Caractérisation de la mémoire des bassins versants par approche croisée entre piézométrie et séparation d'hydrogramme

Abstract

Intensity and duration of low-flow events depend not only on climatic conditions during the current hydrological year. Wetness or dryness of past years may have an influence on observed flow during droughts, especially in catchments where low-flows depend on aquifers. Understanding this multiyear memory phenomenon is key to explain drought dynamics. Two approaches are considered to evaluate this memory effect. First, the multiyear dynamics of piezometers are compared to yearly climatic fluctuations, in catchments where low-flows are known to be dependent on aquifer storage. Second, hydrographs are decomposed into a slow component, called baseflow, and a quick component, called quickflow. Multiyear fluctuations of baseflow are a conceptual descriptor of observed low-flow dynamics. In this article, we apply a conceptual hydrograph separation method to four catchments in the Huisne basin and we analyse the memory of seven piezometric time series through a linear regression. These piezometers represent the dynamics of three major aquifers in the basin. Results show a correlation between streamflow and piezometer memory. In particular, the long memory of the Perche sands aquifer is highlighted.