Investigation of the Hydrological Response to Meteorological Drought in Kashkan Sub-Catchments

The meteorological drought phenomenon and its relationship to the hydrological response of the catchments are of particular importance in the development of programs related to the comprehensive water management of the basin. In this study, a common period (1982-2017) in five corresponding hydrometric and rainfall stations in the Kashkan watershed was considered. The regression relationship between rainfall and discharge was investigated. Then, the standardized precipitation index (SPI) and the standardized discharge index (SDI) were calculated in time scales of 3, 6, 9, 12, 18, and 24 months. The interrelationships of SPI and SDI in sub- catchments were analyzed using the correlation method. The results showed that in more than 50% of the study period, the meteorological drought was close to normal. hydrological drought investigation of the sub-catchments showed that in the catchments with fewer karst formations, the frequency of years with severe drought was higher. The maximum drought with a severe situation in the Afrine catchment was 20% and the minimum was 6% in the Cham-Anjir catchment. The trend of changes in correlation coefficients between SPI and SDI in Sarab- Seyed Ali, Pol-e Dokhtar, and Cham-Anjir were similar and the maximum was at 18- and 24-month time scale with a coefficient determination of 0.67.