INVESTIGATION OF THE CORRELATION BETWEEN GRACE TWS AND SOIL MOISTURE IN SARAKHS CATCHMENT

Abstract. Drought is a gradual phenomenon that may intensify with time. In fact, drought is the result of interactions between natural and human activities and usually appears in the following ways: reduction in water resources, accelerating desertification, the vegetation cover change and etc. Monitoring and predicting drought is essential for sustainable water management and mitigating socio-economic damages. The GRACE satellite mission provided monthly Earth’s gravity field anomalies, which can be processed to obtain changes in Total Water Storage (TWS) content. TWS is a sum total of various compartments of water near the surface of the Earth, such as soil moisture, surface water, snow, etc. In this study, we analyze GRACE TWS and the modelled soil moisture (SM) over Sarakhs catchment in north-east of Iran, between 2003–2016. We find a time lag of 19 months between GRACE TWS and soil moisture, where both TWS and soil moisture content show negative trend over Sarakhs catchment. Our findings are similar to other reports on the water scarcity in this region.