Abstract:
The success of sprinkler irrigation system depends on its actual performance at field
condition. So that, evaluation of the actual field performance of sprinkler irrigation is very
important. Therefore, this study was intended to evaluate the irrigation practice and the
infield water application of Arjo Dedessa irrigat ion scheme by measuring the performance
indicators of the irrigation as it is normally practiced. During the study, 12 field experiments
were conducted in the period of December–February 2014/15 at two irrigation command
area, to check uniformity of water application. The soil physical characteristics and the
gravimetric water content were determined in the laboratory. To estimate the crop water
requirement (CWR) and irrigation water requirement (IWR), the cowpat 8 for windows was
used. For the assessment of the systems performance, uniformity coefficient (CU),
distribution uniformity (DU), adequacy of irrigation (AD), application efficiency (Ea), )
evaporation and wind drift losses (EWD) were determined for 3.5, 4.0, 4.5 and 5.0 bar of
hydrant pressure. The result shows the mean application rates for 18m x18m sprinkler
spacing were 4.95mm/hr and the average soil infiltration rates 61mm/hr. The CU obtained
were 74%, 80%, 85%, and 88% at the respective hydrant pressure of 3.5, 4.0, 4.5 and 5.0bar.
Also distribution uniformity (DU values obtained from catch can tests data are 62%, 70%,
76% and 81%at respective hydrant pressure. The values of the system CU and system DU are
very closely to the calculated CU and DU values. The obtained results of the lower quarter
adequacy were 53%, 48%, 52% and 55% for respective operating hydrant pressure of 3.5,
4.0, 4.5 and 5.0bar. The results of potential efficiency of low quarter adequacy (PELQ) value
vary from 41% to 67%. The average of 0.31%, 0.15%, 0.15% and 0.16% of water were lost
by evaporation and wind drift during irrigation at the respective hydrant pressure of 3.5, 4.0,
4.5 and 5.0bar.so that, the estate should use the best combination of the hydrant operating
pressure and set time to be successful and work as planned.
