عنوان مقاله [English]
Background and objectives: Paddy Fields Development and Renovation Project changes infrastructures of the rice farm management and converts traditional plot the plot irrigation system to water delivery management, which provides access to irrigation canals and drainage for each paddy plot. Even though many years have passed from the start of implementation of the project in northern provinces and several researchers have pointed fundamental problems out in the water distribution system of the project, but most previous studies have qualitative basis and the analysis is mainly based on the satisfaction of farmers or empirical judgments of experts in different parts of the project and until now less quantitative analysis has been provided on the basis of key performance indicators such as reliability indicating that ensure the delivery of agricultural water on time, to the extent necessary and for the time required and criteria such as dependability, steadiness, timeliness and predictability of the delivery of water provided by the researchers for its evaluation. Such indicators can measure the effectiveness of the system and finally it possible to provide planning, redesign and implementation of the corrective operation.
Materials and methods: In this study, reliability indices including the variability and predictability of water delivery system were calculated and compared for two concrete and earthen irrigation canals and the plots that are covered by them in renovated paddy fields of Esmaelkola village in Joybar city of Mazandaran province.
Results: The results of the quantitative indicators evaluation shows that although concrete lining of canal has made noticeable effect on the promotion of variability indicators in earthen channel, as Concrete channels have shown better results than earthen channel in the values of these parameters: Adequacy and dependability indices, respectively, 18 and 5 percent, fifty percent level of delivery reliability as 0.14, timeliness of water delivery as much as 4 days and delivery steadiness index as 0.27, but structural and managerial problems in intake and control system leading to inadequate and inequitable distribution of water between plots of lined channel according to the coefficient of variation 0.33 for adequacy and 0.46 for reliability and timely variations of water delivery to downstream plots show a major difference with defined standards considering steadiness lower than 0.5, timeliness index that was mostly more than 10 days and low amount of fifty percent level of delivery reliability. Both earthen and concrete channels linear correlation was mostly reversed between the delivered and required volume of water that indicates the lack of water delivery management based on demand. The inverse correlation coefficient between the variables of water delivery is -0.97 for concrete lined channel, so, it is correctly predicted improper management of water delivery in the final decades, and in the earthen channel, the value of 0.30 shows there is no correlation between the volume of delivered and required water and consequently low predictability of the system.
Conclusion: Generally, even with the concrete canal lining, indicators of reliable water delivery are not favorable in comparison with standards of these criteria. On the one hand, traditional, experience-oriented, and non-technical management system that governs water delivery in renovated farms has no appropriate scheduling for the use of supplied water during the planting season and on the other hand improving the existing system need to reform plots' intakes and flow control methods in the canal and complimentary water delivery schedule based on the irrigation demand.