Validation of an Uncertainty Propagation Method for Moving‐Boat Acoustic Doppler Current Profiler Discharge Measurements

Abstract

AbstractThe moving‐boat Acoustic Doppler Current Profiler (ADCP) gauging method is extensively used to measure the discharge of rivers and canals. Informed decisions related to water management require reliable estimates of the uncertainty of such measurements. The evaluation of the uncertainty is however a difficult task because of the complexity of the ADCP data workflow and the lack of reference discharges in rivers and canals. This study presents an evolution of the OURSIN method, which follows the framework of the Guide to the expression of Uncertainty in Measurement. The method has been implemented in the QRevInt software which provides an ADCP data quality review prior to the uncertainty analysis. As a computationally efficient alternative to the Monte Carlo approach, the uncertainty propagation combines elemental measurement uncertainty sources, transect‐to‐transect discharge variability, and estimation of the uncertainty of discharges in unmeasured areas by sensitivity analysis. The OURSIN uncertainty results are validated using empirical uncertainty estimates from two large‐scale repeated measures experiments with variable site and flow conditions. The mean and the 95% quantiles of the uncertainty differences are −0.4% [−4.4%; +2.5%]. The OURSIN method provides a comprehensive uncertainty budget that is helpful for understanding the relative impacts of error sources and defining strategies to minimize them. The method should be further evaluated with experiments in different conditions, and additional uncertainty components and options such as GPS reference for boat velocity could be implemented.