The Keota news., 1913-06-20
Too Steep Grades Are Sometimes
Responsible for Leaks.
When bitches Arc Built Through
oraveliy Soils seepaoe Losses
Arc Naturally Heavy UnIess
Measures Are Taken TO
Prevent.

There Is not an irrigating canal in
this country from which there is not
more or less loss of water In transit.
These losses are generally spoken Of
as caused by seepage and evaporation.
However it has been demonstrated
that the evaporation losses as COM
pared to those caused by seepage are
SO light that they may be disregarded.
The loss by seepage unusually occurs
from the character of the soil through
which the canals run. says the Denver
Field and Farm. When this Ii finely
divided sandy loan such as occurs In
many places the losses from this
cause are generally light. but when
the canals are built through soils
which are very gravelly or perhaps
nearly pure gravel the seepage losses
uous measures are adopted to prevent
them.
In other places much water Is lost
along parts OF the canals where the
excavation has been through seamy
basaltic rock or decomposed sand
stone. Too steep grades sometimes
are responsible for much seepage.
This condition is found on some OF
the smaller early bitches built through
gravelly soil. We have heard 1t argued
that when the water is to be conduct
ed through gravel or porous forma-
ton 1t should go fast, but In canals
built on this theory the velocities are
such as to prevent sitting Of the chan
nels and thus actually promote seep-
age. In the construction of canals
many fills are made across short gul-
lies or depressions, where to follow
the contour of the land would necessi-
tate wide detours; and frequently the
upper banks are either omitted or de-
stroyed which allows the water to
spread out over the land above the
canal and form lakes.
In cases where the fills are Of con-
siderable height quite large areas of
land are sometimes flooded and below
such lakes are invariably found heavy
seepage losses. large enough often to
run in small streams away from the
canal. To prevent these losses the
upper banks of the canals have been
built up so as to prevent the forma-
ton Of the lakes. On the canals
where the difficulty is due to gravelly
soil 1t has been the practice to some
extent to excavate foot or 80 below
grade and then fill in with clay or fine
material, so as to form a puddle. The
clay is tamped in the bottom, and then
the bottom and sides are plastered
several inches thick with a mortar
formed of the clay in plastic state.
This is then covered with layer of
gravel to prevent washing.
The results of this work are quite
satisfactory, but it is difficult to find
suitable clay for the purpose and CO.
ment has to be used which is more ex-
pensive but considerably more dur
able. Some measurements have been
made on our canals to learn the extent
of seepage. but on the smaller ditches
1t is almost impossible to get any 70
liable results on account Of the numer
GUS diversions which there Is no sat
isfactory means of measuring: and II
these are shut of along stretch two
or three miles long, the extra water
will cause such rise in the canal be-
low as to be dangerous. The loss Oft
en- amounts to fifty per cent. and this
is more than any business can stand.