Successful Irrigation
through
Agricultural Engineering
Article & Photos by Felix B Reinders
AGRICULTURAL RESEARCH COUNCIL,
INSTITUTE FOR AGRICULTURAL ENGINEERING
P
roducing of food and fibre
by irrigated agriculture
plays a major role in the
livelihoods of nations all
over the world and in South Africa
it is not different. With the agricultural water use sector being the
largest of all water use sectors in
South Africa, there have been increased expectations that the sector
should increase efficiency and reduce consumption in order to increase the amount of water available for other uses.
The purpose of an irrigation system
is to apply the desired amount of
water, at the correct application
rate and uniformly to the whole
field, at the right time, with the
least amount of non-beneficial water consumption (losses), and as
economically as possible.
Studies and research by agricultural
engineers in South Africa over 50
years on the techniques of flood-,
mobile- and micro-irrigation contributed to the knowledge base of
designing and applying irrigation
systems correctly. With irrigated
agriculture being the largest user of
runoff water in South Africa, there
has been increased expectations
that the sector should increase efficiency and reduce consumption in
order to increase the amount of
water available for other uses, and
in particular for human domestic
consumption. Irrigation in South
Africa is currently practised on
1 600 000 hectares and use 62% of
the runoff water. Studies and research
contributed
to
the
knowledge base of applying irrigation systems correctly to improve
the efficient application of water.
The different irrigation systems vary
in terms of individual components,
cost and performance and generally
they can be classified into three
groups:
Flood
irrigation systems by
which water that flow under
gravity over soil while infiltrating
is applied to the farm lands. This
includes basin, border, furrow
and short furrow.
Mobile irrigation systems which
move over the farm land under
its own power while it irrigates.
These include centre pivot, linear
and travelling gun systems.
Static systems include all systems
that remain stationary while water is applied. We distinguish
between two types:
Sprinkler by which water is
supplied above ground by
means of sprinklers or spray-
ers. This includes permanent
or
portable
like
quickcoupling,
drag-line,
hopalong, big gun, side-roll and
boom irrigation systems.
Micro which includes microsprayers, mini-sprinklers and
drip irrigation systems.
Aspects that were addressed by the
agricultural engineers in the research were layout, design, selection, management and a number of
other factors that can improve the
efficiency of the irrigation system.
However great emphasis has been
placed lately on how an increase in
efficiency will lead to reduced consumption by agricultural users and
thereby “release” some of the annual water yield for use by the domestic sector. Recommended actions to
improve efficiency include measurement of the quantity of water distributed and applied at specific
times; preparation of water use efficiency and risk management plans;
and a reduction of the quantity of
water used for irrigation by existing
farmers through investment in appropriate technology.
Various research projects funded by
the Water Research Commission
(WRC), the Agricultural Research
Council’s-Institute for Agricultural