of increasing pressures on our freshwater resources. This will require integrating sound scientific principles with management perspectives that recognize floodplains and groundwaters as integral components of rivers and that are based on sustaining, rather than suppressing, environmental heterogeneity.
Le transfert du mercure (Hg) utilisé comme descripteur du fonctionnement hydrologique (échanges cours d'eau - nappe) dans la plaine alluviale du Rhin supérieur : impact des aménagements
Des dosages de mercure (Hg) ont ete effectues dans des especes de mousses aquatiques (bryophytes), Fontinalis antipyretica Hedw., Cinclidotus danubicus Schiffn. & Baumg., Cinclidotus nigricans (Brid.) Wijk & Marg. et Amblystegium riparium Hedw., prelevees dans le reseau hydrographique de la plaine rhenane d'Alsace (Rhin canalise, son principal affluent l'Ill qui possede un champ d'inondation fonctionnel et dans le reseau des rivieres phreatiques). Le choix des points de prelevement a ete base sur les resultats obtenus lors des etudes anterieures utilisant les methodes des traceurs hydrologiques (Cl − ), et des analyses physico-chimiques de l'eau (NO 3 − , PO 4 3− , NH 4 + ) et la methode de bioindication de la qualite de l'eau basee sur les groupements vegetaux (...)