Drinking water is an essential service provided by aquatic ecosystems that is increasingly threatened by human activities and climate change. Little is known about the impact of extreme weather events on freshwater due to their stochastic character. Yet, future scenarios project higher intensity and frequency of these events, intensifying uncertainty and challenges for water managers. Precipitation events boost the transport of dissolved organic matter (DOM) into lakes, impacting not only ecosystem processes but also the formation of non-desired carcinogenic disinfection by-products (DBPs) during drinking water disinfection. A spatially coordinated mesocosm experiment was designed in two Swedish lakes to study the impact of run-off variability on freshwater. To understand to what extent these effects differ with local climate and geography, standardized equipment and methods were applied at both sites. Three different pulse events (carbon and nutrient additions) were studied by varying their intensity and frequency to simulate extreme, intermediate, and continuous rainfall. Results confirmed that changes in concentration and composition of DOM were site-specific, were strongly dependent on run-off variability, and that the effect of pulses in input could be detected by monitoring proxies of DOM in the mesocosms. Also, DBP formation potential tests were performed, showing positive correlations with DOM proxies and sensitivity to pulse disturbances. These results can be used to support raw water management by developing, e.g., forecasting tools to control the formation of DBPs.

Primary Presenter: Angela Pedregal, Catalan Institute for Water Research (apedregal@icra.cat)

Authors:

Angela Pedregal-Montes, Catalan Institute for Water Research (ICRA)  (apedregal@icra.cat)

Eleanor Jennings, Dundalk Institute of Technology  (elanor.jennings@dkit.ie)

Rafael Marcé, Catalan Institute for Water Research (ICRA)  (rmarce@icra.cat)

Maria José Farré, Catalan Institute for Water Research (ICRA)  (mjfarre@icra.cat)