MOSES
Hydrologische Extreme

The event chain "Hydrological Extremes" within MOSES investigates the effects of climate change induced extreme conditions on long term trends in earth ecosystems. According to recent predictions, the frequency and intensity of droughts and flood events in Europe change. While in the western European area, the drought frequency and intensity will increase, in the more eastern areas parts of Europe, the floods situations will potentially become more frequent and intense. It is not yet understood how these expected changes affect ecosystems on a long term run. The overall goal of MOSES Hydrological Events aims to develop and provide high-level mobile and modular infrastructure to measure and analyze event like deviations in the earth system within the BMBF research area Earth & Environment.

A functional understandig of event like hydrological extremes on the earth system affects not only a single earth compartment but is highly cross-compartimental. Even though the effects of such events in different compartments along the river-to-coast stretch may be different, it is indispensable to achieve a functional understandig across the earth compartments because effects of extremes act sequential from the atmosphere where extremes are initiated via the terrestrial and freshwater environment towards the coastal marine environment.

From the methological point of view, the scientific-observatorial approach starts with the measurement of changes in the precipitation rate potentially leading to draught or flood situations. It continues with the increased retention or mobilization of solutes (organic carbon, nutrients, pollutants) depending on the aquifer status from forest and agricultural soils and urban areas. Further, it investigates the changes in the microbial production and degradation of the solutes on the way to the sea as well as the effects of this climatic extremes to the tropic cascade along the catchment area. In the coastal regions, the amount of water entering the estuaries significantly affect the marine ecosystem. Depending if water coming from the river catchment is exceptionally sparse or in surplus, the coastal ecosystem reacts with accordingly with either increased eutrophication and pollution when nutrients and other pollutants are in surplus or with changes in the water chemistry including climatic relevant gases like methane and pCO2. The functional understanding of such changes to the water chemistry and the tropic cascade in the source area of a hydrological event, along its transition pathway in the terrestrial and limnic compartment as well as in the coastal marine environment is detrimental for the ecological understanding of its relevance in the earth system. Only the simultaneous consideration of all these elements of the event chain by different Helmholtz centres may provide a comprehensive understanding of hydrological extremes and their consequences for freshwater and marine environments. This enables to estimate their relevance for these environments and provides a basis for potential management options.

In particular, the overarching goal is to connect the water bodies of the River Elbe through the tidal river with the North Sea taking into account the different residence times with the aim to fill the existing knowledge gaps concerning these research questions:

- Is there a measurable impact on coastal zones due to the changing export of nutrients, e.g. during low water periods?
- Is there a measurable impact on coastal zones due to changing DOM composition?
- Can we detect significant changes in CO2 und CH4 emissions along the rivers and in coastal zones depending on the hydrological extreme events?
- Are there changes in micro pollutant discharge into coastal zones due to different hydrological extremes?