Agriculture Reference
In-Depth Information
4.1 INTRODUCTION
Irrigated agriculture plays a major role in the livelihoods of nations all over the world
and South Africa is no exception. With irrigated agriculture being the largest user of
runoff water in South Africa, there have been increased expectations from govern-
ment that the sector should increase efficiency and reduce consumption in order to
increase the amount of water available for other uses, in particular for human domes-
tic consumption. Irrigation in South Africa is currently practiced on 1.6 × 10
6
ha. In
2000, it used 62% of the runoff water that was used by all sectors, or 39.5% of the
exploitable runoff water [6]. Studies and research over 40 years, on flood-, mobile-
and micro irrigation techniques contributed to the knowledge base of applying irri-
gation methods 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 flows under gravity over soil
while infiltrating is applied to the farm lands. This includes basin, border, fur-
row and short furrow.
• Mobile irrigation systems, which move over the farm land under their own
power while irrigating. These include center-pivot, linear and traveling-gun
systems.
• Static systems include all systems that remain stationary while water is ap-
plied. We distinguish between two types: 1) Sprinkler by which water is sup-
plied above ground by means of sprinklers or sprayers. This includes perma-
nent or portable like quick-coupling, drag-line, hop- along, big-gun, side-roll
and boom irrigation systems; 2) Micro-systems, which include microsprayers,
mini- sprinklers and drip-irrigation systems.
Aspects that have been addressed in the research were layout, design, selection,
management and a number of other factors that can improve the effi ciency of the ir-
rigation system. However, great emphasis has been placed lately on how an increase
in effi ciency will lead to reduced water consumption by agricultural users and thereby
'release' some of the annual water yield for use by the domestic sector. Recommended
actions to improve effi ciency include measurement of the quantity of water distributed
and applied at specifi c times; preparation of water-use effi ciency 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 to date by the Water Research Commission
(WRC) demonstrate how improvements can be made to effi ciently manage water in
South Africa.
4.2 IMPROVEDFLOOD-IRRIGATION APPROACH
Increasing the efficiency of flood irrigation has been intensively researched in South
Africa since 1972 by engineers of the Department of Agriculture - Division of Agri-
cultural Engineering and implemented as such. It was only in the late 80s and early 90s
that, through a WRC-supported project, aspects such as the upgrading of the layout, the
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