Environmental Engineering Reference
In-Depth Information
Table 1.1
Relation of the depth to groundwater and occurrence and height of mesquite trees in the Salton Sea area of California, United States
(Modified from Brown 1923).
Well location
Depth to ground water
from land surface,
in ft (m)
Character of mesquite growth
Nature of soil
Palen Mountains,
Adams well
20(6.1)
One lone mesquite bush beside well, others not far away
Stream gravel
Eagle Mountains,
Anshutz well
8(2.4)
Small clumps of mesquite in vicinity; trench cut in side of canyon
shows roots of mesquite penetrating crevices of rock to water
Granite, somewhat
jointed and sheared
Blair well
34(10.3)
Abundant mesquite, 10 to 12 ft high
Very porous sand,
forms dunes
Chuckwalla well
7.5(2.2)
Mesquite abundant locally in bed of dry arroyo
Stream gravel and
clay
Cook well
75(22.8)
None
Porous sand
Imperial
80(24.3)
None
Porous sand and silt
Indian wells, post
office
34(10.3)
Abundant forests of mesquite 10 to 15 ft high
Porous sand, forms
dunes
Stemberg well
45(13.7)
Scattering growth 2 to 3 ft high
Sandy silt
Palo Verde Valley
12(3.6)
Heavy timber over large areas
Porous sandy silt
Table 1.2
Relation of depth to groundwater and the occurrence of different herbaceous and woody phreatophytes; X indicates the plant was
present (Modified from Meinzer 1927).
Depth to water
table (feet)
Seepweed
(
Dondia
)
Mexican salt grass
(
Eragrostis obtusiflora
)
Alkali sacaton (
Sporo-
bolus airoides
)
Chamiso
(
Airiplex spp.)
Mesquite (
Prosopis
glandulosa)
4
X
4
X
X
10
X
X
20
X
X
30
X
1.2.7 G.E.P. Smith, Plants, and Groundwater
Fluctuations
surface (Fig.
1.10
). The alkali zone was dominated by salt
grasses, such as those described in the experimental studies
of Lee (1912), which are adapted to high concentrations of
salts left in the upper layers of soils after the evaporation of
shallow water. The mesquite zone was located on the sides
of slopes composed of sediment deposited by streams, called
tallus, that drained the adjacent San Andreas Mountains.
Here, depths to groundwater approach 50-80 ft
(15.2-24.3 m) because of the porous nature of the coarse
materials. Finally, the greatest depth to groundwater, in
excess of 100 ft (30.4 m), was characterized only by the
creosote bush.
Cross-sectional diagrams made by Brown (1923) also
were used to relate the influence of depth to groundwater
on the types of plants observed in a particular basin, and he
included a description of the vigor of the plants. For exam-
ple, Brown drew cross-sectional diagrams in areas where
mesquite growth appeared to be stunted as the depth to
groundwater increased, which appeared to be more of a
controlling factor than a result of differences in soil chemis-
try. He confirmed this observation by measuring the depths
to groundwater in wells. His results are summarized in
Fig.
1.11
.
Approaches to investigate the interaction between plants and
groundwater systems that were undertaken by researchers in
the early 1900s seem simple by today's standards. At that
time, however, the hypothesis that plants interact with
groundwater was novel. Use of simple methods during the
1920s provided direct evidence of the interaction between
plants and groundwater in the arid southwestern United
States. However, it remained unclear if this interaction
could be measured more accurately than relating certain
plants to the depth to groundwater.
The work of G.E.P. Smith in the mid-1910s started to
provide a foundation for addressing this question that still is
relevant today in the context of using phytoremediation to
achieve hydrologic control of contaminant plumes in
groundwater. Smith was an irrigation engineer with the
University of Arizona, and he recognized the inherent diffi-
culty in using soil-filled tanks to measure transpiration, as
was made evident from Lee's investigations (Lee 1912).
Smith used a more direct method that involved placing
automatic water-level recorders in wells installed in a forest
Search WWH ::
Custom Search