Monitoring and Zoning of Drought in Southern Alborz

Drought is one of the most important natural hazards and often affects the lives of many people and causes economic damage, environmental damage and social problems. This study was conducted to evaluate the drought trend, intensity and duration during 1988-2019 in relation to the existing climates in the southern Alborz region. To describe droughts in 3, 6, 12 and 24-month time scales, two drought indices, namely standardized precipitation index (SPI) and standardized precipitation evapotranspiration index (SPEI) were used. In the case of SPEI, evapotranspiration was an important factor in monitoring drought. Therefore, (HS) method was used to calculate evapotranspiration. Drought intensity and duration maps were presented for SPI and SPEI. The correlation between SPI and SPEI was also examined. In the present results, unlike humid climates, SPI does not have a good correlation with SPEI in extremely arid and arid climates and shows the importance of reference evapotranspiration (ET0) to identify drought in these areas and the index (SPEI) has more accurate monitoring results. Relative to the index (SPI). In addition, drought intensity maps for (SPI) and (SPEI) have shown that the region is experiencing very dry conditions and water resources are affected by intense drought in the short and medium term. Short-term drought in the east of the region (Zanjan) and long-term drought in the center and west of the region (Garmsar, Semnan, Karaj, Tehran) have been more.