Abstract: Monthly precipitation data of 42 rain stations over the Pearl River basin for the period 1960-2005 were analyzed to classify anomalously dry conditions using the 6-month standardized precipitation index. Trends of the SPI-based droughts were detected using Mann-Kendall technique. The results are shown as follows. (1) The western part of the Pearl River basin tends to be dryer and the eastern part tends to be wetter. Enhancing droughts are observed mainly in November, December, and January, and increasing wetting tendency in January and July. Meanwhile drought duration and severity show insignificant trends. (2) The drought risk across the Pearl River basin is very high and the highest drought risk is found mainly in the eastern part of the basin. Besides, the results also show that long-lasting droughts are highly probably the severe droughts. Moreover, the drought risk is greatly increased in the eastern Pearl River basin, when droughts of higher severity occur in the Pearl River basin. These results may imply tremendous challenges for the water resources management in the Pearl River basin, particularly the eastern part of the Pearl River basin. The second return period represents many situations of drought, so the result of the second return period may be more robust.

Key words: drought, drought risk, copula functions, the secondary return period, Pearl River