Velocity and depth distributions in stream reaches: testing European models in Ecuador

We tested how European statistical hydraulic models developed in France and Germany predicted the frequency distributions of water depth and point-velocity measured in 14 reaches in Ecuador during 25 surveys. We first fitted the observed frequency distributions to parametric functions defined in Europe and predicted the parameters from the average characteristics of reaches (e.g. discharge rate, mean depth and width) using European regressions. When explaining the frequency of three classes of velocity and three classes of depth among reach surveys, the fitted and predicted distributions had a low absolute bias (< 3%). The residual variance of fits relative to the mean class variance was < 18%. The residual variance of predicted frequencies was 30-61% for velocity classes and 20-36% for depth classes. Overall, the European models appeared appropriate for Ecuadorian stream reaches but could be improved. Our study demonstrates the transferability of statistical hydraulic models between widely-separated geographic regions