عنوان مقاله [English]
نویسندگان [English]چکیده [English]
Evaluation of irrigating systems is defined as the analysis of the system based on measurement in real field conditions, during the system operation. The evaluation of the system deals with the fact that to what extent the designed system has reached the design goals. Many researchers have reported and evaluated the problems of drip irrigation systems in recent years. A research that evaluated drip irrigation systems in southwestern Okra, Nigeria, resulted that the volume of water given to the products was more than the water requirement of the plants and the efficiency of the system was %68.5. The other study examined various uniformity indices in drip irrigation systems in bamboo. The researchers concluded that due to the high sensitivity of the bamboo plant to the amount of received water and the distribution of moisture around it, the drip irrigation droplets with the flow rate of 4 lit/hr were more appropriate in compared with the 8 lit/hr. It could well meet the water needs of that plant. The purpose of this study is to evaluate the status of drip irrigation systems implemented in Dashtestan city to identify their strengths and weaknesses and provide suggested solutions to eliminate defects in the systems and improve their efficiency.
In this study, five drip irrigation systems in Dashtestan city were studied and evaluated. To evaluate drip irrigation systems in selected orchards, the proposed methods and formulas were used based on SCS standard and Merriam and Keller methods. Measurement of field evaluation factors included three steps: 1) Measurement of soil factors, 2) Determination the characteristics of the garden under study, 3) Measurement of hydraulic characteristics of irrigation system. A sample manifold was selected from each system, and the evaluations were performed on four laterals from the beginning, one third, two thirds, and end of the lateral. At each selected manifold, eight pressures were obtained at the beginning and end of the lateral tube, with 32 volumes of water at 16 trees. The average volumes of emitters and dispersion uniformity were calculated from the obtained volumes. The minimum input pressure of the sample manifold and the operating manifolds were also measured to determine the Efficiency Reduction Factor (ERF) and the DCF. After collecting data from field measurements using SCS and Merriam and Keller methods, evaluation factors such as water emission uniformity (EU), real low quadrant use efficiency (AELQ) and potential yield, the lower quadrant (PELQ) was calculated. The results showed that water distribution uniformity varied from 77.98% in M5 to 92.12% in M3. Low quadrant potential (PELQ) efficiency with 82.91 and 70.18% and true low quadrant use efficiency (AELQ) with values of 92.12 and 77.98% were obtained in M3 and M5 systems, respectively. The results indicated status of good to moderate in the systems. It was observed that when the farmer turned on the systems of M1, M2, and M5, they paid no attention to the water leaking out of the drippers, and did not remove them in cases of clogs or leaks from the connections. In the M5 system, due to the three-year of the filtration system, a highest pressure drop (3.9 m) was observed.
In general, the main problems of the systems in this study were: the low wetted area due to the inappropriate design and number of drops, the lack of proper placement of loop rings, the lack of uniformity of pressure distribution in the system, inappropriate wetted depth, the lack of uniformity of distribution of water, and the low knowledge and skill of the user. Due to the traditional irrigation system in Bushehr province and the high water demand of palms, about 70% of the water consumed in the agricultural sector was used for palm consumption. Therefore, it is necessary to pay attention to the improvement of palm irrigation methods in this province. According to assessment and measurements made in this study, drip irrigation systems would perform better if they were designed well to meet the plant's water requirements in a desirable way. The drip irrigation systems can create significant savings over traditional irrigation methods. Therefore, it is recommended to use more of these types of systems in this province. However, in some areas of the province, which have a source of salt water, some of drip irrigation systems have been clogged and out of use that require system improvement and operation training for farmers.