Signal Analysis of Water Quality Indicators

Abstract

Managing freshwater ecosystems is quite challenging because of the complexity of these systems. Their management requires a good understanding of the components and their interrelationships. Physical, chemical and biological variables are recorded across time and serve as indicators, giving information concerning the state and changes of these systems as well as the stressors and natural driving forces present. In order to extract as much information as possible from the recorded indicators, signal analysis methods such as wavelet analysis are used. In this paper, some results of analysing water quality indicators with signal analysis methods are presented. Wavelet analysis, a modern signal analysis tool is used to investigate the time scale behaviour of an ecological state indicator, dissolved oxygen as well as its relationship with water temperature, a natural driving force, at different time scales. This analysis reveals the long term evolution of the ecological indicator at different resolutions, the dominant scale of variability in the signal and its correlation and cross-correlation with water temperature on a scale by scale basis.