Investigating transport properties and turbidity dynamics of a karst aquifer using correlation, spectral, and wavelet analyses
Investigating transport properties and turbidity dynamics of a karst aquifer using correlation, spectral, and wavelet analyses
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DOI：
10.1016/j.jhydrol.2006.02.021
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发表时间：
2006-09-30
影响因子：
6.4
通讯作者：
Ogier, S.
中科院分区：
文献类型：
--
作者：
Massei, N.;Dupont, J. P.;Ogier, S.
在世界上许多地方，饮用水经常受到浑浊的污染。然而，这种浊度作为颗粒传输的代表，可以用来追踪颗粒传输特性的某些特征。为了研究岩溶系统中颗粒和溶解物质的运移与水动力之间的关系，对法国塞纳河下游白垩层岩溶泉水系统的降雨量时间序列(输入信号)、水位、比电导和浊度(输出信号)进行了相关和频谱分析。这个系统由一个弹簧连接到白垩岩高原上的一个天坑上，那里有一条小溪进入地下。水位和浊度的自相关函数表现出较短的记忆效应，说明洪水事件对这两个参数的影响持续时间较短，而比电导(代表矿化程度较低的风暴水)具有较长的记忆效应。这些结果被解释为反映了泉水对降雨事件的快速反应，裂缝白垩岩中的水储存解释了特定电导率比颗粒更长的记忆效应。通过自相关函数的快速傅立叶变换计算的能量谱在输出信号中显示出很强的结构，而输入信号(降雨)是随机的，因此可以评估和比较关于溶解和固体传输以及水力的系统行为。互相关函数(允许评估脉冲响应函数)证实了系统对于水位和浊度的低惯性以及对于特定电导的高得多的惯性。除了主峰外，互相关函数中的两个次峰还表明存在额外的流动路径，可能涉及其他点源补给和/或通过粘土质表层地层和溶解管道的延迟入渗，这可能起到表层岩溶的作用。使用连续小波谱分析可以更好地研究降雨信号结构，并突出了浑浊度与降雨量之间的强烈关系，这是从能量谱中无法推断的。对水位中的特定光谱成分进行了分离，并利用小波逆变换进行了时间域重建，从而实现了快流和慢流成分的分离：(C)2006爱思唯尔B.V.保留所有权利。
In many places throughout the world, drinking water is frequently contaminated by turbidity. Such turbidity, however, as representative of particle transport, can be used as to trace certain features of particle transport properties. In order to investigate the relation between particle and dissolved species transport and hydrodynamics in karst systems, correlation and spectral analyses were performed on time series of rainfall (input signal), and water level, specific conductance, and turbidity (output signals) at a karst spring system in the chalk aquifer of the lower Seine valley, France. This system is composed of a spring connected to a sinkhole on the chalk plateau where a small creek enters the subsurface. The autocorrelation functions for water level and turbidity showed a short memory effect, demonstrating the short duration of the influence of flood events on these two parameters, whereas specific conductance (representing less-mineralized storm-derived water) had a much longer memory effect. These results were interpreted as reflecting the rapid reactivity of the spring to rain events, with storage of water in the fissured chalk explaining the longer memory effect for specific conductance than for particles. Energy spectra computed by fast Fourier transform of autocorrelation functions showed a strong structure in the output signals, whereas the input signal (rainfall) was random, thus allowing assessment and comparison of system behaviour regarding dissolved and solid transport, as well as hydraulics. Cross-correlation functions (which allow an assessment of impulse response functions) confirmed the low inertia of the system for water level and turbidity and the much higher inertia for specific conductance. In addition to the main peak, two secondary peaks in the cross-correlation functions suggest the existence of additional flowpaths that might involve the contribution of other point-source recharge and/or delayed infiltration through the clayey surficial formation and solution pipes, which could act as epikarst. Analysis using continuous wavelet spectra allowed a better investigation of the rainfall signal structure and highlighted a strong relationship between turbidity and rainfall, which could not be deduced from the energy spectra. Specific spectral components in water level were isolated and a time-domain reconstruction using inverse wavelet transform allowed separation of quick-flour and slow-flow components:. (c) 2006 Elsevier B.V. All rights reserved.