Characteristics of multi-scale drought and flood in the Pearl River basin from 1960 to 2019

Drought and flood disasters in the Pearl River Basin have great impacts on the ecological environment and social economy. It is of great significance to understand the spatiotemporal evolution characteristics of drought and flood disasters in order to formulate corresponding strategies in time. The ANUSPLIN meteorological interpolation method, Sen-median trend analysis, Mann-Kendall test, Hurst index and Empirical Orthogonal Function (EOF) methods were used to analyze the spatio-temporal variation of rainfall and multi-scale drought in the Pearl River Basin based on the monthly precipitation data of 43 meteorological stations and standardized precipitation index (SPI) from 1960 to 2019. The results showed that: 1) the average annual rainfall showed an insignificant increasing trend (P>0.05). The spatial distribution pattern of rainfall was high in the northeast and low in the southwest of the study area. 2) The inter-annual SPI showed an insignificant upward trend (P>0.05). The seasonal SPI showed a significant spatial difference, and SPI showed an insignificant change trend in most part of the study area (P>0.05). 3) The area that Hurst index changing continuously accounted for 90.98%, and the β-Z-H coupling results indicated that regions with significant reduction and strong persistence were belonged to the key monitoring areas of drought and flood disasters. 4) The cumulative variance of first 3 eigenvectors of EOF analysis contributed to 58.02%, the first modal reflected the whole river basin had consistent characteristics. The second and third modals reflected the west to east and the north to south reverse distribution respectively. The temporal trend of three modal had an insignificant change trend (P>0.05), and there were no significant mutation points. In conclusion, the spatiotemporal evolution of multi-scale drought and flood in the Pearl River Basin was revealed, and the spatiotemporal modal characteristics of drought and flood were clarified. The results can provide a scientific basis for drought warning in this region.