Abstract
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.
Highlights
The hazard of drought is a complicated and a gradual phenomenon
The results indicate that there is an agreement between GRACE Total Water Storage (TWS) and soil moisture over Sarakhs (61.11%)
The occurrence of drought depends on several factors that can differ for various catchments, including reduced precipitation, increased evapotranspiration, anthropogenic activities and etc
Summary
The hazard of drought is a complicated and a gradual phenomenon. Drought can be categorized according to meteorological, hydrological and agricultural types [12]. Soil moisture observation is not readily available in our region of interest, we rely on a Land Surface Model: Global Land Data Assimilation System (GLDAS). It is forced by satellite observations and observation driven reanalysis data to yield gridded product with a spatial resolution of 0.25 degrees. Changes of the different components, including surface storage, soil moisture and groundwater can create important changes in local climate, water supply sources and agricultural production. We compare the GRACE total water storage data and soil moisture component simulated by GLDAS model. We obtained that soil moisture variations 19 months ahead of GRACE TWS somehow means agricultural drought happened much earlier than hydrological drought in this specific region
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