Evening star., 1952-03-05
Desert Growths Steel
Water From Southwest
Mesquite, CROSSWORD Waste
Huge Quontity Annually
By Thomas R. Henry

More than trillion cubic feet Of
water is stolen" annually from the soil
of arid regions Of the Western United
States.
The thieves are "phreatophytes."
plants Of no particular value in them
selves. which depend on ground water
for their supply. They cover about Is
million acres and waste up to Is million
acre-feet of water each year. according
to report to the American Geophysical
Union by T. w. Robinson of the United
States Geological Survey Office at Carson
City, New.
"The water used by these plants" he
says, represents the largest source Of
reclaimable water in the arid Western
States. Although 1t appears feasible to
salvage part Of this water, methods
for doing so have not passed the expert
mental stage. In Nevada. it is estimated,
1t would be practical to salvage sufficient
to irrigate about 133, 900 acres of alfalfa
having crop value of $40 Million"
Native American Plants.
The chief "phreatophyt Mr.. Rob-
inson says. are greaSewood. rabbit brush,
salt grass. willow. cottonwood and mes
quite. These have nothing else in COM
mon. With one exception they are native
American plants. All collect the ground
water through their roots and discharge
it into the atmosphere.
An apparently obvious remedy, 1t is
pointed out, is to destroy this vegetation.
but that is not as easy as it seems. An
attempt was made in Arizona, for ex-
ample, to destroy the salt cedar shrub
by means of flame throwers. This was
successful in killing the trunk and limbs
but not the roots. BY midsummer Of
the following year new growth had
reached height of four or five feet.
Uprooting also was tried. This requires
that all roots be removed. Otherwise
new growth appears from each end Of
a severed root. so that two plants spring
up where one grew before. 4.
Sprays Are Successful.
Success has been attained by spray
ing some areas with plant-killing chem
icals. This is expensive but, the report
points out the return may be heavy.
In Arizona alone, for example, it is esti-
mated that the gross value OF the
Salvageable water would easily exceed
$25 million year.
Once a substituted plant, such as
alfalfa, is established it becomes an
economic user Of the ground water and
returns full value for what it takes.
X X
The most accurate surveying Job in
history has been carried out in connec-
ton with rebuilding activities at the
White House.
Levelings have been carried out and
bench marks set up so that a change Of
as much as four hundredths of an inch
in the elevation of any part of the build
ing can be detected at any time, ac-
cording to the report of Howard s..
Rappleye Of the Coast and Geodetic
Survey to the American Geophysical
Union.
Such minute changes In altitude as
those caused by the expansion in con-
crete due to temperature changes during
the day are shown. The purpose prima-
rily was to detect any changes which
might be taking place during the actual
reconstruction project Because of the
extreme accuracy demanded. several
s changes were made in surveying routine.
Ninety Seven Bench Marks.
4 Altogether. Mr., RappleYe says, 81
bench marks were established around
the building and throughout the White
House grounds. OF these "a were on the
building. These were either brass bolts
Of special design or standard metal
rivets. The ground marks were copper
washers in the roots of trees. bolts on
hydrants, etc.
Among the most interesting develop
ments Of the work, Mr.. Rappleye says
has been the finding Of expansion and
contraction of the walls due to tempera-
ture changes. 1t was necessary to estab-
lish standard elevation of a mark in
concrete at SO degrees Fahrenheit in
order to determine changes from other
causes.