The Parker post., 1911-07-15
PLAN OF IRRIGATION
Waterfall Should Be Uniform
Throughout the Ditch.
Increased Productiveness OF Meaoows
Within Last Twenty-Five years
Due in Great Measure to
FertiIizing Sediment.

whether great or small, Snoulu 00 o"A
form throughout. Any diminutlon OF
the fall will cause sediment TO settle
and fill the ditch at that point. Inc
greater the fall of the ditch, espe-
cially at the headgate, the greater VIII
be the amount of sediment oraWn
from the stream 1t is customary 10
construct a dam in a stream at the
headgate at right angle to the current
to Secure the full capacity at low
water A shear dam apexeo u lne
headgate, if the fall is ngnt' VIII
throw more of the finer silt INTO the
ditch. While if the fall is great IL
will cause too much coarse sano 10
enter, writes E. A. Mitchell IN the
Denver Field and Farm.
Distractions, such as rock GAINS OF
boards, driven in the bottom or oltcn
to raise the water level 80 as 10
spread over meadow are wrong In
principle, as they always cause seol-
ment to settle above the obstructlons.
The rock, sods or boards should De
placed at the side of the ditch TO mar
row but not obstruct the mldole or
bottom of the channel. The 1rrlgatlng
knolls or high places, the lateraIs
should not end at the highest point,
but extended through and Deyond,
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. the
ditch ends at 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 a stream it 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 If 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 off all sedi-
ment 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
I cut over a barren coarse sand and
gravel bar of few acres in extent
in Gunnison county that then looked
to be worthless for hay land This
same bar is 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 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
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-
tion 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 it's value in the semi-arid
valleys of the great Rocky mountain
region. Plowed and cultivated fields
allow irrigating waters to leach out