Prediction of the longitudinal dispersion coefficient for small watercourses

Longitudinal dispersion coefficient (DL) is considered an essential physical parameter to water quality modeling in rivers. Therefore, the estimation of this parameter with high accuracy guarantees the reliability of the results of a water quality model. In this study, the observed values of longitudinal dispersion coefficient are determined for natural streams (with discharge less than 2.84 m(3)s(-1)), based on sets of measured data from stimulus-response tests using sodium chloride as a tracer. Additionally, a semiempirical equation for prediction of D-L is derived using dimensional analysis and multiple linear regression technique. The performance of the produced equation was compared to five empirical prediction equations of D-L selected from literature. It presented correlation coefficient r(2) = 0.87, suggesting that this equation is suitable for the estimation of D-L in streams. It also presented better results for predicting the DL than the five equations from literature, showing an accuracy of 71%.