Abstract: In this study, we chose ten major river basins in China as the study area, and defined southern and northern river-basin regions. The northern region includes the Songhua River, Liaohe River, Haihe River, Yellow River and Northwest China rivers, and the southern region contains the Huaihe River, Yangtze River, Pearl River, Southeast China rivers and Southwest China rivers. Variation characteristics of the nationwide-averaged maximum daily rainfall amount and heavy rain (daily rainfall amount≥50.0 mm) frequency over each river basin and the northern and southern regions were analyzed by using the daily precipitation data over China for the last 53 years of 1956-2008. Results indicate that maximum daily rainfall amount averaged over the entire country showed no obvious trend, but there were some differences between southern and northern river basins, with increasing trends over southern river basins but decreasing trends over northern river basins especially after 2001. The frequency of heavy rain displayed an indistinct increasing trend over the whole China, but exhibited an increasing trend in the southern river basins and a decreasing trend in the northern river basins. On the whole, more heavy rain occurred in the 1990s than in other decades, with the least heavy rain in the 1970s.

Key words: river basin, heavy rain days, extreme precipitation, climate change, China