Integration of Plant and Groundwater Interactions - Introduction to Phytoremediation of Contaminated Groundwater - page 29

tree. The branches held the stars and sky upward from the
earth. The upper level was the realm of the gods, called the
Asgard. The middle world was occupied by the Midgard,
and the lower Hel. The World Tree was supported by three
roots, and each root obtained water from three separate wells
supplied by springs. Because these wells would have
contained groundwater, perhaps it is coincidence that the
ash tree is a phreatophyte. A similar legend circulates
among the Buddhists in India, in which a spring runs at the
base of a tree they worship; the tree, being a willow, also is a
phreatophyte. Such images of a World Tree whose roots
extend to groundwater also were used by the Aztecs of
Mexico, who called their phreatophyte Tota. Even the cot-
tonwood tree commonly used in sun dances by Native
Americans is a phreatophyte.

Rain water that falls in the winter goes up in summer, to come
again in winter. And when the winds push these vapors the
waters fall on all parts of the land, and when it pleases God
that these clouds (which are nothing more than a mass of water)
should dissolve, these vapors are turned to rain that falls on the
ground.

His conceptual model, although clear to us today, was not
widely accepted by his contemporaries. This may have been
a consequence of his being accused of heresy for insisting
that fossils were the remains of once living creatures. He
also has been considered the Father of Agricultural Chemis-
try on account of his work with manure application in
cultivated fields to support plant growth over time. A short
biography of this and other hydrological contributions can
be found in Deming (2005).

2.1.2 Renaissance and Observation

2.1.3 Experimentation and Testing: The
Beginning of the Scientific Revolution

Previous speculation during the Middle Ages about natural
processes that followed theological proclamation began to
be replaced by rational thinking and observational
approaches that characterize the Renaissance Period in the
fifteenth and sixteenth centuries (Durant 1953). Perhaps the
best example of understanding the movement of water
through direct observations rather than speculation is that
provided by Leonardo da Vinci (1452-1519). He spent
countless hours near streams and waterfalls, meticulously
drawing the paths taken by seeds he threw into the water.
Da Vinci, however, continued the notion of the Greeks that
water rose from the oceans to the mountains through under-
ground reservoirs, similar to observations he made of blood
rising in the body to supply flow to a cut. Da Vinci had a
fundamental understanding of the hydrologic cycle, how-
ever, and wrote in his notebooks (Curdy 1923)

The beginning of a more modern approach to understanding
the movement of water in the hydrologic cycle was the
quantification of observations that occurred in the seven-
teenth century. During this period, science emerged as a
systematic method of inquiry about observations of the
natural world with less influence from theological ideology
(Durant 1953).
In the late 1600s, Pierre Perrault (1608-1680) wanted to
determine if enough precipitation occurred to supply the
flow observed in rivers that drained a basin. Until this time
it was thought that precipitation amounts were insufficient to
supply the flow in rivers, and that these flows were
supplemented with water from underground caverns that,
in turn, were supplied by ocean water that entered through
holes in the ocean floor. This made sense, as previously
discussed, because rivers typically flow even when no pre-
cipitation has recently fallen. Between 1668 and 1670,
Perrault measured the precipitation that fell in the basin
that drained to the Seine River. Then he made what may
have been the first measurement of the discharge of water
out of a basin. When Perrault multiplied the amount of
precipitation by the drainage basin area, he found that the
amount of precipitation, P , was six times greater than the
discharge, Q , of water from the valley (Fig. 2.1 ), as stated in
1674 in De l'origine des fountains ( Treatise on the Origin of
Springs ).
A more accurate measurement of the flow of water in the
Seine River was perfected later in 1686 by Edme Mariotte
(1620-1684). To measure flow, he measured the velocity of
the river by using floats to calculate the distance that the
float, being a surrogate for a particle of water, traveled per
unit time and multiplied this velocity by the measured cross-
sectional area, or the water depth multiplied by the river

Or do you not believe that the Nile has discharged more water
into the sea than is at present contained in all of the watery
element? Surely this is the case. If then this water had fallen
away from the body of the earth, the whole mechanism would
long since have been without water. So therefore one must
conclude that the water passes from the river to the sea, and
from the sea to the rivers, ever making the same-self round, and
that all of the sea and the rivers have passed through the mouth
of the Nile an infinite number of times.

Because this process still invoked the transfer of water
from oceans to mountains, Gregory Reisch (1467-1525)
attributed such upward water movement to suction. Indeed,
suction can move water against gravity, but not the great
distances required to support these hypotheses.
Insightful explanations about the movement of water that
did not include the need for underground transfer of ocean
water to the mountains were made by the potter and geolo-
gist Bernard Palissy (1510-1590) in Discourse Admirables
in 1580, such as