Xander Huggins , Tom Gleeson, Karen G. Villholth, Juan Carlos Rocha , James S. Famiglietti

Groundwater is a dynamic component of the global water cycle that performs important social, economic, ecological, and Earth system functions. Identifying the patterns and relationships between groundwater’s diverse functions can provide important insights to aid framework, model, and theory development on interactions between groundwater and its connected systems and can help generate context-appropriate management approaches to the global groundwater crisis. We harness the recent growth in global groundwater datasets and perform an archetyping analysis using sequenced self-organising maps to derive a novel typology of groundwater systems based on its diverse, large-scale system functions that include storage capacity, climate coupling, groundwater-dependent ecosystems, irrigation, and water management. Our results, a 5-arcminute (~10 km) global map of 10 clearly discernible groundwater system archetypes (GAs), present a data-driven, integrated typology of groundwater’s large-scale socioeconomic, ecological, and Earth system functions. Each archetype represents a distinct configuration of functions that reoccur over broad spatial extents. We evaluate archetype distributions across the 37 large aquifer systems of the world. Some aquifers are dominated by only a few archetypes (e.g., the Amazon and Congo Basins) whereas others contain a complex mosaic of many archetypes (e.g., Song-Liao and Maranao Basins). Yet, every large aquifer system we analysed is characterised by multiple archetypes, highlighting the insufficiency of treating these groundwater systems as homogeneous units in global groundwater assessments, models, and management. This archetyping study offers a further step towards developing causal understandings of system behaviour in these dynamically intertwined, complex, large-scale systems connected to groundwater.