Determining Qualitative-Quantitative Optimal Exploitation Policies of the Dam Reservoir by Combining the Decision-making Model Based on Fuzzy Logic and Game Theory: A Case Study of the 15 Khordad Dam

Given the limited water resources and quality problems of dam reservoirs, as well as the presence of multiple decision makers with conflicting desirability and goals, the very important issue for dam reservoir operators, is deciding on determining the average monthly water withdrawal, so that the needs of all stakeholders and decision makers are met. In this research, by combining the ELECTRE I multi-criteria fuzzy decision model and the RUBINSTEIN bilateral bargaining model, a new method for determining the optimal amount of quantitative-qualitative allocation of dam reservoir water is presented with the aim of increasing the desirability of decision makers and reducing tension between them. By identifying the expert decision-making beneficiary in the operation of the dam reservoir and determining their desirability at first, priority of the optimal points on the quantitative and qualitative exchange curve, presented by previous researchers, are determined in this study from the perspective of each beneficiary and according to the five different quantitative, qualitative, economic, social and environmental indicators. This exchange curve obtained by an algorithm combining a multi-objective genetic algorithm (GA)-based optimization model and a one-dimensional water quality simulation model (WQRRS) is merely the output of a mathematical model and practically does not satisfy the stakeholders’ utilities. The point they agree on the trade-off curve, is analyzed then, using the game theory. The RUBINSTEIN bilateral bargaining model is developed to determine the point agreed between the decision’s makers on the exchange curve. Due to the use of a fuzzy-logic based decision-making approach and considering different criteria, the utility of all decision makers was close to each other and the scope of bargaining became smaller, leading to an increase in the possibility of reaching an agreement in a shorter time period using game theory. All qualitative judgments without considering explicitness of the decision makers were applied to the model using the fuzzy logic. In the proposed method, the opinions of decision makers were considered according to different criteria in the operation of the dam reservoir. Because the decision makers considered different criteria in addition to quantitative and qualitative criteria, they were willing to participate in bargaining and reconsider their ideals. The results of the analysis show that the preferences of each decision maker are closer to each other and the chances of reaching an agreement in a shorter time increase in practice, using the game theory. Here, the 15-Khordad Dam located in the central part of Iran, suffering from low water quality, was studied in order to evaluate the effectiveness of the model. The 15- Khordad Dam with 54 meters elevation above the riverbed is located at the upstream of Ghomrood river basin in the central part of Iran near the cities of Delijan and Mahallat. The dam is used to capture the runoff from the Ghomrood watershed for agricultural irrigation use of more than 8,000 hectares, water supply to the city of Ghom, as well as for flood and sediment control. “Salinity” or “Total Dissolved Solids” (TDS) are the most important problems of this dam. Identifying the organizations with an active interest in the operation of the 15- Khordad dam is the first step in the assessment of stakeholder’s situation. The two major stakeholders that represent various organizations and sub-divisions are the Ministry of Agriculture (Ag) and Urban Water Organization (Ur). Ag allocates a very large amount of water to irrigation and agricultural land. According to the policy of this organization, the quantity of water is more significant than its quality, while Ur should pay attention to the quality of the water for urban water supply as well as its quantity. The results of applying the proposed integrated method for operation of 15 Khordad dam reservoir in Iran over a 30-year statistical period (1968-97), indicate the possibility of agreement on a monthly water allocation with the quality of TDS = 1580 mg /L, according to the criteria of decision makers and reduction of differences between them. The data of 15- Khordad dam for a 30-year time interval were collected by Shirangi et al. (2008). In the proposed methodology, given the conditions and uncertainties available, the ground has been provided for all decision-makers to determine the best possible strategies so that they can bring the most benefit to them in the negotiation space. Using this framework, disputes between decision-makers and stakeholders are sharply reduced and can be very useful in modeling the negotiations.