BGR Bundesanstalt für Geowissenschaften und Rohstoffe

Groundwater

Groundwater resources of the worldGroundwater resources of the world Source: BGR & UNESCO

Groundwater flows in the upper earth's crust representing thus the subsurface and invisible part of the water cycle. It is generated mainly by infiltration of precipitation into the underground, but a smaller fraction is produced by seapage from surface water. Contrary to surface water, groundwater does not flow along channels or dipping or, as often wrongly alleged, along "water veins" but rather appears everywere in the saturated zone below the water table. There it flows generally at low velocity through porous media or through fractures and karstified zones in hard-rock milieus following the gradient towards discharge streams or rivers.

Depending on the hydraulic conductivity of the media, an aquifer or an aquitard can be defined. Aquitards are mainly composed of fine and low conductive material like silt and clay. Aquifers can be differentiated threefold: porous, fractured, and karstified. Porous aquifers are composed of sand or pebbles and constitute the most yielding aquifers. Fractured aquifers are hard-rock media in which groundwater flows along fractures and fissures. They generally show lower storage availability than porous media. If due to leaching processes in the underground the fractures become channels or cavities, the aquifers are known as karstified. This kind of aquifer is typical for carbonate rocks like lime and dolomite. Karst aquifers are very sensitive to pollution because of the general absence of protective soil, the large flow velocities, and the short residence time of groundwater in the aquifer.

The DIN 4049 defines groundwater as underground water that fills the openings of the earth’s crust. Its movement is exclusively or almost exclusively determined by the gravity and the frictional forces originated during the movement.

Groundwater represents not only a natural resource, but also an economical commodity. As such, it fulfils important economic functions: it is the most used natural resource and an important source for drinking water supply. Thus, for industry and agriculture this natural resource represents an essential production factor.


Contact 1:

    
Prof. Dr. Thomas Himmelsbach
Phone: +49-(0)511-643-3794
Fax: +49-(0)511-643-2304

Contact 2:

    
Dr. Jörg Reichling
Phone: +49-(0)511-643-2366, Mobil: 0151-11717161
Fax: +49-(0)511-643-532366

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