COPING WITH THE SILENT REVOLUTION OF INTENSIVE GROUNDWATER USE M.R. Llamas Spanish Royal Academy of Sciences P. Martínez-Santos Dept. Geodynamics, Universidad Complutense of Madrid Abstract Over the last decades, agriculture in arid and semi-arid countries has experienced a true “silent revolution” of intensive groundwater use. Millions of independent farmers worldwide have chosen to become increasingly dependent on the reliability of groundwater resources, and as a result their countries have reaped abundant social and economic benefits. The magnitude of these benefits is such that groundwater probably constitutes the only viable alternative to meet the goals of the United Nations Millennium Declaration. Data from several countries shows that groundwater irrigation presents a greater efficiency, up to ten times higher, than that of surface water irrigation systems, thus contributing to fulfil the motto of “more crops and jobs per drop”. If this situation is confirmed globally, the usual world water visions have to be significantly reviewed. However, the silent revolution has been carried out with scarce control on the part of government water agencies, and thus a series of unwanted effects have developed in certain places. While these by no means justify the pervasive “hydromyths” and obsolete paradigms that voice the frailty of groundwater, appropriate management of groundwater resources remains a worldwide challenge. This paper provides an overview of these issues, and concludes with the necessity there is to educate all levels of society on the importance of groundwater and to create bottom-up user associations to manage aquifers as common pool resources.