Use of hydrological signatures to characterize the hydrological functioning of catchments from the OZCAR French Critical Zone

International audienceThe French OZCAR Critical Zone Observatory network gathers experimental catchments that cover a large range of climate, geology, vegetation and land uses. This network offers the opportunity to characterize and compare the hydrological functioning of a large set of catchments. For this purpose, the hydrological functioning of 30 catchments from the OZCAR network was characterized using a set of hydrological signatures proposed by Horner (2020). These hydrological signatures were designed to characterize the hydrological regime and the main components of the hydrological cycle and computed using long-term daily rainfall and discharge time series. Statistical analyzes (Principal Component Analysis -PCA, Hierarchical Clustering on Principal Components -HPCP) were carried out to identify similarities / dissimilarities in the behavior of the catchments according to their hydrological signatures and their geology, climate, land use, and topography. The following questions were addressed: 1/ Is the set of hydrological signatures relevant to characterize the functioning of catchments and to identify classes of similar hydrological behavior? 2/ Can the obtained classifications be explained by the hydro-climatic and physiographic characteristics of the catchments? A first analysis was conducted using only data from catchments located in Metropolitan France, and a second analysis included all the catchments, noticeably tropical catchments subjects to monsoon climate. From the set of hydrological signatures of catchments located in Metropolitan France, classes were identified according to their slow or fast flow generation processes, their storage capacity and water release characteristics. Groups of catchments marked by high proportions of base flow, high groundwater contributions, intermittency of flows, high runoff or seepage, rapid or slow recession, small or large water storage were distinguished. When climatic and physiographic characteristics of the catchments were included in the analysis, new classes emerged, with factors such as geology, land use, slope, elevation, drainage density, topographic moisture index strongly influencing the classification. When all the catchments, including tropical ones were considered, differences in climate characteristics were found to dominate the catchment classification