Evaluating the Effect of Climate Changes on Runoff and Maximum Flood Discharge in the Dry Area (Case Study: Tehran-Karaj Basin)

The aim of this study was to the prediction and analysis of temporal pattern changes of runoff, maximum discharge, and Drought indexes in the Tehran-Karaj basin.

In this study, the temperature and precipitation data extracted from Statistical Downscaling Model (SDSM; 2021-2050 and 2051-2080) together with observational runoff data of the Sulghan hydrometric station (1986-2015) were used as input data for IHACRES rainfall-runoff model and discharge rate, runoff volume, and maximum discharge were extracted in the desired scales. Then, drought indexes (SPEI and SRI) were investigated.

In the period of 2021-2050 and 2051-2080, the mean of annual discharge, volume of runoff and annual precipitation will be decreased. While seasonal runoff, discharge, and precipitation will rise in the winter. Moreover, the maximum predicted discharge (In most scenarios) in the return periods less than 5 and more than 50 years is less than the observation period and in the Return Periods of 5 to 50 years it will be more than the observation period. Besides, 48-month SPEI with 48-month SRI (without delay) has a maximum correlation with each other at the level of 99%.

In the winter season and return periods of 5 to 50 years, the floods hazards and Rivers overflow in the Future periods (2021-2080) will be more than the observation period. Also, meteorological droughts often have their effect on the drought of surface waters during the same month.