Scaling behavior of the fluctuations in stream flow at the outlet of karstic watersheds, France
Résumé
This contribution presents a study of discharge variability at two karst springs outlet in southwestern France and aims at presenting the Detrended Fluctuation Analysis (DFA), which method is not very usual in hydrology, to the community interested in investigating the scaling behavior of karst hydrological responses. Several studies have already highlighted the existence of a power law scaling behavior in the spectral variance distribution of hydrological signals such as rainfall rates, stream flow and groundwater levels. This power law behavior provides evidence for characteristic scales that correspond to different physical responses of the system depending on its complexity and occurring at distinct temporal scales. We derive in this contribution particular scaling behavior of karstic watersheds, in particular, the assessment of time interval of karstic watershed responses to rainfall. Based on DFA analysis and relying on a unique high resolution long-term discharge database, we provide evidence for a scaling behavior in the response of two French karstic watersheds. The DFA analysis of discharge time series fluctuations at daily, half hourly and 3-min sampling rate allows to detect scaling behavior in the fluctuation of karstic stream flow from 1 h up to 100-h, from 100-h up to 1-year time scales and for scales larger than 1 year. The DFA analysis can also be useful in investigating groundwater levels or chemical conductance time series scaling behavior and deserves to be more largely disseminated in hydrology as valuable complement to Fourier or wavelet analyses.