Characteristics of flood and drought events of the last half millennium in Huaihe River basin

This study identifies characteristics of flood and drought occurrence of the last half millennium and their evolution to the past years in the Huaihe River basin based on various sources of data recording historical flood and drought events and disasters, including observed rainfall data, reconstructed wet season rainfall data, historical flood/drought index, history documentary record of floods and droughts, and history flood survey. The reconstructed wet season rainfall and historical flood/drought index are primarily applied to investigate spatial and temporal characteristics of flood/drought events of the last half millennium using the methods of smoothing average, frequency analysis, wavelet analysis and Mann-Kendall tests. Results indicate that over the past half millennium period, flood and drought events were most severe in the 17th century, but occurrence of extreme flood/drought events was most frequent in the 20th century. It is found there was a relatively stable periodic variation of about 40 years over the past half millennium, and the periodic term had been shortened, from 15-20 years before the 18th century to 5 years in the 19th century, and even 2-3 years in recent 20 years. This increasing tendency indicates that the floods and droughts would severely threaten the economic and social development in the study basin.