ABSTRACTION OF WATER FROM LOWER GROUND LEVELS
It is not widely known that a plentiful good quality potable water supply can be procured from water bearing strata deep in the earth all over the world, but how has this water found its destination?
Origin and Occurrence of Ground Water
The Earth’s water cycle is the continuous circulation of moisture and water on our planet. The cycle has neither a beginning nor an end, but the concept of the water cycle commonly begins with the waters of the oceans, since they cover about three-fourths of the earth’s surface.
Radiation from the sun evaporates water from the oceans into the atmosphere. The water vapour rises, and then collects to form clouds. Under certain conditions, the cloud moisture condenses and falls back to the earth as rain, hail, sleet or snow – the various forms of precipitation. Hydrologists and others call this “water of meteoric origin”.
Precipitation that falls upon land areas is the source of essentially all our fresh water supply. We depend upon it to replenish the quantity that is taken from lakes, streams and wells for man’s numerous uses.
Some of this precipitation, after wetting the foliage and ground, runs off over the surface to streams. Another part soaks into the soil. Much of the water that enters the soil is detained in the plant root zone and eventually is drawn back to the surface by plants or by soil capillarity (the interaction between contacting surfaces of a liquid and a solid that distorts the liquid surface from a level plane). Some of it, however, soaks below the plant root zone and under the influence of gravity continues moving downward until it enters the ground water reservoir.
Upon joining the body of ground water, the percolating water moves through the pores of saturated subsurface materials and may reappear at the surface in areas at lower elevations than the level where it entered the ground water reservoir. Ground water discharges naturally at such places in the form of springs and seeps which maintain the flow of streams in dry periods. The streams, carrying both surface run-off and natural ground water discharge, eventually lead back to the oceans.
The water cycle then, is the system by which nature circulates water from the oceans through the atmosphere and returns it both overland and underground back to the sea through devious paths – some short and some long, in terms of both time and space.
The forces involved in this process include radiation, gravity, molecular attraction and capillarity.