Environmental Enlightenment #309
Groundwater is vital for our existence. The information below has been extracted from a publication by the United States Geological Survey and enriched with images borrowed or procured on the web.
The ground-water environment is hidden from view. From observations on the land surface, we form an impression of a “solid” Earth. We do not see the myriad openings that exist between the grains of sand and silt, between particles of clay, or even along the fractures in granite.
It is estimated that the total volume of subsurface openings (which are occupied mainly by water, gas, and petroleum) is on the order of 125,000 cubic miles beneath the United States alone. If we visualize these openings as forming a continuous cave beneath the entire surface of the United states, its height would be about 186 feet.
Most subsurface openings contain water, and the importance of this water to mankind can be readily demonstrated by comparing its volume with the volumes of water in other parts of the Earth’s surface.
Limiting our discussion to freshwater only, we find:
84.96% in ice sheets and glaciers
14.1% in ground water
0.55% in lakes and reservoirs
0.3% in soil moisture
0.05% in atmospheric vapors, and
0.04% in rivers.
Many people are surprised to learn that only 14% of all fresh water is groundwater.
If we eliminate ice sheets and glaciers, 94% of all surface and subsurface freshwater is groundwater.
Enjoy the spring.
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