Two-thirds of the Earth is covered by water yet less than one per cent of the world’s freshwater is accessible for use. Groundwater is the largest component (about 70%) of the accessible freshwater. The amount of water stored in groundwater systems or aquifers is greater than that of all rivers, lakes and the largest man-made reservoirs combined. More than half of the global freshwater supply for drinking, industrial uses and irrigation comes from groundwater. However, what the general public and most decision-makers know and understand about groundwater is usually very little. Today, knowledge of groundwater around the world, its functions and its use is increasing rapidly, and views about the many ways in which groundwater systems are linked with other systems are changing accordingly.

In terms of making a contribution to securing water availability and groundwater-related environmental values, managing groundwater resources sustainably is of vital importance to society and the environment.

Although most of the world’s groundwater at conventional well drilling depths is of good quality, it remains a major concern to protect this water against quality degradation and to prevent poor quality groundwater from entering active freshwater cycles. Anthropogenic groundwater pollution and its control have been major issues for many decades. It is a complex field because of the many sources of pollution, the myriad substances that may be involved, large variations in the vulnerability of aquifers, the lack of monitoring data and uncertainties on what impacts excessive concentrations of pollutants have. Because groundwater usually moves very slowly, groundwater pollution is almost irreversible, or at least, very persistent.

Hydrogeologists and other scientists have made remarkable progress over the last few decades in collecting information on the world’s groundwater systems, in understanding their role and functions, in observing changes over time and in identifying options for enhancing benefits from groundwater as well as threats that need to be addressed to safeguard the resource’s sustainability. Gradually it has become clear how strongly the development and state of groundwater systems are interrelated with other systems and external drivers. It has also become clear that the value of groundwater is not limited to its abstraction for multiple uses (provisioning services), but includes a range of valuable in situ services (regulatory services), such as supporting wetlands, springs, baseflows and the stability of the land surface. As a result, the management of groundwater resources has evolved into a multidisciplinary activity that addresses multiple objectives.

>> Access to a selection of UN publications on groundwater