Recent years in northern Bavaria were characterized by exceptional climatic extremes. Albeit short-term intensive precipitation have become more frequent, large parts of Bavaria did not received the necessary amount of precipitation required for the environment. These periods of drought, in combination with anthropogenic interventions, endanger the vitality of forests, especially in northern Bavaria. In addition, we observe heat waves more frequently and over longer periods, for example during the uncommonly hot summers of 2018 and 2019. The aforementioned events have massively weakened large parts of northern Bavarian forest. Therefore, research is required for exploring new water management strategies to increase the resilience of forest ecosystems.

The research project entails two main objectives. Firstly, an operational framework is provided, which delivers data for seasonal weather forecasting for the region of Franconia. Secondly, the efficiency of decentralized small-scale retention measures in forested areas is investigated.  Micro-topographic terrain modulations, which can achieve very large water retention, can be implemented as:

• Reduced runoff from drainages / ditches.
• The use / construction of swales / very small detention basins
• Adaptation in road construction

These small-scale retention measures could play a critical role in storing precipitation and accumulating soil moisture, thus playing a significant role in enhancing a forest’s resilience to drought.

The Chair of Hydrology and River Basin Management at the Technical University of Munich studies the role of such small-scale decentralized retention measures. Following tasks are set for this purpose:

• A LIDAR based high accuracy terrain survey. By means of modern LIDAR technology, it is possible to create high-resolution terrain images. This is also possible for heavily forested areas, such as our study area. These images are the basis for our subsequent investigations.
• Targeted continuous moisture measurements in the soil at different depths. These take place at two different measurement sites in the study area.
• In addition to the continuous soil-moisture measurements, a dense soil-moisture measurement network will be established. Here, no continuous time series will be recorded, but rather measurements will be taken at regular temporal intervals and various depths of up to 1 m.
• Model-based evaluation of the measures. Using the physically based hydrological model "HydroGeoSphere", relevant components of the water cycle, such as evaporation from soil layers, transpiration of vegetation as well as water fluxes in the unsaturated soil zone are simulated in three-dimensions and evaluated.

The implementation of the project will take place in close cooperation with local stakeholders, such as the forest administration and the “Steigerwald Center”. Findings will be made available to potential decision-makers.

Duration: October 2021 - October 2022
Project Funding: Bayerisches Landesamt für Umwelt (LfU)
Project partners: Center for Climate Resilience and Chair of Regional Climate and Hydrology, University of Augsburg, KIT Campus Alpin, Garmisch-Partenkirchen
Project management at the Chair of Hydrology and River Basin Management (TUM): Prof. Dr.-Ing. Markus Disse, M.Sc. Lucas Alcamo, Dipl.-Geoökol. Michael Tarantik