Forecasting and investigating the trend of rainfall changes and its effects on meteorological drought in the south of Aras River basin

Drought is a natural and repeatable phenomenon that occurs due to a decrease in the amount of rainfall in a certain period. In the current research, the trend of rainfall changes and meteorological drought forecasting of 6 stations located in the Aras watershed have been investigated. To evaluate the severity of the drought, the annual rainfall data of the stations in the statistical period (1987-2021) was checked using the Standardized Precipitation Index (SPI) and simulated using MA, AR, ARMA, and ARIMA time series rainfall models and based on the criteria (AIC) was chosen as the best model for prediction. ARIMA model (0,0,1) was selected for Ardabil, Khoy, and Ahar stations, and the AR model (0, 0, 1) was selected for Parsabad, Maku, and Jolfa stations as the models with the best results. The forecast results for the next 5 years show an increase in rainfall, which makes the results of the fitted models acceptable based on the rainfall statistics available in the respective years. The results of the trend index (SPI) also showed that all 6 stations are close to normal and the highest severity of severe drought is related to Khoy station with 14%. Maku station also observed average wet conditions with 6% frequency during the studied period. Also, the results of precipitation changes using the Sen s slope test show a significant increase in precipitation in Maku station an increase without a trend in Parsabad, Khoy, and Jolfa stations, and a decrease without a trend in Ardabil and Ahar stations.