Hydrogeology
The hydrologic cycle shows that when rain falls to the ground, some water flows along the land surface to streams or lakes, some water evaporates into the atmosphere, some is taken up by plants, and some seeps into the ground. As water begins to seep into the ground, it enters a zone that contains both water and air, referred to as the unsaturated or vadose zone. The upper part of this zone, known as the root zone or soil zone, supports plant growth and is crisscrossed by living roots, holes left by decayed roots, and animal and worm burrows. Below lies an intermediate zone, followed by a saturated capillary fringe, which results from the attraction between water and rocks. As a result of this attraction, water clings as a film on the surface of rock particles. Water moves through the unsaturated zone into the saturated zone, where all the interconnected openings between rock particles are filled with water. It is within this saturated zone that the term "groundwater" is correctly applied. Groundwater is held in formations called “aquifers”.
Myth: Groundwater occurs as an underground river or lake, or in “veins”.
Fact: Only in caves or within lava flows does groundwater occur this way. Instead, groundwater is usually held in porous soil or rock materials, much the same way water is held in a sponge.
Groundwater resources within the arid to semi-arid Namibia form an integral part of the water supply to the country. To illustrate the importance of these resources to the country, it should be pointed out that basically only the central northern- (the 4 O-regions) and central regions of Namibia (around Windhoek ), as well as the towns of Rehoboth, Mariental and Keetmanshoop make use of surface water. The remainder of Namibia mainly relies on groundwater as the only supply of potable water – even along the perennial rivers there is a significant dependency on groundwater.
Without the knowledge gained through hydrogeology, we have no way of predicting what will happen to our groundwater resources or the future effects of groundwater abstraction on the environment.
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