What is groundwater?

Groundwater may be the most important substance on Earth that most people have never heard of, yet it has quietly influenced the evolution of human culture since its earliest beginnings. The predominant physicalist ontology of modernity has created such a powerful conceptual representation of groundwater, that seemingly incredible benefits have accrued to society globally via our ability to understand and relate to it in this mode. However, this modern ontological lens goes unnoticed and unannounced in most groundwater research. This study aims to broaden existing narratives about what groundwater was, is and could be, by exploring how groundwater has come to be perceived, understood and defined by WEIRD (Western, educated, industrialised, rich, democratic) societies in which the author is embedded. By considering the co-evolution of four fields of human-groundwater development, namely - behaviour, systems, psychology, and culture - this paper explores how originally participatory ways of perceiving and knowing groundwater gave way to increasingly abstracted propositional modes of knowledge. Eventually many humans came to believe that the abstract symbols and modelled quantities which they used to represent reality were actually reality itself. Thus 'modern groundwater' is now commonly defined and related to as a resource, a 'thing' devoid of inherent meaning or value, separate from ourselves, which can be manipulated to our own ends. Greater epistemic reflectivity, and a pivot to working metaphysically with groundwater as a relational process, may lead to more effective responses to some of the global predicaments we currently face. Supplementary Information: The online version contains supplementary material available at https://doi.org/10.1007/s10040-026-03056-9.