Spatial-temporal variability of the fluctuation of water level in Poyang Lake basin, China

Poyang Lake basin is one of the most biodiversity areas in China. Fluctuation of water level is an important factor of hydrological process which is a guarantee of ecosystem health and biodiversity conservation. To measure its spatial-temporal variation, classical statistical methods and permutation entropy were employed: 1) Variation of water level downstream of Poyang Lake during one year follows a periodical pattern, while it is random in upper reaches. That is, the range of water level in upper reaches is much less than that in downstream. 2) Fluctuation of water level in winter and spring is more complicated, more irregular and more random than that in other seasons. This is because in winter and spring, precipitation directly causes rising in water level rather than generating surface runoff, while it is reversed in summer. 3) The ranges, standard deviation, coefficient of variation and fluctuation of water level decrease with rising in elevation. 4) In sub-basin scale, fluctuation of water level in upper reaches is more complicated than that in downstream, e specially along one river. Mechanically, catchment size and confluence process may be the main factors influencing fluctuation of water level over Poyang Lake basin