Research On Water Level Variation Characteristic In Different Regions Of Poyang Lake

Poyang Lake is the largest open fresh water lake in China.The water level is affected by the geographical location and the water from the Yangtze River and the "Five Rivers",and the water level changes in different regions are complex.Therefore,based on the daily water level data of six water level stations in the Poyang Lake region from 1964 to 2012,this paper analyzes the data at different time scales,and uses mathematical statistical methods to different regions of Poyang Lake.The characteristics of water level change in different time scales are studied.The main results are as follows:(1)Based on the analysis of the annual characteristic water level in different regions of Poyang Lake from 1964 to 2012 by using the sliding average method and the linear tendency method,the change trend of the annual characteristic water level in different regions is obtained as follows: the annual average water level and the annual maximum water level are generally in a downward trend,and the annual minimum water level is in a downward trend except for Hukou and Xingzi station.By means of Mann Kendall mutation test and sliding t test,it is found that the annual average water level in different regions of Poyang Lake has experienced a mutation from high to low in 2004;the year of annual maximum average water level mutation has experienced a mutation from high to low in 2004;the year of annual minimum water level mutation in Hukou station is 2005,Xingzi station is 2004,Duchang station is 2007,Wu Station City station was in 2008,Tangyin station and Kangshan station were in 2003.Through the analysis of the resonance period between each two regions by wavelet cross transform,it is found that the annual average water level in different regions of Poyang Lake has a main resonance period of 6-10 years;the highest water level in different years has a main resonance period of 6-8 years;the lowest water level in different regions has a main resonance period of 6-9 years.(2)Using mathematical statistics method to analyze the water level data of different regions of Poyang Lake in flood and non flood seasons,it is found that the water level of Poyang Lake increases successively from north to south,and the two stations with the largest increase are Xingzi Hukou station.There are 5-7 months main resonance period between different regions.In non flood season,Poyang Lake experienced the process of "rise drop rise" of water level from north to south.And there are 5-7 months main resonance period between different regions.(3)Using mathematical statistics method to analyze the water level data of Poyang Lake in four seasons,and analyze the trend change,mutation and periodic change of water level in different regions of Poyang Lake in four seasons.It is found that the water level of Poyang Lake in four seasons shows a downward trend from 1964 to 2012,with the largest downward trend in autumn and the smallest downward trend in winter.The years of water level mutation of Poyang Lake in four seasons are 2003,1999 and 2002,2005,which have experienced from high to low.There is a main period of 25-30 years between 1964 and 2012.In spring,Hukou Wucheng and Hukou Tangyin have 1-3 and 7-10 year main resonance periods;in summer,Hukou Wucheng and Hukou Tangyin have 2-5 and 7-9 year main resonance periods;in autumn,Hukou Wucheng and Hukou Tangyin have 5-8 year main resonance periods;in winter,Hukou Wucheng and Hukou Tangyin have 1-5 and 7-9 year main resonance periods.(4)Analyze the annual and interannual change trend of the average water level in different regions of Poyang Lake.The result of the analysis of the annual change trend is: the highest water level in July,the lowest water level in January;the result of the analysis of the interannual change trend is: the interannual change trend of the average water level in different regions of Poyang Lake shows a downward trend,among which the decline of Duchang station is the largest and that of Tangyin station is the smallest.The change trend is the same as the annual average water level.The interannual variation trend of monthly water level in different regions of Poyang Lake from January to December is as follows: the water level in March and August shows an upward trend from 1964 to 2012,and the water level in October and November shows a downward trend from 1964 to 2012.