Historical Foundation of Plant and Groundwater Interactions - Introduction to Phytoremediation of Contaminated Groundwater - page 17

1.2.5 John S. Brown and the Salton Sea

transpiration over time. Although this experimental design
was an excellent idea, the experiment turned out to be
inconclusive, because the roots of the salt grass died before
reaching the artificial water table. However, Lee's novel
experimental approach did demonstrate an early recognition
of plant interaction with groundwater and the potential effect
of this interaction on the water budget. More importantly,
Lee's research stood in stark contrast to other contemporary
research being conducted in the western United States
by others, including scientists in the USGS, who did not
incorporate the potential use of groundwater by plants into
their overall water budgets. As such, Lee's study heralded
the beginning of similar investigations in the 1920s, such as
those previously discussed by Meinzer and White. (Perhaps
O.E. Meinzer and C.H. Lee should be considered the fathers
of plant and groundwater interactions.)
Other desert plants were shown to interact with ground-
water. Mesquite trees ( Prosopis spp. ) had long been known
to have an extensive and deeply penetrating root system,
even during the time of Meinzer's studies. Pictures of roots
exposed along river banks in the early 1900s clearly depict
the great depths reached by mesquite roots often exceeding
50 ft (15.2 m) (Fig. 1.9 ).

Other early investigations of the relation between ground-
water and woody plants can be traced to work by John S.
Brown of the USGS, as he studied the water resources of the
Salton Sea region of California (Brown 1923). Brown's
research included recording the depths to water table in
areas where the occurrence and height of mesquite trees
were measured, and the soil types recorded. As can be seen
from a subset of Brown's data presented in Table 1.1 , as the
depth to groundwater approaches land surface, both the
presence and growth of mesquite trees increases; when
the opposite occurs, the abundance and growth of mesquite
trees decreases. Brown's observations also reveal that there
may be a limit to the depth that even mesquite roots can
reach and support growth, because no mesquite trees were
observed in areas where depths to groundwater, as measured
in wells, exceeded 75 ft (22.8 m), particularly in well-
drained porous sands. This maximum depth of mesquite
growth supports observations described earlier that noted
mesquite roots did not exceed 50-60 ft (15.2-18.2 m), as
had been recorded in areas exposed along stream banks.

1.2.6 Phreatophyte Facies

As the study of the interaction between plants and ground-
water became more numerous, O.E. Meinzer summarized
the apparent relation between type of plant, both herbaceous
and woody, that dominated in a particular area and the depth
to water table, as measured in nearby wells. Part of his
summary is depicted in Table 1.2 .
The relation between the presence and growth of mes-
quite trees and depth to groundwater also was the subject of
mapping activity that depicted the depths to water-table
elevations in multiple wells, called contour maps, with
respect to the dominant types of plant growth. As Meinzer
and R.F. Hare of the USGS studied the Tularosa Basin in
New Mexico, they produced maps of the types of vegetation
that essentially grew in various clusters, or facies, and the
relation of these phreatophyte facies to the depth to ground-
water measured in wells (Meinzer and Hare 1915). Meinzer
and Hare (1915) claimed the dominant controlling factor on
plant distribution in arid areas was the occurrence of and
depth to groundwater.
Meinzer and Hare (1915) also defined various phreato-
phyte facies as having different plants, but dominated by a
particular species. These zones included the barren zone, the
alkali zone, the mesquite zone, and the creosote bush zone.
Other zones were described, but the zones listed above are
characteristic of the most dominant ones. The barren zone,
as would be expected, was devoid of vegetation, even though
depth to groundwater was less than 25 ft (7.6 m) below land

Fig. 1.9 The more than 50-ft (15.2 m) deep root system of a mesquite
( Prosopis spp .) tree exposed along the eroded bank of a river (Modified
from Gatewood et al. 1950).