Spatiotemporal characteristics of drought in the Nanpan River Basin, Yunnan Province, China, from 1956 to 2016

Abstract

Abstract Investigating the spatiotemporal characteristics of drought is crucial for developing effective water resource and drought risk management strategies throughout basins. In this study, PCA, run theory, the MK test, and KORE and EEMD methods were used to systematically explore the spatiotemporal characteristics of drought in the Nanpan River Basin in Yunnan, China, based on the SPI6 series of 33 stations over 61 years. The results indicated that: (1)The Nanpan River Basin to be divided into three homogeneous regions (northern, southwestern and southeastern areas). The drought duration varied among the three subregions and was the shortest (5.30 months) in the southwestern region and the longest (6.25 months) in the southeastern region. The drought magnitude was similar in the different subregions (approximately − 4.0).(2)The long-term drought variation trend showed that the Nanpan River Basin became drier over the studied period. The variation trends of drought duration and drought magnitude in the same subregion were similar. In the southeastern region, the drought duration significantly increased whereas the drought magnitude apparently decreased. There were no obvious trends in the drought duration and magnitude in the northern and southwestern regions.(3)Over the 61 years, the drought yearly occurrence rate showed an overall upward trend, indicating that the frequency of drought events with a moderate drought and above in the Nanpan River Basin increased, even though the drought yearly occurrence rate in the three homogeneous regions fluctuated in different periods.(4)The drought cycles in the Nanpan River Basin were mainly less than 10a, and the quasi-cycles in the three subregions were all 3a; these results passed the significance test at the 80% confidence level. On a period scale of more than 10a, only the southwestern region showed quasi-15a and quasi-31a cycles, which passed the significance test at the 95% and 90% confidence levels, respectively.