“Looking deep” into shallow ground: scientific drilling and continuous monitoring in recharge areas as a key to the understanding of groundwater quality dynamics and subsurface ecosystem functioning
- 1Friedrich Schiller University Jena, Department of Hydrogeology, Burgweg 11, D-07749 Jena, Germany
- 2Cluster of Excellence Balance of the Microverse, Friedrich Schiller University Jena, Jena, Germany
- 3Leibniz Institute for Applied Geophysics, Department 5 Rock Physics & Borehole Geophysics, Stilleweg 2, D-30655 Hannover, Germany
Core-drilling and groundwater well operation in topographic recharge areas have been rarely applied for groundwater quality monitoring or ecosystem exploration, simply due to lacking of productive water bodies in up to >100 m thick aeration zones. The scarcity of observers and data, and neglection in modelling opposes our efforts to unravel the role of thick hillslope aeration zones for services like water provision, water purification and biogeochemical cycling (Lehmann & Totsche, 2020). To fundamentally understand how groundwater quality comes about as a function of inputs and how climate and land use change will affect this quality, we concentrate our investigations on the soil-aeration zone-phreatic zone continuum in topographic highs. From our Hainich Critical Zone Exploratory in central Germany, we present methods and workflows for low-impact scientific drilling and construction of monitoring wells optimized for representative sampling of the total mobile inventory (Lehmann et al. 2021), and results from the analysis of drill cores, borehole geophysical data and multi-year environmental monitoring data. We found that transient (fluid) flow patterns contribute to groundwater quality dynamics, whereby overall aeration zone-phreatic zone-interactions cause quality fluctuations even in deep and isolated habitats. Results from recent drilling campaigns (2023) comprise the detection of narrow oxic zones (fractures, flow paths) also within mudstone-dominated strata (anoxic aquifer-storeys) and weathering-induced hydrofacies differences that indicate further complexity of habitat structures and ecosystem functioning across recharge(-discharge) zones.
References:
Lehmann, R., Totsche, K. U. (2020). Multi-directional flow dynamics shape groundwater quality in sloping bedrock strata. Journal of Hydrology 580, 124291. https://doi.org/10.1016/j.jhydrol.2019.124291
Lehmann, K., Lehmann, R., Totsche, K. U. (2021) Event-driven dynamics of the total mobile inventory in undisturbed soil account for significant fluxes of particulate organic carbon. Sci. Total Environ. 756, 143774. https://doi.org/10.1016/j.scitotenv.2020.143774
How to cite: Lehmann, R., Aehnelt, M., Grelle, T., Lehne, C., and Totsche, K. U.: “Looking deep” into shallow ground: scientific drilling and continuous monitoring in recharge areas as a key to the understanding of groundwater quality dynamics and subsurface ecosystem functioning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18764, https://doi.org/10.5194/egusphere-egu24-18764, 2024.
