Assessing the recent droughts in Southwestern China using satellite gravimetry

Heavy droughts have frequently struck Southwestern China in recent years. A major consequence of these droughts is the loss of terrestrial water storage (TWS) which affects agriculture, civil life, and industry production and results in serious social and economic losses. The satellite gravimetry has been proved an effective way to estimate hydrological variations over the globe, and we use the monthly gravity solutions from the Gravity Recovery and Climate Experiment (GRACE) satellite mission and extract the hydrological variations from the regional gravity signal. Here we show that the recent heavy droughts in Southwestern China have caused observable nonseasonal gravity changes in the monthly GRACE solutions. Two heavy droughts in September 2009 to May 2010 and August 2011 to January 2012 have resulted in significant TWS deficit up to hundreds of gigatons in Southwestern China. It is found that the latter drought in 2011-2012 is the most severe one in Southwestern China over the decade, hitting large areas, and causing heavy TWS deficit. Affected by the recent droughts, the GRACE estimate shows a gradual decrease in the regional TWS during the recent 4 years in Southwestern China with a nominal rate of -13.37.5 mm/yr, which indicates the severity of the TWS deficit in this area.