Groundwater Travel Time Does Not Automatically Translate into Environmental Harm

Abstract Groundwater travel time is widely used in hydrogeological investigations, contamination assessments, groundwater vulnerability studies, mine closure planning, and environmental impact assessments because it provides a measure of how rapidly groundwater can migrate between sources and receptors. However, travel time alone provides limited insight into environmental significance. Short travel times do not necessarily imply environmental harm, while long travel times do not automatically indicate low risk. Environmental consequences depend on the combined influence of source characteristics, pathway behaviour, groundwater connectivity, attenuation processes, receptor sensitivity, and environmental value. This paper examines the relationship between groundwater travel time, groundwater connectivity, receptor exposure, and environmental consequence. Drawing upon recent advances in groundwater connectivity, environmental risk assessment, receptor-based evaluation, and decision-support modelling, the study demonstrates why travel time should be interpreted as a pathway characteristic rather than an impact metric. Practical examples from contamination assessment, water-supply protection, mine closure, and groundwater-dependent ecosystems are used to illustrate how identical travel times can produce substantially different environmental outcomes. A receptor-centred travel-time framework is proposed that integrates source–pathway–receptor principles, travel-time behaviour, connectivity assessment, receptor sensitivity, and environmental consequence. The framework demonstrates that environmental significance emerges from receptor interaction rather than travel time alone. By moving beyond travel-time metrics and towards consequence-based interpretation, the study provides a more robust basis for groundwater assessment, environmental risk evaluation, groundwater management, and regulatory decision-making.