It is now widely accepted that groundwater, though not as visible as surface water, is ubiquitous in the global landmass, is contained in the pore spaces of rock formations (aquifers), and its science, hydrogeology, has rapidly developed over the last 35 years. This science has contributed to...

Transboundary aquifers are present in all parts of the world, ranging from hundreds to tens of thousands km 2 . The largest have fresh water to provide the planets drinking water needs for 200 years, e.g. the Guarani. Intensive use of most of the larger transboundary aquifers has not yet taken...