Historical Foundation of Plant and Groundwater Interactions - Introduction to Phytoremediation of Contaminated Groundwater - page 15

Fig. 1.6 An aerial view of the
San Andreas Fault in Coachella
Valley, California, seen here as a
faint line running vertically in the
middle of the picture.
Groundwater flows from left to
right in the alluvial sediments
deep underground to discharge to
the surface along the fault, thus
supporting dense forests of
phreatophytes, the dark masses
along the left side of the fault in
the picture, in an otherwise arid
area (Modified from Proctor
1968). These clusters of growth
related to geologic structure are
called vegetative scarps.

native date palms, they also were areas of the initial
concentrations of many people, including today. In fact,
the control of subsurface water, such as the Mountain Aqui-
fer that receives recharge by precipitation that falls on the
West Bank, is a continuing source of tension (Nativ 2004).

1.2.3 First Observation of Plant
and Groundwater Interaction

O.E. Meinzer and another USGS scientist, Walter N. White,
in the mid-1920s decided to observe more fully the interac-
tion between plants and groundwater. To accomplish this
goal, they investigated a crop of alfalfa ( Medicago sativa )on
a farm in the arid Escalante Valley of Utah that was planted
in 1922 and irrigated for only 1 year. Meinzer and White
installed observation wells during 1926 and 1927 to deter-
mine the depth to the water table, which varied between 6
and 15 ft (1.8 and 4.5 m) below land surface. On July 13,
1927, they excavated the complete root system of an alfalfa
plant near an observation well. Upon excavation, they made
a meticulous drawing of the relation of the root system to the
measured depth to groundwater. The soil to a depth of 8.5 ft
(2.6 m) was clay and peat loam, below which was mostly
sand and gravel. With the highest water table at 6.5 ft
(1.9 m), the roots grew in the direction of higher moisture
content as the depth to water table increased to below 10 ft
(3 m) (Fig. 1.8 ). During the period of high water table, the

Fig. 1.7 An oasis, similar to that depicted above, is generally
characterized by tall palm trees, a welcome sight unique to desert
areas often devoid of other vegetation. Oases are present because
geologic features such as faults in underlying rocks and overlying
sediments create a zone of less permeable material (the dashed line ),
which causes horizontally flowing groundwater ( arrows ) to flow
upward toward land surface. Plants such as shallow-rooted palms or
deep-rooted cottonwoods, tap this groundwater and thrive even though
little current precipitation exists.

supplies water to oases that characterize the area. These
oases were instrumental in sustaining nomadic tribes (Issar
1990). Because the oases provided water and food from