Assessing the effect of construction-induced consolidation on groundwater travel time distribution under unconfined conditions

Estimation of groundwater travel time distribution (TTD) is critical to environmental assessment and successful urban water management. This paper presents a novel analytical approach to account for the groundwater TTD in an unconfined aquifer, considering the impervious urban structure and the modified aquifer hydraulic properties due to consolidation processes. The analytical solution follows the Dupuit-Forchheimer assumption and is verified through comparisons with numerical results. Sensitivity study reveals a potential increase in the mean travel time when the aquifer intersects with an impervious underground structure, while the degree of change depends on the interplay of two mechanisms (i.e., the increase in upgradient groundwater storage and the decrease in pore space of the consolidated zone). Global sensitivity analysis suggests that urban groundwater TTD systems are strongly dependent on both construction-related parameters and aquifer compressibility, indicating that adaptive strategies of groundwater management should be taken for different aquifer types. The proposed analytical model has great implications for the management of water resources in urban areas, the utilization of urban groundwater for human consumption, and the quality of urban aquifers.