Tidal Subsurface Analysis (TSA): Using Earth and atmospheric tides to quantify subsurface hydro-geomechanical properties

• Applicant: Professor Dr. Philipp Blum, since 8/2022
• Subject Area: Hydrogeology, Hydrology, Limnology, Urban Water Management, Water Chemistry, Integrated Water Resources Management ; Palaeontology
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 424795466

• Final Report Year: 2023

Final Report Abstract

Groundwater extraction is increasing rapidly in numerous regions across the globe, resulting in severe consequences such as declining water tables, ground surface subsidence, deterioration in water quality, and reduction in stream baseflow, which is vital for numerous ecosystems. The current methods used to understand and predict the impacts of groundwater extraction are unable to rapidly provide the detailed spatial and temporal knowledge of subsurface hydro-geomechanical properties required to better manage the vital resource. To address this issue, Tidal Subsurface Analysis (TSA) is further developed as a new subsurface characterization method. TSA is based on analysing well water level responses to natural forces (e.g., harmonic Earth and atmospheric tides), providing estimations of hydraulic and geomechanical subsurface properties. This offers comprehensive information about subsurface hydraulic and geomechanical properties while significantly reducing associated costs and laborious processes. The primary objective of the project was to gain a fundamental and comprehensive understanding of the potential of TSA. This involved modelling the effects of tides using both analytical and numerical models and assessing the capability of TSA in estimating subsurface properties. To accomplish this, (1) the underlying theory of TSA was thoroughly reviewed while developing a numerical tool that can model the coupled processes, (2) the reliability of the most advanced available analytical solution for realistic subsurface conditions was tested, and (3) a new analytical solution incorporating appropriate boundary conditions to accurately reflect the physics of real-world scenarios was derived. The project conducted three distinct studies, encompassing advanced analytical and numerical modelling, along with a comprehensive analysis of field datasets. This allowed to advance TSA and test its robustness when applied under field settings. In summary, TSA has been proven as an elegant cost-effective approach that can support well establish characterization methods.

Publications

• RHEA v1.0: Enabling fully coupled simulations with hydro-geomechanical heterogeneity. Geoscientific Model Development, 14(10), 6257–6272.
  Bastías Espejo​​​​​​​, José M.; Wilkins, Andy; Rau, Gabriel C. & Blum, Philipp
  
• Groundwater Responses to Earth Tides: Evaluation of Analytical Solutions Using Numerical Simulation. Journal of Geophysical Research: Solid Earth, 127(10).
  Bastias, Espejo Jose M.; Rau, Gabriel C. & Blum, Philipp
  
• Technical note: Novel analytical solution for groundwater response to atmospheric tides. Hydrology and Earth System Sciences, 27(18), 3447-3462.
  Bastias, Espejo Jose M.; Turnadge, Chris; Crosbie, Russell S.; Blum, Philipp & Rau, Gabriel C.