Groundwater

Natural groundwater resources are stored in aquifers, which are permeable rock formations, or in unconsolidated deposits (sands, silts or gravels). The main characteristics of groundwater systems are:

• invisible and relatively inaccessible locations;

• low flow rates;

• long residence times; and

• slow reactions to changes on the surface.

Groundwater plays a number of important economic and ecological roles, as well as being an essential element of human health. Groundwater systems are normally very stable, in both quantity and quality.

However, the effects of pollution and overexploitation could lead to drastic changes, with the period of recovery lasting centuries.