Agriculture Reference
In-Depth Information
can be made. This may be at water management area (WMA) scheme or farm
level where different sources of information are available for assessment.
3. Scenario development phase: During this phase, alternative scenarios were
developed for the components requiring change, and the feasibility of imple-
menting the changes was assessed from technical, environmental and eco-
nomic perspectives. Models were used for feasibility assessment, making use
of available computer programs and datasets.
4. Implementation phase: In this phase recommendations were made for imple-
menting feasible changes, and guidelines were developed.
These guidelines should be promoted among all levels of stakeholders (WMA,
scheme and farm), as a means of infl uencing the way in which water-use effi ciency is
reported at the different management levels, for example, in water-use effi ciency ac-
counting reports, water-management plans and water-conservation plans.
Within this phase, the main outcome was developed, viz. 'Standards and Guide-
lines for Improved Effi ciency of Irrigation Water Use from Dam Wall Release to Root
Zone Application' [11]. The structure and con- tent of the Guidelines are based on
the lessons learnt locally and internationally during the course of the project. Hence,
the conventional set of performance indicators with benchmarks was moved away
from and a water-balance approach is instead being promoted as a more meaningful
and sustain- able approach to improving water-use effi ciency in irrigation.
These Guidelines are aimed at assisting both water users and authorities to achieve
a better understanding of how irrigation water management can be improved, thereby
building human capacity and allowing targeted investments to be made with fewer
social and environmental costs. The guidelines comprise of four modules:
• Module 1: Fundamental concepts.
• Module 2: In-field irrigation systems.
• Module 3: On-farm conveyance systems.
• Module 4: Irrigation schemes.
The guidelines developed as part of this project contain information on aspects of
irrigation water-use effi ciency that is either new or supplements previously available
information:
• The ICID framework was applied to reassess the system efficiency indicators
typically used by irrigation designers when making provision for losses in a
system and converting net to gross irrigation requirement. A new set of system
efficiency (SE) values for design purposes has been developed. These values
are illustrated in Table 3 and are considerably more stringent than previous
system-design norms.
• System efficiency defines the ratio between net and gross irrigation require-
ments (NIR and GIR). NIR is therefore the amount of water that should be
available to the crop as a result of the planned irrigation system and GIR is
the amount of water supplied to the irrigation system that will be subject to the
envisaged in-field losses.
• The new application efficiency values are shown in the 'Norms' column of
Table 3, while the different water-use components and their losses at the point
 
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