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Groundwater Development For Portable Water Supply
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CHAPTER ONE
HISTORICAL BACK GROUND AND GROUND WATER THEORIES
Groundwater
development dates from ancient times the Old Testament contains numerous
references to groundwater, springs, and wells, other that dug wells,
groundwater in ancient times we supplied from horizontal wells known as
QAUNATS. These persist to the present day and can be found in a band
across the regions of the South Western Asia and North Africa extending
from Aghanistan to Morocco. A cross section a long a qanat ie shown in
fig 1.1 typically, a gently sloping tunnel dug through alluvial material
leads water by gravity flow beneath the water table at its upper end to
a ground.
A vertical cross section along a qanat surface
outlet and irrigation canal at its lower end. Vertical shafts dug at
closely s paced intervals provide access to the tunnel. Qanats are
laboriously hand constructed by skilld workers employing techniques that
date back 3000 years.
Iran possesses the greatest concentration of
qanats; here some 22,000 qanats supply 75 percent of all water used in
the country. Lengths of qanats extend up to 30km, but most are less than
5km. The depth of the qanat mother well (see fig 1.1) ie normally less
than 50m, but instances of depth exceeding 250m have been reported.
Discharge of Qantas varies. Seasonally with water table fluctuations and
seldom exceed 100m3/hr.
GROUNDWATER THEORIES
Utilization of
groundwater greatly preceded understanding of its origin, occurrence,
and movement. The writing of Greek philosophers to explain origins of
springs and groundwater contain theories ranging from fantasy to nearly
correct accounts. As late as the seventeenth century it was generally
assumed that water emerging from springs could not be derived from
rainfall, for it was believed that the quantity was in adequate and the
earth too impervious to permit penetration of rain water for below the
surface. Thus, early Greek philosophers such as Homer, Thates and Plato
hypothesized that springs were formed by seawater. Conducted through
subterranean channels below the mountains, then Aristotle suggested that
air enters cold dark caverns under the mountains where it condenses
into water and contributes to springs.
The Roman philosophers,
including Seneca Pliny, followed the Greek ideas and contributed little
to the subject. An important step forward, however was made by the Roman
architect Vitnvius he explained the now accepted infiltration theory
that the mountains receive large amounts of rain that percolate through
the rock strata and emerge at their base to form streams.
The Greek
theories persisted through the Middle Ages with no advances until the
end of the Renaissance. The French Poffer and Philosopher Bernard
Palissy (1510 – 1589) reiterated the infiltration theory in 1580, but
his teachings were generally ignored. The German astronomer Johannes
Kepler (1571 – 1630) was a man of strong imagination, who likened the
earth to a huge animal that takes in water of the ocean, digests and
assimilates it, and discharges the end products of these physiological
processes as groundwater and springs. The seawater theory of the Greeks,
supplemented by ideas of vapourizaton and condensation processes within
the earth, was restated by the French Philosopher Rene’ Descarfes (1596
– 1650).
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ABSRACT - [ Total Page(s): 1 ]Groundwater hydrology may be defined as the science of the occurrence distribution, and movement of water below the surface of the earth. Geochydrology has an identical connotation, and hydrogeology differs only by its greater emphasis on geology. Utilization of groundwater dates from ancient times, although an understanding of the occurrence and movement of subsurface water as part of the hydrologic cycle has come only relatively recently.SCOPE: Groundwater referred to without specification is ... Continue reading---
