Nash Bargaining Optimization of Released Water from a Reservoir Dam under Climate Change Conditions (Case Study: Doiraj Dam)

There is a growing demand for solving conflicts among water users and stakeholders under climate change conditions. This study applied ten CMIP5 climate models under the RCP8.5 scenario to simulate Doiraj Reservoir water allocation in Ilam Province. To reduce the uncertainty of climate models, the MOTP method was used by combining different GCM models. To predict reservoir inflow, the IHACRES Rainfall-Runoff model was considered and validated for the 2016 to 2044 time periods. Climate and hydrological indicators were extracted to monitor drought periods in the current and future projections. The WEAP model and the Asymmetric NASH Bargaining Method were used to simulate the water basin system and solve the conflict between stakeholders based on their utility functions, respectively. The results indicated that the rainfall would increase by 17.1 and 11.1% in spring and autumn and decrease by 9.4% in winter in the future projection. Furthermore, the highest temperature and runoff growth rate increased by 1.95°C in September and 6.3% compared to the base period, while demands would be increased by 55.75%. The long-term agricultural deficit are obtained as 10.9 and 10.2% by the WEAP model in the current and future conditions. Finally, the duration curve of reservoir storage showed that 20% of the time, the reservoir storage is empty for the Standard Operation Policy (SOP). By switching to the Nash bargaining policy, not only the minimum storage capacity reached 18 MCM for all the time, but also the effects of climate change would be adapted in the future, and the utility functions of all stakeholders would be satisfied as well.