عنوان مقاله [English]
نویسندگان [English]چکیده [English]
Approximately, 94% of the total water renewable sources is allocated to agricultural. The total irrigation efficiency in this section is estimated to be less than 43%. The water consume efficiency can be increased using new irrigation methods. Correct selection of irrigation system is an important section in optimal operation of water resources. The necessity of paying attention to the characteristics and limits of irrigation systems, the physical and chemical properties of water and soil, and the environmental, economical and social consequences, cause the irrigation system selection to become a relatively complex problem. The semi-portable sprinkler irrigation systems that are categorized as pressurized irrigation systems have not been evaluated in some areas of Markazi province. Although, these systems are previously evaluated in some areas such as Arak Plain, but due to the long time span and increased cultivation area, re-examination is needed.
Therefore, the performance of 10 semi-portable sprinkler irrigation systems was investigated in Arak, Shazand, Khondab and Kamijan areas.
This research includes collecting fundemental information, field measurements and software calculations. An anemometer was used in order to determine the wind speed. The samples were taken and sent to the laboratory before the experiment, in order to determine the both physical and chemical peroperies of the soil such as soil moisture. All testing fields were carried out during the irrigation andwindless or low wind speed days. In each test, system’s hydraulic variables, such as sprinklers pressure, were measured at the time of performance. A pressure gauge was installed on the next raiser and pressure was measured immediately to increase the accuracy. The sprinklers’s flow rate was also measured by volumetric method using a 20-Liter gallon, a chronometer and two hoses. The each sprinkler’s flow rate was determined from its catalog, in order to improve accuracy. We attempted to select the sprinklers’ locations in the points where pressure is moderate. The water collecting cans (each 15 cm height and width) were placed in a 3 * 3 m mesh. Then after an hour of operation, system was shut down and the water inside the cans was measured using a calibrated measuring cylinder. After the field operations and data collection, the computational operations were performed to determine the system’s technical evaluation parameters. 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 are calculated for both testing block and Total system.
The evaluation results of 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 the lack of precipitation and depletion of groundwater’s surface, farmers use deficit- irrigation, which equality of application and potential efficiency prove this. On the other hand, except the 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 mismanagements leading to decrease of pressure. The spray’s radius can not be estimated resulting in lack of distribution uniformity and inadequate irrigation in some areas and deep penetration losses in other areas. Increasing the number of simultaneous water sprayers in operation is a significant objection. The calculated actual efficiency varied from 37.9% in the KHH2 to 63.8% in the KHN system. The calculated pressure changes varied from 13% in the KHH2 to 43% in the KM system. The average discharge varied from 1.7 L/s in the KHF to 2.88 L/s in the KF system and spray losses were estimated from 5.5% in the KHN to 32% in the KHF system. The test block’s DU in the varied from 47% in the KF to 71% in the KHN system and the CU varied from 58% in the KHH1 to 83% in the AG system. The DU in all system varied from 44/3% in the KF to 68/5% in the SHJ system. The test block’s PELQ varied from 39.5% in the KHH2 to 67.3% in the KHN system and in the whole system varied from 37.9% in the KHH2 to 63.8% in the KHN system. The test block’s AELQ varied from 39.5% in the KHH2 to 67.3% in the KHN system and in the whole system varied from 37.9% to 63.8%. In conclusion, according to the results, the semi-portable sprinkler irrigation systems in the plains of Markazi Province are not in proper conditions and have various design and implementation problems.