Selection of best water allocation scenario in Karoon watershed using social choice approaches

Water shortage in Iran is one of the main limiting factors for development of economic activities in the coming decades. The multitude of stakeholders and differences in opinions on how best to exploit the available resources commonly lead to conflicts and disputes over the management of watersheds and river basins. A main concern in water resources management is the equitable allocation of water. Conflicts on water rights are not solely limited to economic benefits or costs, but they involve social and political issues as well. In addition to this issue, conflicts arise between stakeholders who use water for a variety of consumptions, such as potation, industry, agriculture and environment. Karoon watershed can be an example of unbalanced demand and supply that the water shortage and losses and environmental problems are the main concerns of the watershed. Hence, to achieve a relative balance in the supply of water is essential and necessary.
The water allocation for Karoon watershed with an area of 67257 km2 located in the western part of Iran is considered based on the conflict resolution approach. There are 6 provinces claim on water resources of the watershed that are Lorestan, Chaharmahal and Bakhtiari, Kohgiluye andBouyer-Ahmad, Isfahan, Markazi and Khouzestan as the stakeholders of the watershed. In order to simulate and manage the water resources of watershed, MODSIM model has been implemented. The foundation of modelling is set on configuration of watersheds which are shaped by links (streamflows and rivers) and nodes (reservoirs, consumption). The MODSIM model is developed to simulate the watershed under seven different scenarios. There are several factors which are considered for definition of different scenarios such as improving the cropping pattern, utilization of drainage and water transition networks, climate changes, environmental issues and improving industry and agriculture. Different methods based on conflict resolution approach, including the social choice and Fallback Bargaining are utilized to select the best scenario. Decision making in the social choice method depends on stakeholders’ votes or opinions. Social resolution is concluded by a voting process and the best alternative will be presented by the majority of the stakeholders’ votes. Three methods such as Condorcet, Borda scoring and median vote rule are subset of social choice approach are selected for the following study. Fallback Bargaining follows the reversible or iterative process for negotiations and bargaining to find the optimum alternative. The process is continued until the minimum utility or satisfaction is expressed by the stakeholders. Also the stability index was used to evaluate and select the best scenario with minimum inequality among stakeholders. In this evaluation method, unlike in the other methods described, alternatives (scenarios) are compared in terms of their degree of stakeholders’ satisfaction or the associated inequities.
In order to evaluate scenarios, they have been compared by implementing above criteria. The Scenario 4 with a score of 7 by the Condorcet method in which the couple competition that occurs between alternatives is in priority rather than others. Scenarios 2 and 5 were in second and third ranks, respectively. By using the Borda Scoring method, stakeholders grade the scenarios based on their benefits and the scenario 4 earn maximum score equal to 44 that was rated as the best case scenario. The other criteria of social choice are the median voting rule. If the answer of median voting rule is obtaining minimum 4 votes, scenario 4, 2 and 5 are in priority, respectively. Also based on the Fallback Bargaining method which follows the iterative procedure to set stakeholders’ minimum satisfaction scenario 4 was selected as the best option. Stability index has a different view than other approaches. This method searches stable alternative instead of stakeholders’ opinions, even though scenario 4 with the stability index of 1.18 is the best answer. This scenario with the lowest value indicates the minimum level of dissatisfaction among stakeholders compared to other scenarios. The selected scenario is including the execution of under study projects along with demand management and aquifer restoration count as proper management options. By evaluating the deficit of groundwater reservoirs, the maximum value belongs to scenario 0 and 1 with a value of 35 million cubic meters while this value is decreased to zero by using scenario 4. Water allocation under a policy of scenario 4 will be stable for Karoon watershed as a case study and majority of stakeholders will vote on selected scenario who benefit from water as industrial, agricultural and domestic consumers.