The Leavenworth echo. [volume] (Leavenworth, Wash.) 1904-current, 1921-05-13
WHAT HAPPENS TO GROUND
WATER AND WHY
BY :. L. Winters in Scientific
American

american.
A thief in the night. the water
supply Of irrigation canals is absorb
ed and robbed by the soil which J.,
necessarily given quarters in the con
Veying channels and impounding res
CRY oirs Of the arid region Of the West.
Capillary action is the force in oper-
alton which is credited with appro-
Iratlng water not accounted for hv
direct percolation and evaporation.
The irrigation engineer has hereto
fore found scant information on the
subject; hence the value Of a series Of
experiments recently conducted by
the Drainage Division, United State
Bureau Of Public Roads, under the di-
rection of the senior engineer of it.
Berkeley. Cal, laboratory.
What Is the significance of capil-
lal1ty as an agency in stealing water
from irrigation works does il play a
conspicuous part in distributing.
within the soil, moisture applied in
irrigation, and whether / conspires
with plant growth along the canal
bank in consuming water designed
for producing crop wealth on arid
lands-these and similar questions
prompted the scientific study whic
required special apparatus. Duration
and frequency in the distribution or
Earnessed water constitute an uncer-
tain equation Of constant concern t.
the irrigator Uniform distribution
a water and the maintenance there
Of cannot be ignored if dry lands are
to he transformed into crop-producing
areas. Likewise economy in the an
plication of water Is a factor wher
even the offerings of the clouds are
not TO be had for the asking. Oh
vlously, the capillary movement Of
soil moisture is not foreign to the
proper construction and operation Of
conveying channels and impounding
eseTvOirs-avenues for the econom-
zeal application Of water to the fields
The tests were pronounced in their
conclusions that the movement or
moisture by capillary action is much
slower and not so extensive in the alb
sence Of free water as in the presence
Of the latter Gravity plays a con
spicuous role in the capillary move
ment Of moisture when wet and dry
soils come in contact. The force OF
oapillary attraction is greater in q
horizontal direction than the upward
tendency in vertical boxes, but not SC
great as tic downward movement. i
the variation in movement of mos
ture in the several test boxes, as rep
resenting the upward. downward and
horizontal position is primarily at
tributable to gravity, the conclusion
Of the government irrigation enginee1
is that Newton's law is the outstand-
lnc influence in thc capillary distribu-
ton Of soil moisture
The rate of movement OF moisture
as sketched en- a diagram. shows its
progress in the lighter soils Is more
rapid for the first few hours and then
siackens its pace more quickly than
with the heavy soils The heavie,
soils maintained . more uniform vari-
ation than the lighter soils through
cut the experiment The light Idaho
land, for example. evidenced a varia
tion of nearly $50 per cent in the to-
tai distance moved during a 30-day
test. Not including sandy lands. the
volume Of water necess ary TO move
tho moisture tho first inch was about
tho same or 81 ghtly less than the re
oUirement for conveying the last incl
on a basis of 3G-daY tests The differ
ence in the percentage Of moisture
discovered near the bottom and tina
found near the top of a vertical col
umn Is cause for inference that more
water to tho inch i removed for the
bottom inches than for the top ones.