Optimal Allocation of Surface Storage Tanks Using Fuzzy Hierarchy Method(Case Study: Shahrchay Storage Dam in Urmia)

Prioritization of optimal water allocation of surface flow storage dams for different applications (drinking, agriculture, industry, environment, etc.) in arid and semi-arid regions such as Iran due to the range of changes, high flow uncertainty Reservoir inlets, and the occurrence of intermittent droughts are of great importance. For this purpose, the Fuzzy Hierarchy Process (FAHP) is proposed and used as a suitable formulation method in prioritizing water allocation in the water resources system. Therefore, in this study, prioritization of water allocation for different purposes of Shahrchai reservoir dam located upstream of Urmia metropolis has been done in a field study using fuzzy hierarchical method.

A fuzzy hierarchical process based on quantitative and qualitative effective factors has been developed. In the first stage, the problem structure was designed by determining the priority of water allocation of users, criteria, sub-criteria, and other factors. Then the decision-making hierarchy based on the problem structure (purpose, criteria, sub-criteria, factors, and options in the first to fifth levels, respectively) was defined. In the mentioned prioritization structure, the goal was determined at the first level, ie the optimal or appropriate allocation of Shahrchay reservoir dam water for different operators, and at the second level, three economic, social and environmental criteria were considered as the main criteria. At the third level, " cultivation area and gross income" and "employment and population" were considered as sub-criteria of two economic and social criteria, respectively. The main beneficiaries, namely agriculture, urban drinking, recreation and tourism, industry, environmental needs of Lake Urmia and groundwater fourth level (options) have formed the problem structure. At the next step, based on the field data or questionnaires, criteria, sub-criteria, and factors were compared in pairs using the proposed linguistic and fuzzy comparisons, and the priority of water consumption over each criterion or sub-criterion or factor were compared based on fuzzy triangular numbers. The weights were determined and ranked each using the Chang development method. At the third stage of the final ranking, the priority of water allocation was determined based on the final weight of criteria or priorities at the previous stage and the superior option was determined. Finally, a sensitivity analysis of the weight change of the criteria and the decision-making process of the problem has been performed.

A decision model based on a fuzzy approach is presented to rank the different options using Shahrchay dam water. For this purpose, firstly, using the opinions of experts and researchers, the results of a questionnaire, criteria and sub-criteria and important options in allocating water to Shahrchai Dam were determined. Secondly, using Chang's development analysis, different options were evaluated based on the mentioned criteria, sub-criteria, and factors. From a scientific point of view, because the questionnaires were presented to experts, the economic criterion is a high priority, so it is possible to attach great importance to the general conclusion about the criteria in economic attitudes and related issues. In addition, the allocation of water to the urban drinking sector with a weight of 0.33 was as the top priority, agriculture, Lake Urmia, industry, groundwater, and recreation were in the next priorities, respectively. Therefore, economic criteria and drinking water supply were recognized as the main objectives of planning and managing water resources in the metropolis of Urmia. The drinking sector is a vital factor for the survival of a community and because the drinking water of Urmia city is supplied through Shahrchai dam, so the allocation of water to this sector should be considered as the top priority. The agricultural sector was also given the second priority with less importance. The supply of water to this sector has a significant direct effect on the economy of the agricultural sector and indirectly on the entire economy of the region, which indicates the importance of the agricultural sector in the economy, living conditions of the region and the allocation of water to this sector. Comparing agricultural and industrial activities in Shahrchai catchment area, the most activity in the region is agriculture and industry is in a lower priority, which is also shown by the hierarchical results. Since Shahrchai River is one of the suppliers of water to Lake Urmia, the allocation of water to this section improves the condition of the lake and, consequently, it improves the environmental, economic, and social conditions of the region. The results also indicate the importance of Lake Urmia in relation to industry and its higher status indicates the attention of officials to the drying crisis of the Lake Urmia.