Imperial Valley press., 1938-02-14
DISTRICT
REPORT
CONTINUED


Editors Note: Herewith is a
4 continuation of the engineers
survey recently submitted to I'm
j pcrial Irrigation District Bond
81 holders on the physical and eco
3 nomic condition of the district.
4 Imperial Valley readers should
S realize that the report embOdies
81 the opinions of firm of hired
8 consultants who, being human,
q are subject to error. We do not
i agree with all conclusions voiced
: in the report, but we believe ii
= comprehensive enough to justify
1 its publication as a means of Civ
ID ing our readers comprehensive
: view of the district and its prob
lens.
Today the productivity of large
areas is materially less than it was
= i'm the past. This situation has been
corrected locally by drainage; addi-
tional drainage is necessary.
NECESSITY FOR
DRAINAGE
Much of the deposits forming the
valley fill were laid down under
water, and are consequently so
finely divided as to be almost i'm
pervious. Other portions of the allu-
vial deposits were laid down during
| floods when the river overfloWed
to the north and while somewhat
coarser are still resistant to the
free movement of water. In fact,
so deficient is the entire valley
fill of gravel deposits, that domes
tic wells have been generally i'm
practicable and resort has always
been made to water from the irri
| CATION bitches for service to indi-
VidualS and to communities.
This geological condition makes
il entirely impracticable to resort
To drainage by pumping from the
underground supply, as was done
SO successfully in the Salt River
Valley i'm Arizona. When develop
ment of new lands takes place on
the mesaS east and west of Impe-
rial Valley, it may be that these
areas can be drained by pumping
out the excess grOundwater. If this
can be done, this method of drain
age will take care of these new
lands and minimize the hazard
to existing areas which would re-
suit from the irrigation of higher
lands bordering them.
Open drainage bitches of the
| type used in the Rio Grande val
ley, and in many places in the
central valleys of California, are
only effective to a limited degree
in the Imperial Valley. In regions
where open drainage bitches have
been used to good advantage, there
exists a continuous body of ground
water which moves with reasonable
freedom through the pervious sub
soil The Sub-sOil in the Imperial
Valley, on the other hand, is gen
orally resistant to the movement
| Of groundWater under much of the
| valley Actually we are advised that
dry ground is found at compare
lively short distance below many
| irrigated fields.
rial Valley are partially successful,
the surplus irrigation water moves
slowly toward these through thin
strata of soil which is more perV-
ious than the general mass of the
alluVium Since there is a practi-
cal limit to the depth of drains,
their influence is rarely felt more
than a few hundred yards away.
For example, there are instances
along New river channel and along
the Alamo where the water will
stand in test holes within a few
feet of the surface, in spite Of the
fact that these channes are 30 to
40 feet or n ore in depth.
For many years the district has
kept records of the elevation of
groundWater in a large number
of test wells throughout the valley
Unfortunately, most of these are
located close to canals or laterals
and accordingly may not reflect
field conditions accurately but are
presumably indicative Of relative
conditions in different parts of the
valley When the elevation of
grounwater in these wells IS noted
on a map, a reasonable pattern
Of groundWater contours can be
drawn which would indicate con-
tinuous body Of groundwater were
it not for other conditions which
make this improbable. 1t is more
likely that the appearance Of a
groundWater table results from the
fact that the surface contours in
the valley are generally regular in
form, and the variations in depth
70 water are not large.
Analysis of the data as TO depth
of water at the various test wells
shows clearly that conditions are
worse along the east High Line can
al, and i'm the area west of the
town of WestmorIand. Throughout
a strip severai miles IN width along
the east High Line canal the depth
to grOundwater in the test wells
Is generally within six feet 0r the