One year of Suspended Particle Matter (SPM) and carbon fluxes on an Alpine river: l'Isère

Abstract : This study describes Suspended Particle Matter (SPM) and Carbon fluxes on an alpine river (l'Isère), uspstream from Grenoble (5 570 km2). SPM concentrations are measured with a turbidity probe and data are collected every 30 minutes. It requires calibrating a relation between SPM concentrations and turbidity values. This was done during some events when important SPM transport was observed. The high frequency database permits to highlight SPM concentrations temporal variability at different scales, from seasonal to sub-daily variability. The data are also used to investigate the influence of sampling frequency on annual fluxes precision. For the Isère river, it is recommended to measure SPM concentrations at least every 12 hours, in order to evaluate annual fluxes with a precision higher than 20 %. Carbon fluxes estimated through a weekly survey and during flood events are 39 t km-2 an-1 mainly exported under inorganic form (80 %) and dissolved form (58 %).