洪泛湖泊水位-流量关系的非线性特征分析

湖泊的水位-流量关系是湖泊水文特性的重要表征。该关系与湖盆形态、湖泊与周围水系的水力联系等因素有关。鄱阳湖是长江中游的大型通江湖泊,洪泛特征显著。本文以鄱阳湖为例,研究洪泛湖泊入湖流量-湖泊水位关系及非线性特征。基于1960~2010年实测湖泊日水位和流域日径流数据,采用交叉小波和小波相干方法分析多时间尺度上水位对入湖流量的响应关系。结果表明,鄱阳湖入湖流量-湖泊水位关系存在3个特征阶段:阶段1中,入湖流量与湖泊水位相位差从0°过渡到45°~90°,水位上升初期与流量同步上升,后期水位对流量的响应产生迟滞效应,滞后时间为2~9d;阶段2中,入湖流量与湖泊水位相位差在90°左右波动,入湖流量率先下降,湖泊水位却保持缓慢上升;阶段3中,入湖流量与湖泊水位的相位变化与阶段1相反,从45°~90°过渡到0°,湖泊水位与入湖流量下降逐渐变为同步。本文提出鄱阳湖入湖流量-湖泊水位关系的3个阶段并分析其产生的主要原因,概化其水文特征,对通江洪泛湖泊的水文特征有新的认识,为下一步湖泊水文过程的刻画与模拟提供重要理论基础。

ANALYSIS ON NONLINEAR HYDROLOGIC CHARACTERISTICS OF STAGE-INFLOW RELATIONSHIP IN POYANG LAKE

Stage-inflow relationship,which is affected by bathymetry of the lake,hydrodynamic connection between lake and surrounding rivers,is an important hydrological characteristic of a lake.Poyang Lake,located in the middle Yangtze River,presents significant floodplain features.This paper aims to explore the lake stage-catchment inflow relationship and the nonlinear characteristics of Poyang Lake.Cross wavelet transform (XWT) and wavelet transform coherence (WTC) were used to analyze the corresponding relationship between stage and inflow based on measured data of daily stage and catchment inflow during the period of 1960-2010.The stage-inflow relationship showed apparently three phases.In the first period,the phase difference between stage and inflow changed from 45 to 90 degree.A delay time of 2-9 days was detected between the two variables.In the second period,the phase difference was about 90 degree.The inflow decreased firstly while the stage remained increasing.The change of phase difference in the third period was almost the reverse of the first,which changed from 90 degree to zero.This paper conceptualized the lake stage-inflow relationship to three phases,which provides a new understanding of the hydrological characteristics of the lake-floodplain system.The results provide an important theoretical basis for describing and simulating the hydrologic processes of Poyang Lake and other similar lakes.