Future droughts in China using the standardized precipitation evapotranspiration index (SPEI) under multi-spatial scales

The future changes in water resources are essential for water resources management and agricultural production in the context of climate change. In this paper, by adopting five global models, the standardized precipitation evapotranspiration index (SPEI) was utilized to character the dry conditions during 2020–2099. The Mann-Kendall test with trend-free prewhitening (TFPW-MK) was used to detect the change trends of SPEI and drought characteristics were predicted at both national and regional scale. Results showed that there is a large difference in the frequency of dry and wet occurrences at different time scales. The 12-month SPEI has a stable alternate between dry and wet occurrences, and a long duration of drought, which better describe the annual changes of drought influencing the streamflow and reservoirs. It is obvious that the available water resources decrease over time under the RCP 8.5 scenario. The TFPW-MK test indicated that southwest China have an upward trend in SPEI, while northwest, northeast and southeast China shows a drying trend. From a national perspective, water resources are relatively abundant in the future under the RCP 4.5 scenario, which is beneficial in terms of utilization of future water resources. In the long term, the northwest and northeast China have longer duration and stronger intensity of drought than those in other areas. In a high level of radiative forcing, the available water resources decrease obviously, and thus the occurrences of dry event increases. In addition, the abnormal dry events mainly appear after 2070, principally in GXR and LPR. These results can provide reference for drought warning in agricultural production, and meanwhile is beneficial for allocation and rational utilization of water resources.