So far, our analysis of 'hydropolitics' has been based largely on the visible : rivers, transboundary basins, and surface-level water transfer schemes . But beneath the surface, groundwater reserves embody a hugely important - yet very often overlooked - dimension, particularly across Africa. Today I will attempt to illuminate the need to consider groundwater alongside above-ground, 'blue water' sources and the merits of integrating it with existing water management paradigms by again examining our focus region of southern Africa. Invisible importance As posited in a 2006 USAID report , whilst integrated water resources management spells out a promising framework using surface river basins as the unit of management, it overlooks two key notions: groundwater aquifer systems often don't correspond with the surface water management unit, and groundwater systems are transboundary by nature. This is especially relevant in Africa, where 71 discrete transboundary aquifer...