The main causes of changes in actual evapotranspiration and terrestrial
water storage over the Eurasia inland basin
Abstract
The climate of the Eurasia inland basin (EIB) is characterized by
limited precipitation and high potential evapotranspiration; as such,
water storage in the EIB is vulnerable to global warming and human
activities. There is increasing evidence pointing to varying trends in
water storage across different regions; however, a consistent conclusion
on the main attributes of these trends is lacking. Based on the
hydrological budget in a closed inland basin, the main attributes of
changes in actual evapotranspiration (AET) and terrestrial water storage
(TWS) were identified for the EIB and each closed basin. In the EIB and
most of its closed basins, the TWS and AET showed significantly
decreasing and non-significantly increasing trends, respectively. The
primary cause underpinning the significantly decreasing TWS in the EIB
was increasing AET. Approximately 70% of the increase in AET has been
supplied by increased irrigation diversions and glacial melt runoff. At
the basin scale, similar to the EIB, changes in AET were the predominant
factor driving changes in TWS in most basins; the exception to this was
the Balkhash Lake basin (BLB), Iran inland river basin (IIRB), Qaidam
basin (QB), and Turgay River basin (TuRB). In these basins, changes in
precipitation largely contributed to the TWS changes. The AET
consumption of other water resources was the main factor contributing to
AET changes in seven of 16 basins, including the Aral Sea, Caspian Sea,
Junggar, Monglia Plateau, Qiangtang Plateau, and Tarim River basins. The
increase in precipitation contributed more than 60% of increasing AET
in four of 16 basins, particularly in the Helmand River basin and QB
(>90%). Changes in precipitation and consumption by other
water supply sources contributed to approximately half of the AET
changes in the other five basins, including the Inner Mongolia Plateau,
Issyk-Kul Sarysu, BLB, IIRB, and TuRB basins.