Geography of the World’s Groundwater: A Hierarchical Approach to Scale-Dependent Zoning

The description and analysis of local, regional or global groundwater conditions are of practical use only if the groundwater information is properly linked to well-defined geographic locations or zones. Most hydrogeological maps do so by presenting values or patterns of hydrogeological variables superimposed on a simplified topographic map. For various purposes, however, it is helpful to relate the groundwater information to predefined spatial units or zones with hydrogeologically meaningful boundaries. Such zones can be defined at different scale levels, according to the geographic dimensions of the case considered and the spatial resolution required. In this chapter, a hierarchical approach to scale-dependent groundwater zoning is presented. It includes three levels: (1) ‘aquifers’ or ‘aquifer systems’ at the local level; (2) ‘groundwater provinces’ at the intermediate level; and (3) ‘global groundwater regions’ at the macro-level. Each of the delineated 36 global groundwater regions is subdivided into a number of the 217 proposed groundwater provinces. Each of the latter, in turn, includes one, several or many of the aquifer systems present on Earth. The proposed zoning system has potential to contribute to organising, deepening and disseminating knowledge on the World’s groundwater.