Evaluation of performance of semi-portable sprinkler irrigation systems in Markazi Province

Approximately 94% of the total renewable sources of water is allocated to agricultural. Total irrigation efficiency in this section is estimated to of less than 43%. By using of new Irrigation methods, water consume efficiency can be increased. Correct selection of irrigation system is an important section in optimal operation of water resources. The necessity to pay attention to the characteristics and limitations of irrigation systems, the physical and chemical properties of water and soil, the environmental, economical and social Consequences, cause the selection of irrigation system become a relatively complex problem. One of the pressurized irrigation methods is semi-portable sprinkler irrigation systems. These systems have not been evaluated in some areas of Markazi province. Also, in some areas such as Arak plain that had been previously evaluated, due to the long time span and also increasing of area under cultivation, re-examination is needed. So, the performance of 10 semi-portable sprinkler irrigation systems was investigated in Arak, Shazand, Khondab and Kamijan areas.

This research includes collecting basal information, field measurements and software calculations. To determine the wind speed and direction during the test, anemometer was used. To determine the soil moisture, chemical and physical properties, samples was taken and sent to laboratory before experiment. All field testing were carried out during irrigation and also windless or low wind speed days. In each test, hydraulic variables of system, such as pressure of sprinklers, were measured at the time of performance. a pressure gauge was installed on next raiser and pressure was measured instantaneously to Increase Accuracy. The flow rate of the sprinklers was also measured by volumetric method using two hoses, a 20 Liter gallon and a chronometer. For more Accuracy, the flow rate of each sprinkler was determined from the catalog data of each sprinkler. It has been attempted to select the location of the sprinklers in points where pressure is moderate. The water collecting cans, all 15 cm in height and 15 cm in width, were placed in a 3 * 3 meter mesh. Then after an hour of operation, system was shut down and the water inside cans was measured using a calibrated measuring cylinder and was written in a form. After field operations and collecting of required data, computational operations were performed to determine the technical evaluation parameters of the system. The evaluation parameters in this study include Coefficient of Uniformity (CU), Distribution Uniformity (DU), Application Efficiency of Low Quarter (AELQ) and Potential Efficiency of Low Quarter (PELQ), that calculated for both testing block and Total system.

The results of evaluation in 10 systems indicate that due to inappropriate design and implementation, all of the evaluation parameters are less than allowed range (81% ≥ 81% CU and 81% ≥ 67%), but also Mismanagement is effective. In all of these systems, due to lack of precipitation and depletion of groundwater surface, farmers use deficit- irrigation, which Equality of application and Potential efficiency prove this. On the other hand, exception of KF system, in all systems, the number of simultaneous sprinklers in operation is increasing compared to those in the approved design, which is one of mismanagement that leads to decrease of pressure and Spray radius can't be estimated that caused in lack of distribution uniformity and resulting in inadequate irrigation in some areas and deep penetration losses in other areas. Increasing the number of simultaneous water sprayer in operation is a significant Objection. The actual efficiency of 37.9% in KHH2 to 63.8% in the KHN system was calculated. Changes in pressure varied from 13% in the KHH2 to 43% in the KM system. The average discharge varied from 1.7 L/s in KHF to 2.88 L/s in KF system and spray losses were estimated from 5.5% in the KHN to 32% in the KHF system. Distribution uniformity in the test block varied from 47% in the KF to 71% in KHN and Coefficient of Uniformity varied from 58% in KHH1 to 83% in AG system. Distribution Uniformity in all system varied from 44/3% in KF to 68/5% in SHJ system. The Potential Efficiency of Low Quarter of the test block varied from 39.5% in KHH2 to 67.3% in the KHN system and in whole system varied from 37.9% in the KHH2 to 63.8% in KHN system. The Application Efficiency of Low Quarter of the test block varied from 39.5% in KHH2 to 67.3% in KHN system and in whole system varied from 37.9% to 63.8%. In conclusion, according to the results of this study, semi-portable sprinkler irrigation systems in plains of the Markazi province are not in good condition and have various design and implementation problems.