Water management from an irrigator's perspective - Greenmount Press

Water Matters
Water management from an
irrigator’s perspective
By Janelle Montgomery 1 & John Doble 2
Nathaniel Phillis has been irrigating
for 15 years. He is currently the
contract irrigator with Sundown
Pastoral Company (SPC) and manages
a team that is dedicated to improving the
management of water on ‘Keytah,’ Moree.
This dedication is encouraged through
a bonus system that the contract team has
negotiated with the employer. Nathaniel
recently spoke at the Gwydir Valley Irrigators
Association ‘Innovations in Irrigation’
field day discussing water management,
irrigation performance and water use efficiency
from his perspective.
As the contract irrigator, Nathaniel drives
improvements in water use efficiency on
Keytah. He manages the water from the
time it arrives on farm either from the river
system or rainfall. Nathaniel’s team moves
the water around farm and applies it to the
fields with the aim to reduce losses and
therefore improve the water use efficiency
of all components of the irrigation system –
storages, distribution (channels) and fields.
In the beginning there were some management
issues that needed to be resolved
between the Irrigation Contractor and
Farm Management. How could Nathaniel
improve whole farm efficiency without influence
on major issues like maintenance of
gates, rottobuck placement, monitoring onfarm
water volumes and repair and maintenance
program to supply channels, head
ditches and tail water return systems
In order to maximise water management,
Nathaniel’s team needed to be able
to address these issues themselves. He
negotiated a works budget which allowed
these areas to fall within his responsibility.
For example there are over 400 gates on
Keytah, and each of these have now been
recorded, numbered and prioritised for
any repairs and maintenance.
…12s
It is important to match siphon size and number to ensure a consistent flow rate along
the length of the field.
Nathaniel Phillis drives improvements in water use efficiency on Keytah.
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10 — THE AUSTRALIAN COTTONGROWER FEBRUARY–MARCH 2009

Water Matters
Nathaniel Phillis is responsible for irrigating 120 hectares of lucerne and 120 hectares of cotton this season using a lateral move system.
w10…IRRIGATOR’S PERSPECTIVE
Field design
An important first step to improving water
use efficiency was to understand the hydrology
of Keytah’s field design. This meant
measuring the head height differences along
the head ditch and matching siphon size
and number to ensure a consistent flow rate
along the length of the field.
Figure 1 shows the difference in head
height and flow rates if all sets were watered
with two 2.5 inch (6.3 cm) siphons
on one Keytah field. The flow rate ranges
between 6.0 and 9.7 litres per second.
This variation in flow rate has a significant
effect on the advance with water
reaching the end of the tail drain at various
times. If siphons were pulled at the one
time the distribution uniformity would vary
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between furrows, with parts of the field
underwatered, while other parts would be
overwatered.
Ensuring a consistent flow rate has improved
uniformity and assisted with labour
management. Tail water flows are more
consistent, so irrigators are not waiting for
rows to come through and they can irrigate
more hectares per day.
Maintenance
Field and headditch maintenance is crucial
for improving irrigation performance.
Lasers are used on graders during the
maintenance program to ensure the delivery
systems and structures are as close
to design as possible. Tail drains and drop
box heights are also managed to reduce
the amount of silt.
With plenty of tractor driving experience,
Nathaniel says the hardest tractor
driving operation on the farm is building
rottobucks, and believes the person starting
the siphons should build the rottobucks
as they are the individual on the shovel
if there are any breakouts during the irrigation.
This ensures greater care in their
placement.
Evaporation trial
It is well understood that evaporation
from on-farm storage can be the largest
loss of water on farm. Nathaniel is currently
conducting an on-farm trial in conjunction
with the National Centre for Engineering
in Agriculture (NCEA) to investigate the
benefits of applying Aquatain to on-farm
storages to reduce evaporation losses. All
storages have now been surveyed to obtain
an accurate depth-volume calibration
curve so storage volumes are known and
they are monitored on a regular basis.
These changes in water management
do put greater demands on the irrigators,
both physically and mentally, and a good
team is vital for improved irrigation performance.
It is a challenging exercise to
increase awareness of management that
improves water use efficiency and encourage
practice change. But this has been
achieved by actually calculating and benchmarking
their WUE, striving for further improvements
and putting a dollar value on
these improvements.
1
NSW DPI and Cotton Catchment Communities
CRC, Moree; and,
2
Gwydir Valley Irrigators Association.
Figure 1: Difference in head height and flow rate across a field
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12 — THE AUSTRALIAN COTTONGROWER FEBRUARY–MARCH 2009