The Sidney herald., 1957-02-28
By Frank Wodnik,
Agricultural Engineer Sos


Agricultural Engineer Sos
Drains r constructed on irri-
gated land to protect or reclaim
costly and potentially highly pro-
ductive agricultural areas. AS ir-
igated areas r being developed
drainage problems are becoming
more acute. Practically every ir-
rigation project which has been
in operation for a few years is
affected to some degree by high
water table or accumulation of
alkali salts. The irrigation pro-
jects in the Yellowstone Valley
are no exception, many drainage
problems related to high water
table and alkali exist in this area.
Drains constructed on irrigated
land may be divided into two
types, surface drains and sub-sur-
face drains. Surface drains are
usually quite shallow and are
constructed primarily for drain
ing surface water from the low
areas of fields. Sub-surface drains
r usually many feet deep and
r designed to intercept the un-
foreground water. The immediate
effect of no surface drainage is
a reduction of crop yields by
drowning out low areas. The long
range effect of no surface drain
age is the teaching out of crop
nutrients and if seeping water
cannot escape from underground
drainage, the continual impound-
ing of water on the fields con-
tributes to a rising water table.
To lower this high water table
1t probably will be necessary to
construct drains that will inter-
cept underground water.
Land may be defined as having
a high water table when the
ground hears the surface, to a
point, where there is surplus
amount of water in the root zone.
Problems related to water table
are many and varied. The con-
tinued use of irrigation water US
ually is accompanied by a ris-
ing water table, because in most
irrigated areas, the application
OF irrigation water is relatively
inefficient. Irrigation efficiency
run in various areas, have
that the efficiency with
which farmers apply irrigation
to crops, ranges from Is to
10 per cent. That is, from Is to
10 per cent of the water turned
IN the fields will be available to
he plants, the remainder will be
oSt to run-off, deep percolation
md evaporation. AS the water ia
Die rises carer the surface, crop
gradually decrease. Some
irrigation farmers believe that
leeping the water table within a
iew feet of the surface, produces
high yields. But, in areas where
llkali salts r present, as here in
he Yellowstone valley, the tenn
,orary favorable condition of the
water tables is followed by
serious decrease in yields, if not
.omplete loss of production due
alkali concentration. High
water tables are not entirely caus-
d by inefficient water applica-
ion and inadequate surface
lrainage. Another factor contrib
ting to a high water table is
Inlined canals and supply later
Is. Irrigation canals contracted
through pervious materials such
S sand and gravel furnish con-
iderable quantities of water to
he underground supply.
AS the water table rises, so do
he alkali salts. If all irrigated
and were underlain with a per-
ious sug soil and good under
round drainage, it would then
e possible to maintain a move
lent of water continuously down
rard. If this were the case, there
rould be little trouble from aka
on irrigated farms. A Con-
downward movement of
lrge quantities of water would
radually leach out large quan-
ties of soluable salts, in
lie zone, where plants get
lost of their food. But in areas
here the water table is high, the :
onward movement of water
, limited. The flow of ground
alter is obstructed usually by an ]
lpervious soil bearer of dixie
Id since the water cannot flow {
underground channels it
ses upward. AS a result, the ir- I
or surface water moves {
,wn until it reaches the under
'ound water. AT this point leach
G and downward movement of
lrface water stops and in periods
irrigations the ground I
alter moves upward bringing clo- I
r to the surface the salts, which \
e present in the lower depths of (
e soil profile. These salts some +
mes rise completely to the sur
&c forming white areas or COM ;
only called alkali spots. 6
Many miles of drains have been q
instructed in the past through
w areas and below terrace 7
Iges to protect and reclaim irri- =
ted land here in the Lower (
allowstone Valley. But, there is
i'll q Oroot naoI for aI1i+iopol q