Impacts of hydrogeological heterogeneity on groundwater transit time

Groundwater transit time refers to the travel time of a water molecule through an aquifer from recharge at the water table to discharge at a surface water body (e.g., river). Analysing transit times provides a primary way to understand the overall transport characteristics of a hydrological system and is of interest in many aspects of environmental management. For example, studying transit time distribution can facilitate the mitigation of pollutant transport risks and ecosystem restoration. Hydrogeological heterogeneity of an aquifer is a major controlling factor for groundwater flow paths and transit time distributions. In this study, we investigate the impacts of spatial variability of hydrogeological properties on transit times by combining measurements and a new semi-analytical numerical modelling scheme. Passive tracer transport data from several catchments in Europe are obtained from open databases. Groundwater transit time in these catchments are inferred from both tracer transport data and numerical modelling. Comparing the results in different catchments provides a comprehensive way of understanding the impact of hydrogeological heterogeneity on groundwater transit time.