Agriculture Reference
In-Depth Information
For calculation of DU of low one-half, substitute “low quarter” by “average low-
half depth received or infiltrated.”
The DU lq has been applied to all types of irrigation systems. In trickle irriga-
tion, it is also known as “Emission Uniformity.” In sprinkler situation, it is termed
“Pattern Efficiency.”
The relationship between DU and UCC can be approximated by (USDA, 1997 )
UCC
=
100-0.63 (100-DU)
DU
=
100-1.59 (100-UCC)
Distribution uniformity is primarily influenced by the system design criteria.
Poor uniformity of application is often easily identified by differences in crop
response and/or evidence of surface waterlogging or dryness. The part of the field
receiving more than the average depth may suffer from inefficiencies due to water-
logging and/or runoff, while the other part receiving less than the average may suffer
from undue water stress. Thus, uniform irrigation is important to ensure maximum
production and minimum cost.
4.2 Performance Evaluation
4.2.1 Concept, Objective, and Purpose of Performance Evaluation
4.2.1.1 Concept
Performance terms measure how close an irrigation event is to an ideal one. An
ideal or a reference irrigation is one that can apply the right amount of water over
the entire area of interest without loss.
Evaluation is a process of establishing a worth of something. The “worth” means
the value, merit, or excellence of the thing.
Performance evaluation is the systematic analysis of an irrigation system and/or
management based on measurements taken under field conditions and practices
normally used and comparing the same with an ideal one.
Traditionally, irrigation audits are conducted to evaluate the performance of exist-
ing irrigation systems. A full irrigation audit involves an assessment of the water
source characteristics, pumping, distribution system, storage, and in-field applica-
tion systems. However, audits are also conducted on several components of on-farm
irrigation system.
4.2.1.2 Objectives
The modernization of an irrigated area must start with a diagnosis of its current
situation. Following this procedure, the specific problem affecting water use can
be addressed and that may lead to a feasible solution. The specific objectives of
performance evaluation are as follows:
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