Assessing the effect of uncertainties in pollutant wash-off dynamics in stormwater source-control systems modeling: consequences of the use an inappropriate error model

International audienceThis study investigates the effect of uncertainties associated with pollutant wash-off dynamics inthe context of stormwater management practices modelling. A formal Bayesian approach is adoptedfor the calibration and the uncertainty analysis of a commonly used wash-off model, under (1) theunverified assumption of homoscedastic, independent and normally distributed residuals and (2)using a more correct heteroscedastic and autoregressive error model. The results obtained for eachof these approaches are compared and the uncertainty associated with water quality modelling islater propagated through a conceptual Best Management Practices (BMP) model, for variousstormwater management scenarios, so as to assess the effect of this uncertainty for BMP modellingand clarify the benefits of a robust description of error structure. This study indicates that theviolation of the statistical asumptions about the residuals may result in unreliable estimation ofmodel parameters and total predictive uncertainty. The effect of the uncertainty in the intra-eventvariability of concentations in runoff is however found to have only a limited effect on the outputsof the BMP model, regadless of the error model adopted for calibration