Assessing the impact of climate change on drought and forecasting Neka river basin runoff in future periods

In this study, the effects of climate change on runoff and SPI drought index in the Neka River basin in Mazandaran province were investigated. For this purpose, the data of the weather stations of Barikola, Pajim, Sefidchah, Glevard and Tirtash were used. Historical data of the Neka river discharge was obtained from Glevard hydrometeor Station. For this purpose, during the upcoming period (2018-2081), temperature and precipitation were simulated under three RCP2.6, RCP4.5 and RCP8.5 climate scenarios for the Neka river basin. To determine the mean value of climatic parameters of rainfall and temperature, the Thiessen interpolation method was used between meteorological stations. Then drought and runoff values were calculated. The IHACRES model was used to simulate runoff. The results showed that in all three climate scenarios, drought events will increase during the upcoming periods and wet and normal periods will decrease compared to the base period. Based on the findings, during the upcoming periods, the average annual flow of the Neka River under RCP2.6, RCP4.5, and RCP8.5 scenarios decrease between 17 and 44 percent. Thus, the average annual runoff volume of the Naka River at the Glevard dam will be reduced from 95 MCM in 2014 to 53 to 78 MCM. Therefore, in order to reducing the negative effects of the drought period and also reducing the flow of the Neka River, it is necessary to planning more accurate to avoid social, environmental, economic and cultural tensions.