Early outcomes mostly based on historical documents and some few analysis about floods and drought with roughly statistical. Here is the analysis about the changing of flood and drought disasters in Songhua River and Liao River in Northeast.
The changing trend of flood and drought disasters of Songhua River basin was quite the same with Liao River. There were some lows about the occurrence of floods and droughts: in the past 100 years, four obviously changing happened with a cycle of 20 to 30 years, except in 1920s, the difference between north and south was pretty outstand, the rest all met the regulations. The changing of flood and drought disasters in the whole area acted almost the same with Songhuajiang River, whose area takes up about 44.4% of the whole area, and that was make sense.
The flood and drought degree differences between Songhua River basin and Liao River basin as well as the annual runoff changing tendency in Haerbin station, that there was almost a same trend in flood and drought change and rainfall change coupled with the annual runoff changing tendency of Haerbin station. That also demonstrates the rainy periods were flood seasons, corresponding relations were strengthened in recent forty years with more detailed statistics.
The drought and flood period, rainfall as well as annual runoff level of these two basins, we are able to recognize the cycle of 20 to 30 years for flood and drought, rainfall merge with annual runoff, which met the year record too.
The four times periodic changes of flood and drought in the two basins situated in Northeast area in the recent one hundred years with a quasi-periodic of 20 to 30 years. There were flood years in the beginning of this century: 1910s,1930s,1950s,1980s, especially 1909, 1914 and 1917 in 1910s, 1930 and 1932 as well as 1935 in 1930s, 1951 and 1953 and 1957 in 1950s, 1960, 1985 in 1980s. There were drought years in 1920s,1940s, and 1970s, 1899, 1902,1919, 1920 and 1925 and 1926 in 1920s, 1940, 1946,1972 and 1978 plus 1979 of 1970s in particular. There were some odd years during the general regulations, such as the 1923’s flood in drought 1920s, 1982 and 1989’s extreme drought in rainy 1980s, but the general direction is consistent.
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