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Terrestrial water storage (TWS) is an essential element of the water cycle and a key state variable for land surface–atmosphere interaction. This study investigates the changes of TWS in Xinjiang of China in response to climate change, using Gravity Recovery and Climate Experiment (GRACE)-derived data and ground hydrological/meteorological observations in 2003–2015. The results show that the TWS has an overall significant decreasing trend of −2.8 mm per year. TWS is in a state of surplus in the first half year (from February to July), while it is in a state of deficit in the second half year (from August to next January). The change rates in TWS exhibit strong regional disparities, with profound decreasing trends in Tianshan Mountains and increasing in Kunlun Mountains. Further analyses suggest that the spatial-temporal change of TWS was closely related to the variations in seasonal snow melt and glacier retreat due to temperature and precipitation changes. [ABSTRACT FROM AUTHOR]

• Significantly decreasing trend of GRACE is observed which indicates the serious terrestrial water depletion. • Soil moisture and runoff have significant decreasing linear trends in Aral Sea Basin. • Precipitation is the major climate factor positively impacting on the terrestrial water cycle components. Assessments of the regional terrestrial water variabilities are important for improving our knowledges of the complex hydroclimate system and providing scientific information in regional water resource management under a changing environment due to climate change and intensified human activities. The Aral Sea Basin has experienced a serious ecological crisis which is majorly caused by the water resources due to the excessive water utilization. Therefore, in this study, we examine the long-term linear trend and variability of the terrestrial water cycle components based on multiple datasets over the Aral Sea Basin during 2003–2016. The terrestrial water cycle components include precipitation, evapotranspiration (ET), terrestrial water storage anomaly (TWSA), terrestrial water storage change (TWSC), runoff (R), soil moisture (SM) and groundwater. Major results show that increased trends of the annual precipitation and ET are observed during 2003–2016. For TWSA, Gravity Recovery and Climate Experiment (GRACE) derived datasets have significantly decreased trends with the values from −0.47 mm/mon to −0.29 mm/mon which reveal the serious terrestrial water depletion. Runoff, soil moisture and groundwater have the decreasing linear trends derived from multiple datasets. For the impacts of the climate factors on TWSA and TWSC, precipitation is the main climate factor with the significantly positive impacts. These results help us to have a better understanding of the complex hydrological process over the Aral Sea Basin, and provide a reliable scientific basic for police maker in the water resource management to achieve a sustainable development goal over the regions of the One Belt and One Road. [ABSTRACT FROM AUTHOR]

• Declining water storage trends in the GRACE and GHMs were observed over Central Asia. • TWSA can be well simulated and predicted by climate variables. • Potential strategies are provided to address the SDGs of water resource over Central Asia. Arid regions of Central Asia have sensitive ecosystems that rely heavily on terrestrial water storage which is composed of surface water storage, soil moisture storage and groundwater storage. Therefore, we employed three Gravity Recovery and Climate Experiment (GRACE) satellite datasets and five global hydrological models (GHMs) to explore the terrestrial water storage (TWS) changes over arid regions of Central Asia from 2003 to 2014. We observed significantly decreasing water storage trends in the GRACE data, which were underestimated by the GHMs. After averaging the three GRACE satellite datasets, we found that the water storage was decreasing at a rate of −4.74 mm/year. Contrary to the prevailing declining water storage trends, northeastern Kazakhstan (KAZ), and southern Xinjiang increased their water storage over the same period. The GRACE data showed that Turkmenistan (TKM), Uzbekistan (UZB) and KAZ experienced the most severe water depletions, while Tajikistan (TJK) and northwest China (NW) experienced the least significant depletions. With respect to the major river and lake basins, the Aral Sea Basin exhibited the most serious water loss (-0.60 mm/month to −0.38 mm/month). The water storage positively correlates with the precipitation; and negatively correlates, with a three-month lag, with temperature and potential evapotranspiration (PET). Partial least square regression (PLSR) had the high capability in simulating and predicting the TWS. These results provide scientific evidence and guidance for local policy makers working toward sustainable water resource management, and the resolution of international water resource disputes among Central Asian countries. [ABSTRACT FROM AUTHOR]

Under climate change and increasing water demands, groundwater depletion has become regional and global threats for water security, which is an indispensable target to achieving sustainable developments of human society and ecosystems, especially in arid and semiarid regions where groundwater is a major water source. In this study, groundwater depletion of 2003–2016 over Xinjiang in China, a typical arid region of Central Asia, is assessed using the gravity recovery and climate experiment (GRACE) satellite and the global land data assimilation system (GLDAS) datasets. In the transition of a warm-dry to a warm-wet climate in Xinjiang, increases in precipitation, soil moisture and snow water equivalent are detected, while GRACE-based groundwater storage anomalies (GWSA) exhibit significant decreasing trends with rates between-3.61 ± 0.85 mm/a of CSR-GWSA and −3.10 ± 0.91 mm/a of JPL-GWSA. Groundwater depletion is more severe in autumn and winter. The decreases in GRACE-based GWSA are in a good agreement with the groundwater statistics collected from local authorities. However, at the same time, groundwater abstraction in Xinjiang doubled, and the water supplies get more dependent on groundwater. The magnitude of groundwater depletion is about that of annual groundwater abstraction, suggesting that scientific exploitation of groundwater is the key to ensure the sustainability of freshwater withdrawals and supplies. Furthermore, GWSA changes can be well estimated by the partial least square regression (PLSR) method based on inputs of climate data. Therefore, GRACE observations provide a feasible approach for local policy makers to monitor and forecast groundwater changes to control groundwater depletion. [ABSTRACT FROM AUTHOR]