Characteristics of drought and flood in Zhejiang Province, East China: Past and future

摘要

On the basis of large amount of historical and measured data, this paper analyzed the regional, periodic, frequency, continuing, and response characteristics of droughts and floods in Zhejiang and proposed the conception of ratio of peak runoff. Main characteristics of droughts and floods in Zhejiang are as follows: 1) The western Zhejiang region is plum rain major control area, and the eastern coastal region of Zhejiang is typhoon major control area. 2) Within a long period in the future, Zhejiang will be in the long period that features droughts. 3) In Zhejiang the 17th century was frequent drought and flood period, the 16th, 19th, and 20th centuries were normal periods, while the 18th century was spasmodic drought and flood period. 4) The severe and medium floods in Zhejiang were all centered around the M-or m-year of the 11-year sunspot activity period. 5) There are biggish years of annual runoff occurred in El Niño year (E) or the following year (E+1) in Zhejiang. The near future evolution trend of droughts and floods in Zhejiang is as follows: 1) Within a relatively long period in the future, Zhejiang Province will be in the long period of mostly drought years. 2) Between 1999 and 2009 this area will feature drought years mainly, while the period of 2010–2020 will feature flood years mostly. 3) Zhejiang has a good response to the sunspot activities, and the years around 2009, 2015, and 2020 must be given due attention, especially around 2020 there might be an extremely severe flood year in Zhejiang. 4) Floods in Zhejiang have good response to El Niño events, in El Niño year or the following year much attention must be paid to. And 5) In the future, the first, second, and third severe typhoon years in Zhejiang will be 2009, 2012, and 2015, respectively.