Hydrological research in TERENO-Northeast
To explain and predict variations of water levels in lakes of north-eastern Germany, it is essential to understand the interactions between hydrosphere, atmosphere, geosphere and biosphere in these groundwater-lake-dominated hydrological systems. Possible reasons for widely observed declining lake water levels are climate change, land use change, or human impact by water management measures such as drainage of wetlands.
Several research questions are of particular interest in this respect: a) how strong is the connectivity between lakes and the groundwater system? b) how variable in time and space is groundwater inflow to the lakes? c) are lake responses dominated by the large-scale groundwater system or small-scale heterogeneities? d) what is he role of geology and morphology in the landscape that is dominated by (peri-)glacial deposits? e) what are the dynamics, trends and controls of groundwater recharge? f) do quick flow processes in the unsaturated zone play an important role? g) how do land use and climate change affect water inflow to lakes, its flow paths and dynamics, and its water quality?
An important prerequisite for describing and understanding flow processes in the unsaturated zone is monitoring soil moisture dynamics. Soil moisture time series at the point scale and estimates of soil moisture data from remote sensing must be linked via cutting edge sensors technologies operating at the intermediate scale (i.e., sensor networks, GNSS reflectometry, Cosmic Ray Neutron Sensors and Gravimetry). We explore these techniques based on the broad existing expertise at GFZ in the fields of GNSS, remote sensing and gravity. Novel monitoring data, in particular, are gravity time series as observed by high-precision superconducting gravimeters directly in the field. Contrary to other soil moisture observations, changes in gravity are an expression of total water storage variations in the subsurface, including all depths of the unsaturated zone and the aquifers.