Drought evaluation over Yangtze River Basin based on weighted water storage deficit

Abstract The ability of Gravity Recovery and Climate Experiment (GRACE) to monitor large scale drought events has been explored well during past few years. We develop an alternative method viz.,weighted water storage deficit (WWSD) to characterize drought events over Yangtze river basin (YRB) based on water storage deficit (WSD) method by combining GRACE RL06 sphere harmonic (SH) coefficient data and WaterGAP Global Hydrology Model(WGHM) data.We use component contribution ratio (CCR) of single terrestrial water compartment as weight to compute WWSD, comparing with other commonly employed drought indices and precipitation data from Global Precipitation Measurement(GPM). The results show that precipitation is the major trigger of water storage variation over YRB, which both have significant seasonal change. Our findings also indicate different terrestrial water component contributes distinctly to terrestrial water storage (TWS) variability and responds differently to drought features in YRB according to water component storage deficit (WCSD). Eleven drought events are identified in YRB based on WWSD with 2003, 2006 and 2011 experiencing the severest drought with drought intensity of -1.22cm, -1.34cm and-1.02cm, respectively. Our study suggests that it is more realistic and reasonable to treat water components unequally to construct drought index derived from GRACE.