The evolution analysis of flood and drought in Huai River Basin of China based on monthly precipitation characteristics

Based on the daily precipitation data of 38 weather stations in the Huai River Basin from 1961 to 2010, this study used SPI index, P-III curve to determine the flood/drought years, under what situations for droughts and floods easily happen, and to analyze the evolution law of flood and drought during inter-annual and intra-annual based on the characteristic of monthly precipitation. The results showed that: (1) annual rainfall of the Huai River Basin presented decreasing trend, maximum rainfall appeared from June to August, and multi-year average precipitation increased gradually from north to south; (2) the variation of monthly precipitation during flood years was more severe than other typical years, and precipitation in drought years showed nearly 50 % decline compared with normal years; (3) high rainfall of flood years was mainly caused by the increase in rainfall in flood season, and the strategy of flood control and drought relief was short-term flood prevention and long-term drought relief; (4) while precipitation of most months in drought year was reduced, the relevant strategies annual basin-wide of long-term drought prevention should be carried out; (5) combination events of floods and droughts occurred frequently. Persistent drought dominated in spring and summer while droughts and floods that happened alternately were mainly in summer and autumn.