Lake Aasee (Germany) – Analysis to understand the system of an extreme situation
The extreme weather conditions in 2018 had a direct effect on water bodies all over Germany. Low water discharges and the resulting extremely low water levels in combination with high temperatures led to critical situations in many flowing and standing waters. A particularly dramatic situation happened at Lake Aasee in Münster (Germany). On the morning of August 9th, 2018, suddenly a lot of fish died. The increasing number of extreme weather situations shows the need to develop adaptation processes for flowing waters, lakes and reservoirs. A full understanding of the system creates the necessary conditions to handle these challenges. In this context, flexible and high-resolution water body monitoring offers the collection of data for a full system understanding and improved water body management.
Shallow lake management in the face of climate change
After the extreme weather event in August 2018, the exact reason for the fish kill had to be clarified. The understanding of the process serves as a basis for developing future preventive and acute management actions. Theoretically, possible procedures like taking out sediment or aerating the lake must be tested for their effectiveness and economic efficiency. For this reason, the RiverView® team of the FiW analysed the sediment thickness with the help of an echo sounding analysis. They also analysed the potential of nutrient release under critical oxygen conditions. The sensor technology of the RiverView® system was combined with sediment analysis in the laboratory. The echosounder data includes points with spatial position and height values, which are used to create a digital terrain model, just like in a river bed study. Echo sounder use has also shown to be an efficient tool for river bathymetry (mapping of the river bed) in several flowing waters like the Niers and the Lippe (both rivers in Germany). This spatially highly accurate and still efficient data collection gives the essential data basis for the development of a numerical shallow lake model by the Research Institute for Ecosystem Analysis and Assessment at RWTH Aachen University (gaiac e. V.). The goal of the scenario analysis is to evaluate options for actions to avoid or overcome extreme situations similar to those in summer 2018.
Costumer: City of Münster
Partner on subcontract: Research Institute for Ecosystem Analysis and Assessment at RWTH Aachen University (gaiac e. V.)