The Ordway new era., 1911-07-07
PLAN OF IRRIGATION
Waterfall Should Be Uniform
Throughout the Ditch.
Increased Productiveness Of Meadows
Within Last Twenty-Five years
Duo In Great Measure to
Fertllizlno Sediment.

In constructing ditch the fall.
whether great or small. should be uni.
form throughout Any diminution OF
the fall will cause sediment to settle
and I'LL the ditch at that point. The
greater the fall Of the ditch. espe-
cially at the headgate. the greater will
be the amount Of sediment drawn
IRON the stream. 1t is customary to
construct q dam in q stream at the
headgate at right angle to the current
TO secure the full capacity at low
water. A shear dam apexed to the
headsate, II the fall is light, will
throw more Of the finer silt into the
ditch. While II the fall 10 great II
will cause too much coarse sand to
enter. writes E. A. Mitchell In the
Denver Field and Farm.
Distinctions. such as rock dams or
boards. driven In the bottom Of ditch
10 raise the water level SO as to
spread over meadow are wrong In
principle. as they always cause sedi-
ment to settle above the distractions.
The rock. sods or boards should be
placed at the side OF the ditch to mar
row but not obstruct the middle or
bottom OF the channel. The irrigatinS
knolls or high places. the laterals
should not end at the highest point.
but extended through and beyond.
thus allowing sand and the heavier
particles OF sediment to be carried
past and discharged on the slope,
Small vents should be cut to conduct
water over the high places. II the
ditch ends ut the highest point. the
current ceases there and sediment Is
deposited where not needed. making
the knoll higher and more difficult Of
irrigation.
When there Is an abundance OF
sediment In q stream 1t can be made
to play an important part In leveling
rough places on the fields II properly
applied. The vents cut in the main
bitches or laterals to spread the
water when the land is rough and un-
even should diverge 1t at an acute
angle from the ditch. instead Of the
customary way of at right angles.
This will carry the sediment with the
current into the vents, thence out on
to the meadows to finally settle in the
depressions. whereas II the vents are
cut at right angles. the force OF the
current naturally deposits most OF the
sediment against the obstructing low
er side Of the vent and soon fills
itself. In fact to draw on all sedi.
nent possible every vent should be
cut on the oblique.
Any pioneer will have noticed the
increased productiveness OF native
meadows within the last twenty-five
years. This in a great measure can
be accounted for from the fertilizing
effect of deposited sediment. In 1889
! cut over a barren coarse sand and
gravel bar OF a few acres In extent
In Gunnison county that then looked
to be worthless for hay land. This
same bar Ia now covered with black
soil built up in the Intervening years
and produces heavy crop OF wire
grass. All erosive material carried
down from the mountain sides con-
tains a more or less percentage OF
raw phosphates, the very essence Of
concentrated fertilizer. A crude home
made analysis Of hardened cake OF
sediment one and one-half inches
thick deposited in a depression on a
meadow last year gave the following
results under the glass:
Silt consisting Of decomposed AMI
NAL and vegetable humus. seven
eighths of an inch: finely eroded par
ticles OF volcanic rock. one-eighth
inch; sand and mica, one-half inch.
This cake was cut In circular form,
agitated in a gold pan with water.
then turned into a circular pan Of the
same diameter Of the cake Of sedi-
ment and allowed to settle and the
water to evaporate. A percentage Of
sand Is necessary to maintain the
porosity of the soil for best growth
Of plant life. In former times irriga-
ton high up near the sources of
mountain streams was either not
needed or practical. Copious rains in
silt countries where irrigation of the
lower valleys was necessary. supplied
sufficient moisture for the higher val
leys, therefore the value of the sedi-
mentation near the source of streams
was never studied. We yet too little
understand its value in the semi-arid
valleys of the great Rocky mountain
region. Plowed an, cultivated fields
allow irrigating wal> to leach out
or wash away their best elements.
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