Estimation des incertitudes de mesure sur les débits et les charges polluantes en réseau d'assainissement : application au cas d'un bassin de retenue-décantation en réseau séparatif pluvial

Estimation of uncertainties on discharges and concentrations measurements in a storage and settling tank during rainfall events

Laboratoire URGC Hydrologie Urbaine, INSA de Lyon, 34 avenue des Arts, 69621 Villeurbanne Cedex, France

Auteurs de correspondance : jlbk@urgc-hu.insa-lyon.fr bardin@urgc-hu.insa-lyon.fr

Abstract

It is necessary to assess adequately measurement uncertnainties of experimental data in urban hydrology in order to draw pertinent and valuable conclusions from measurement results. This paper first gives a brief presentation of the concepts relative to standard uncertainties and to the law of propagation of uncertainties. Then it presents an example of calculation of the uncertainties of some variables describing the behaviour of the Vénissieux (France) storage and settling tank during one rainfall event. These variables are the flow rates and the volumes entering into the tank, the inflow and outflow mean concentrations and masses of TSS (Total Suspended Solids), and the TSS removal rate. Variographs are used to account for the autocorrelation of time series data. The results lead to the following relative uncertainties: 8% for the total volume, 30% for the inflow concentration, 38% for the outflow concentration, 31% for the inflow mass, 39% for the outflow mass and 138% for the removal rate.