Abstract: To understand the characteristics of variations in precipitation, drought and flood over a karst basin in Southwest China are examined on the basis of the 1979-2019 data series of monthly precipitation at 12 ground stations in the Chengbi River basin, using methods of the Sen’s slope estimation, wavelet cycle analysis, empirical orthogonal function (EOF) analysis, and standardized precipitation index (SPI). The results show that in this basin, its annual precipitation presented a nonsignificant increasing trend over 41 years with the main period of 30 a; its precipitation was concentrated in summer showing nonsignificant changes; and an overall pattern of increase from southeast to northwest. EOF analysis reveals three precipitation patterns in the basin: consistent variation across the basin that is dominant, and the other two showing opposite trends. In the basin, a change from drought events to flood events occurred in 1994, resulting in its frequency of floods higher than its frequency of droughts; the spatial distribution characteristics of its drought and flood events changes are somewhat variable. The results are useful to the basin's precaution and preparation against drought and flood events.

Key words: precipitation, drought and flood, empirical orthogonal function analysis, standardized precipitation index, Chengbi River basin