Improvement of Maintenance Process of Offtake Structures in Irrigation Canals Based on Monitoring and Analyzing of the Current Situation(Case Study of Northern Behbahan Irrigation Scheme)

Unlike industrial facilities, irrigation and drainage infrastructure are both scattered and expensive compared to the revenues of irrigation management organizations. Also, these assets (canals and structures network) have specific hydraulic properties in terms of their function and role. Since irrigation organizations must also consider the commercial aspects of irrigation and drainage services, it is necessary to consider the details of the costs incurred in providing these services. Each service and facility must be managed based on its durability and life cycle to provide the services at the lowest cost. Maintenance extends the life of the equipment and in other words delays depreciation and failing. Maintenance plays an important role in the reliability, quality of production, risk reduction and increased efficiency. In the present situation, the lack of anticipation of structures failing, and its timely maintenance in most irrigation networks, reduces the life of network components, which is a major investment for them. Therefore, in this study, using the existing relationships and criteria and using statistics and probabilities, in addition to assessing the maintenance status of offtake structures in Behbahan irrigation network, the failure pattern of structures is predicted using maintenance scenarios. Then, the research results are presented for timely planning and repairs to reduce the risk of failure and reduce the costs imposed on the studied structures.

In this study, the status of the off take structures along the canal path in the northern Behbahan irrigation network on the right bank of the Shohada diversion dam has been studied. The off take structures in the Behbahan irrigation network are used to adjust the amount of water flowing into the canals to coordinate the water level and the flow rate with the amount of water demand. The network has one main canal (about 20 kilometers long) that supplies water to the second channel, A1 to A12. Many maintenance issues such as failure times are not accurate. Many of the factors in these systems are random. But it is possible to define them as random variables and assign them probabilistic distributions. To improve the maintenance condition, a maintenance program should be used that not only reduces operating and maintenance costs but also reduces the risk of failure. Therefore, three scenarios including low reliability, high reliability, and current maintenance conditions are defined.

Since it is impossible to achieve the conditions of a structure to its initial conditions, it is therefore assumed the target of reliability is 90%. To compare the scenarios in terms of maintenance costs, the cost of each scenario is calculated. The cost of repair in the S1 scenario(a current condition in the present network) is higher than the other two scenarios, with approximately 1.7 times the S2 scenario and 2 times the S3 scenario. Therefore, the north of Behbahan network is not in favor of maintenance. On the other hand, the S3 scenario is better than the S2 scenario because it will reduce costs by 20%. The results show that in order to reduce maintenance costs, structures in an irrigation network must be monitored on a continuous basis and be inspected regularly (not at the time of failure). Maintenance of the Behbahan irrigation network is done only at the time of failure and therefore costs are high to maintain the network. Improving maintenance and planning for monitoring structures in the irrigation network will reduce failure rates, increase reliability, and reduce operating and maintenance costs.

Asset monitoring alerts management to the status of assets and enables it to plan and act on any asset and its role in providing services. Also, asset status information and statistics are used as an indicator for prioritizing costs and investments and scheduling them. In this study, using repair and maintenance statistics of offtake structures in the North of Behbahan irrigation network, their physical status, and probability of failure were evaluated and based on the maintenance scenarios, solutions were provided to maintain and increase performance, reduce costs and increase their reliability. The results show that predicting the failure time of the structures and their timely maintenance not only reduces the failure rate but also reduces maintenance costs. Although periodic maintenance (not only at breakdown time), although it increases the frequency of repairs, due to the low cost of repairs, it not only reduces the cost of the entire network by 20% to 100% but also increases the reliability of the structure's performance. And it reduces its failure rate by 20 to 80 percent.