Application of GRACE Satellite Observations in Drought Monitoring (Case Study: Markazi Basin, IRAN)

Drought monitoring is one of the main pillars of drought management. Therefore, investigators are always looking for a way to improve the drought monitoring accuracy. The main purpose of this paper is to investigate the efficiency of GRACE satellite observations in drought monitoring in the Markazi basin of Iran between 2002 and 2016. With the launch of this satellite, it has been possible to monitor total water storage anomalies (TWSA) for the entire world with high precision. Due to the significance of human activities impact on Total Water Storage Anomaly (TWSA), obtained from GRACE in the above mentioned basin, the common GRACE-based drought indices, such as Drought Severity Index (DSI), has not been efficient in this basin. Therefore, in this paper the newly Modified Drought Severity Index (MDSI) is introduced based on de-trended TWSA time series. Also, both Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI) were used, as the criteria to assess the performance of DSI and MDSI. The results showed that the correlation coefficient between DSI and SPI12/SPEI12 were equal to 0.42/0.26, while these values for MDSI were equal to 0.69 and 0.56, respectively. Calculated MDSI time series revealed that during the studied period, the most severe and longest drought occurred in the years 2008-09. During this period the basin faced with a deficit of 238 km3. On the basis of maximum and average rate of deficit changes in the basin, at least 21 and on average 91 months is needed for recovery of this deficit.