Evaluation of Extreme Scenarios of Climate Change on Discharge of the Shahid Rajaei Dam Catchment under HBV-light Model

Water management in water basins is difficult due to the lack of data collection stations. Today, rainfall-runoff simulations with different models will help manage existing water resources. Therefore, using hydrological models that allow the identification and management of the basin with minimal data can be a suitable method.

In this study, in order to simulate runoff caused by rainfall and to investigate the mechanism of runoff formation and outflow in the catchment area of the Shahid Rajaei Dam, located in Sari, the HBV-light model with existing data from 1981 to 2015 was used. Its performance was also evaluated under climate change conditions with two scenarios of RCP2.6 and RCP8.5 in the two time periods of near future (2016-2040) and distant future (2041-2065).

The results showed that the increase in temperature in the two scenarios of RCP2.6 and RCP8.5 by 11.5 and 13.9% in the near future and 13.9 and 24.2% in the distant future, respectively. Rainfall in the two climate scenarios RCP2.6 and RCP8.5 will also decrease by about 58% in the distant and near future. The output results of the model showed that the effect of climate scenarios on peak discharges will increase in the near future (2016-2040) and decrease in the distant future (2041-2065). The difference between the mean peak discharges in the future time window compared to the base period was significant at the 95% confidence level (Kruskal-Walli’s test). RCP2.6 and RCP8.5 will increase by 36% and 28% in the near future and decrease by 12% and 3% in the near future, respectively. These changes in peak discharges will increase the probability of occurrence of extreme phenomena (severe peak discharges) due to changes in the statistical distribution.

In general, these results indicate that the management, operation and maintenance of water resources accumulated at the site of the Shahid Rajaei Dam will face serious challenges. Therefore, it is suggested to apply advanced leading scenarios in catchment management while examining more closely and comparing with the results of other hydrological models.