JWSS - Journal of Water and Soil Science

Seepage losses and poor operational activities are the two main source of water losses throughout the agricultural water conveyance and distribution systems in irrigation districts. This study aims to investigate the performances of two strategies of “canal lining” and employing the “Canal Automation” in order to reduce the losses mentioned above. The investigation was carried out on a couple of main canal reaches of Moghan Irrigation Districts. Two numerical models were simulated by Seep/w software to compare the seepage rate between the canal with and without concrete lining. The results reveal that the ability of concrete lining to reduce seepage losses along the canal is about 10%. Performance assessment of the “Canal Automation” strategy to minimize operational losses within the main canal was carried out employing Model Predictive Control (MPC). The results of the latter strategy indicate that employing the MPC not only reduces the operational losses along the canal by 15% but also improves the operation of the main canal so that the minimum efficiency and adequacy performance indicator was obtained 100% and 83% respectively. Therefore; due to Executive considerations and financial constraints in the same cases, the potential of each of the two strategies can be considered to reduce the conveyance and distribution losses and ultimately choose the most suitable option.

This study focused on proposing a new operational perspective within main and lateral irrigation canals based on the economic value of water. To achieve this objective, the operation-economic framework offered in this study consisted of two main components of the PMP model and Operation model. The estimated economic values of water in different regions of the network were employed as the starting point for connecting the economic model with the operation model. It is worth mentioning that the technical perspective targeting adequacy of water distribution within the canals was modified in this study to be applied for the operation-economic framework since the original forms of the indicator were based on physical inherent of the water. Roodasht Irrigation District, located at Zayandeh-Rud basin, was selected as the case study, and the proposed framework was tested on the district. The obtained results revealed that in response to implementing the proposed framework in water distribution within the canal under the water shortage condition, alfalfa and safflower were the two crops those cultivation was decreased drastically in comparison with the other crops. The primary reason for the decrease was the lower values of the economic value of water for these two crops. Also ,the results of the canal operation appraisal from the adequacy of water delivery revealed that for the traditional operating system (without considering the economic perspective), the maximum values of the adequacy indicator were obtained for the upstream four canal reaches. On the other hand, the off-takes numbers of 1, 6, 5, and 12 got the maximum values of the adequacy indicator when the proposed operation-economic framework was applied for the canal system.

The main purpose of the study is the operational simulation of main irrigation canal and evaluation of water delivery and distribution locally, regionally and overall using adequacy, efficiency, and equity indicators and “Desirability of water delivery and distribution” indicator. To achieve this goal, the hydrodynamic model of Roodasht irrigation network’s main canal was developed. The results of the calibration and validation of the hydrodynamic model showed that the two processes were satisfactory. All available scenarios including normal, water shortages and fluctuations were considered for water delivery and distribution in different conditions. In the local assessment, the adequacy varied from 7 to 85%, and the efficiency in all scenarios was 100%. The adequacy, efficiency, and equity indicators in the regional evaluation varied from 6 to 89, 91 to 100, and 13 to 46%, respectively. The overall evaluation of the canal showed that the most desirable situation is related to a harsh fluctuation increasing with the adequacy, equity and efficiency indicators equal to 82, 23 and 91%, respectively. Calculation of the “Desirability of water delivery and distribution” indicator showed poor performance in all operational scenarios except harsh fluctuation scenario with 82% of which, the canal performance was estimated in fair level.