5 CONCLUSIONS
A method of monthly AET simulation using public satellite precipitation and TWS data was proposed utilizing the hydrologic budget within a closed inland basin. As these data are available at a global scale, the method may easily be applied to simulate monthly AET in other closed inland basins. In addition, trends in annual and monthly precipitation, TWS, and AET were detected using the MK test. The main attributions of AET and TWSA changes were identified for the EIB and each of its closed basins.
There was a slightly increasing trend in the annual precipitation of the EIB for 2002–2020, with a magnitude of 3.7 mm /10a. A decreasing trend was detected in the western and northern basins, including the BLB, CSB, IIRB, JB, QPB, and TuRB. The highest increasing and decreasing magnitude was 52.3 and -20.4 mm/10a in the HRB and IIRB, accounting for 28.6% and 10.8% of the mean annual precipitation, respectively; all these trends were non-significant. In the EIB and most of its closed basins, the TWSA and AET showed significant decreasing and non-significant increasing trends, respectively. The increasing trends of the TWSA were mainly detected at the Qinghai-Tibetan Plateau, including the QB (significant) and QPB, and some headwater regions.
The increasing AET water consumption was the dominant factor affecting the significant decrease in TWSA in the EIB. The consumption of other water sources, mainly included irrigation diversion and glacial melt runoff, accounted for 70% of the increasing AET. At the basin scale, changes in the AET were the main factor impacting changes in the TWSA in most basins, including the ASB, CSB, GHCB, HRB, IMPB, ISB, JB, MPLB, MPIRB, QPB, TaRB, and TB. Changes in precipitation played a dominant role in changes for the TWSA in the BLB, IIRB, QB, and TuRB. Similar to the EIB, the consumption of other water resources was the main factor driving the changes in the AET for the ASB, CSB, JB, MPLB, MPIRB, QPB, and TaRB. However, the precipitation increase contributed >60% to the elevated AET in the HRB, QB, GHCB, and TB, particularly in the former two basins, where the contribution exceeded 90%. Changes in precipitation and the consumption of other water sources contributed approximately half of the AET changes in the IMPB, ISB, BLB, IIRB, and TuRB.