Procedures for estimating gross irrigation water requirement from crop water requirement.
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Date
2001
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Abstract
The goal of irrigation is to supply sufficient water for crop growth to all areas within a field.
Therefore, the uniformity of application of irrigation water is of great importance. The
objectives of this study were to quantify the performance of irrigation systems under field
conditions using standard evaluation techniques and to investigate the use of spatial statistics
to characterise the spatial variability of application. The main objective was to develop
techniques to estimate gross irrigation water requirement that incorporates the uniformity of
application.
Different practitioners have given different definitions to the criteria used to evaluate the
performance of an irrigation system. A literature review was conducted to determine the
current definitions used and the factors that affect these performance criteria. The theory and
application of spatial statistics was investigated in order to charaterise spatial distribution
of irrigation water. The spatial distribution of irrigation water under centre pivots was
determined using field measurements. A number of centre pivot, sprinkler, floppy, drip and
micro-irrigation systems were evaluated using standard techniques.
The results from the evaluation of spatial data show that this approach is useful to determine a
map of the distribution of applied irrigation water. Due to the smoothing characteristic of the
spatial statistical method employed, the maps have a uniformity that is greater than in reality.
The results from the standard evaluation techniques show that quick and representative results
for the performance of an irrigation system can be obtained. The distribution uniformity has
an affect on the efficiency of a system and should therefore be included in the calculation of
the gross irrigation water requirement. The methods for these calculations are discussed.
Further research needs to be conducted to determine actual distribution uniformities and
application efficiencies for irrigation systems under various field conditions. This will provide
useful standards to include in the calculation of gross irrigation water requirements.
Description
Thesis (M.Sc.)-University of Natal, Durban, 2001.
Keywords
Irrigation efficiency., Irrigation farming., Theses--Bioresources engineering and environmental hydrology.