Preprints
https://doi.org/10.5194/hess-2022-330
https://doi.org/10.5194/hess-2022-330
 
04 Oct 2022
04 Oct 2022
Status: this preprint is currently under review for the journal HESS.

Impact of urban geology on shallow groundwater

Ane LaBianca1,2, Mette Hilleke Mortensen1, Peter Sandersen1, Torben O. Sonnenborg1, Karsten Høgh Jensen2, and Jacob Kidmose1 Ane LaBianca et al.
  • 1Geological Survey of Denmark and Greenland (GEUS), Copenhagen, Denmark
  • 2Department of Geosciences and Natural Resource Management, University of Copenhagen, Copenhagen, Denmark

Abstract. This study examines the impact of urban geology and spatial resolution on the simulation of shallow groundwater levels and flows at the city scale. The study uses an integrated hydrological model based on the MIKE SHE code that couples surface water and 3D groundwater simulations with a leaky sewer system. The effect of geological configuration was analyzed by applying three geological models to an otherwise identical hydrological model. The effect of spatial resolution was examined by using two different horizontal grid sizes in the hydrological model, respectively 50 m and 10 m. The impact of the geological configuration and spatial resolution was analyzed based on model calibration, simulations of high-water levels, and particle tracking. The results show that a representation of the subsurface infrastructure, and near terrain soil types, in the geological model impacts the simulation of the high-water levels when the hydrogeological model is simulated in 10 m resolution. This was detectable even though the difference between the geological models only occurs in 7 % of the volume of the geological models. When the hydrological model was run in 50 m horizontal resolution, the impact of the urban geology on the high-water levels was smeared out. Results from particle tracking show that representing the subsurface infrastructure in the hydrological model changed the particles’ flow path and travel time to sinks, both in the 50 m and 10 m horizontal resolution of the hydrological model. It caused less recharge to deeper aquifers and increased the percentage of particles flowing to saturated zone drains and leaky sewer pipes. In conclusion, the results indicate that even though the subsurface infrastructure and fill material only occupy a small fraction of the shallow geology, it affects the simulation of local water levels and substantially alters the flow paths. The comparison of the spatial resolution demonstrates that to simulate this effect the spatial resolution needs to be of a scale that represents the local variability of the shallow urban geology.

Ane LaBianca et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on hess-2022-330', Anonymous Referee #1, 03 Nov 2022
  • RC2: 'Comment on hess-2022-330', Anonymous Referee #2, 14 Nov 2022
  • RC3: 'Comment on hess-2022-330', Anonymous Referee #3, 29 Nov 2022

Ane LaBianca et al.

Ane LaBianca et al.

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Short summary
This study explored the effect of Anthropocene geology and computational grid size on the simulation of shallow urban groundwater. Many cities are facing challenges with high groundwater levels close to the surface, yet urban planning and development seldom consider its impact on the groundwater resource. The study illustrates that the urban subsurface infrastructure significantly affects the groundwater flow path and residence time of shallow urban groundwater.