Risk Assessment of main transmission line in Irrigation Networks with Application of Fuzzy Hierarchical method

Background and objectives: Making an appropriate decision and providing solutions to improve the performance of irrigation networks require being aware of abilities and weakness of its components. This study initially identifies the upcoming treats, including natural, human-caused and operational hazards against the main water conveyance system in irrigation networks then presents a systematic framework assess the risk of irrigation network. Risk assessment method is widely used in the similar system such as urban water-supply system or wastewater collection, but so far it is not used in irrigation networks. This study at the first part has developed an integrated hierarchical such a way that it’s applicable for all of the irrigation districts considering different levels of operation and diversity of conveyance, regulation and delivery structures. At the second part assesses the risk of identified hazards.
Materials and methods: by doing library research, field study and interview with experts, treating hazards of each component are identified. Likelihood, consequences of treating hazards and vulnerability of component against the hazards are determined by using questionnaires, and the risk of the component is calculated. To deal with the uncertainty of expert’s opinion, the calculation is based on triangular fuzzy numbers, and finally, in order to make the results of the model tangible, fuzzy numbers transform to crisp numbers. To obtain the weight of the component, treating hazards, consequence criteria, and vulnerability criteria method of the fuzzy analytic hierarchical process was employed and to aggregate, the result of risk assessment the method of simple order weighted was conducted.
Results: the result of risk assessment revealed that at hazards level, the five riskiest hazard are: poor maintenance in the main canal with risk of 1.758, vandalism in Nyrpic module with risk of 1.6, poor maintenance in intersection structures with risk of 1.618, untrained operators’ error and inaccurate calibration in operation able gates with the risk of 1.54 and1.4. The result of risk aggregation according to hierarchical structure showed that in conveyance system among conveyance, regulation and delivery structures, the third one is the most critical structure with the risk of 1.966. Between two source of water supply, reservoir and well, the risk was obtained 1.274 and 0.99 respectively and indicated the criticality on the reservoir in compare with well. In the systems level conveyance system with the risk of 1.937 has the most risk. The result of model sensitivity analyses indicated that the change of overlap area in fuzzy membership, used in scoring stage, changed caused 1.2% and 2.12% change in decrease and increase mode respectively and the prioritization of the component and the riskiest hazards have no changes.
Conclusion: According to the founding of this research and determined risk value, hazards prioritization revealed that pain part of risky hazards generally categorized in hazards group which is related to the operation so concentration to an operation method and risk reduction of this threatening can bost the Reliability of system performance. Considering capability of the proposed model in determining the probability of hazard occurrence, multidimensional consequence and assessing the vulnerability of component against the hazards and also rectifying shortcomings of other conventional assessment methods applying the proposed model as a decision support method during management process and making decision recommended.