IVL Swedish Environmental Research Institute

There is often very limited information available about uncertainty in discharge data as it is rarely communicated by data providers. However, ‘soft’ information about station characteristics, climate and flow regime, and catchment characteristics can be used to understand the likelihood that discharge data in a particular location are uncertain. For example, if high flows are of short duration (i.e., a few hours) it is practically quite difficult to manage to gauge high flows, leading to likely extrapolation of stage–discharge rating curves and large high flow uncertainty.

The aim of this commentary is to share – and to encourage sharing – of soft information about data uncertainty sources, to promote more informed decisions on data uncertainty in hydrological studies. We summarize the soft information about discharge data uncertainty as a perceptual model of uncertainty. We find that soft information can inform us about three main types of uncertainty sources: uncertainty related to the hydraulic control, uncertainty related to incomplete gauging of the full flow range, and uncertainty due to measurement error. We believe that a key benefit of the type of generalized perceptual model of uncertainty we present is to facilitate dialogue on, and understanding of, possible sources of observational uncertainties and their impacts.