Agriculture Reference
In-Depth Information
In order to apply this framework to irrigation areas, typical components of the
water-infrastructure system are defi ned wherein different scenarios may occur. In
South Africa, most irrigation areas make use of a dam or weir in a river from which
water is released for the users to abstract, either directly from the river or in some
cases via a canal (Figs. 2-4). Water users can also abstract water directly from a
shared source, such as a river or dam/reservoir, or the scheme-level water source
could be a groundwater aquifer. Once the water enters the farm, it can either contrib-
ute to storage change (in farm dams), enter an on-farm water distribution system or
be directly applied to the crop with a specifi c type of irrigation system. The South
African framework covers four levels of water-management infrastructure as shown
below (Table 1):
1. The water source;
2. The bulk conveyance system;
3. The irrigation scheme and the irrigation far; and
4. The relevant water-management infrastructure.
TABLE 1
Four levels of water management infrastructure [11].
Water management level
Infrastructure system component
Water Source
Dam/Reservoir
Aquifer
Bulk conveyance system
River
Canal
Irrigation scheme
On-scheme dam
On-scheme canal
On-scheme pipe
Irrigation farm
On-farm dam
On-farm pipe/ canal
In-field irrigation system
The different components of the water-balance framework system and their clas-
sifi cation according to the ICID framework, for whichever agricultural water-man-
agement system, have been developed as a guide to identify the different areas were
water losses can occur. In order to improve water-use effi ciency in the irrigation sec-
tor, actions should be taken to reduce the nonbenefi cial consumption (NBC) and non-
recoverable fraction (NRF). Desired ranges for the NBC and NRF components have
been developed to assist the practitioner in evaluating the results obtained when fi rst
constructing a water balance.
Finally, it is recommended that the water user's lawful allocation is assessed at the
farm edge, in order to encourage on-farm effi ciency. At scheme level, conveyance,
distribution and surface storage losses need to be monitored by the water user asso-
ciation (WUA) or other responsible organization.
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