Showing papers in "River Systems in 2012"

Nitrogen dynamics in complex Danube River floodplain systems: effects of restoration

Abstract: We used a hydromorphological model to assess areas of potential high denitrification rates and nitrous oxide release in a frequently and an infrequently connected fl oodplain system of the Danube River under different river discharge conditions. Based on the model’s projections, the decoupled floodplain was predicted to have more areas of high potential denitrification during mean and elevated discharge, but with more sites dominated by incomplete denitrification, resulting in higher N2O emission. In the restored floodplain, frequently inundated, the model predicted that lower rates of denitrification would occur at lower river discharge levels, dominated by complete denitrification, resulting in N2rather than N2O production. During an annual flood (5300 m3s–1), flooding both floodplains, the restored floodplain was predicted to have more areas of high potential denitrification activity than the decoupled floodplain. The model outputs suggest that floodplains subject to frequent inundations can effectively and efficiently use nitrate input from the main river channel, resulting in complete denitrification. Restoration measures should attempt to promote frequent inundation periods in order to fully realize the high denitrification potential of floodplain systems.

The role of reference conditions in water quality assessment: application of a fuzzy logic-based Decision Support System (DSS) in the Danube and Elbe River Basins

Abstract: The recent defi nition and submission of WFD-compliant River Basin Management Plans required large efforts of water managers and highlighted a number of data, knowledge and methodological gaps that need to be fulfi lled during the next management cycle. The complexity of the WFD implementation process calls for easy-touse, reliable and scientifi cally sound decision support tools that consider relevant aspects of the basin of concern. For this purpose, a Decision Support System (DSS) for risk-based assessment and management of river basins was developed within the EU MODELKEY project. The MODELKEY DSS allows assessing the chemical and ecological status of water bodies by applying both the One-Out All-Out principle, suggested by the WFD, and a novel Integrated Risk Assessment (IRA) methodology, developed within the project. In this paper, main results obtained by DSS application to two large European rivers, i.e. Elbe and Danube, are presented and discussed, based on a set of biological, chemical and physico-chemical indicators, which have been evaluated in relation to available reference conditions. The WFD ecological and chemical status assessment as well as analysis of intermediate results was strongly affected by the methods used to derive reference conditions, the applied indicators, and the methods used to aggregate indicators results. Minimally disturbed conditions (MDC) are the best choice as reference conditions, being characterized by generally high index values (good status) for all biological indices. Where MDC are not available, historical conditions could be a good substitute; they should be preferred to least disturbed sites (in particular when the river is generally impaired as the Danube River).