Intermittency of streams—a risk for water quality? | Austrocknung von Bächen – eine Gefahr für die Wasserqualität?
2019
Weigelhofer, Gabriele | Tritthart, Michael
Water scarcity is one of the greatest challenges for stream management in the 21st century. Already now, the majority of channel lengths of natural waterways are intermittent worldwide. Global warming will increasingly cause perennial streams to become intermittent also in temperate regions such as Austria. The project PURIFY (2018–21) aims at investigating the impacts of intermittency on the water quality and the self-purification capacity of streams in different regions in Austria. We want to identify factors, which significantly influence the resistance of in-stream processes towards desiccation. For this purpose, we sampled five perennial and five intermittent streams in Burgenland, Styria and Carinthia before and during the dry phase in 2018 to analyse the water quality and the activity of benthic microorganisms. Despite an extended dry period, we observed no significant differences in the microbial respiration, abundances, and enzymatic activities between perennial and intermittent reaches within the same region. We assume that dense shading by riparian trees and high accumulations of fine particles in the sediments helped to maintain a high humidity in the sediments and, thus, buffered the effects of drying on microbial processes. However, receding water levels in both intermittent and perennial reaches resulted in large fluctuations of nutrient concentrations. Extended field investigations combined with laboratory experiments and hydrodynamic modelling will clarify the short- and long-term effects of repeated drying on the microbial uptake of nutrients (self-purification capacity) and on the water quality in relation to stream type and degree of pollution.
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