Performance of equations for the longitudinal dispersion coefficient: a case study in the Orashi River

Abstract

Investigation of the water quality of rivers is a key point in Water Resources Engineering. The longitudinal dispersion coefficient is one of the foremost significant parameters in river water quality monitoring. Several parameters such as hydraulic, morphology, total dissolved solids, and total suspended solids are effective parameters in the determination of the longitudinal dispersion coefficient as revealed by this study. The assessment of the river shows mean hydraulic and geometric properties such as flow, depth, velocity, longitudinal slope, and width to be 354.17 m3/s, 9.61 m, 0.69 m/s, 0.0079,101.63 m and the range of the longitudinal dispersion coefficient as (72–104.4) m2/s. Results obtained by employing the established equations revealed standard error indices and RMSE of the developed equation, and Kashefipour and Falconer equation gives correlation coefficient of about 0.819 and 4.182 and 0.421 and 12.186, respectively, as coefficient of determination and RMSE, and they are more accurate among the empirical equations. However, the newly derived equation for the longitudinal dispersion coefficient performed better when compared with others, indicating the fitness of the developed equation to estimate longitudinal dispersion coefficient. HIGHLIGHTS The study provides the choice of equation to be used and to understand the influence of total suspended solids and total dissolved solids on the dispersion coefficient.; The study guides in estimating the assimilatory capacity of a river, that is, the ability of rivers to absorb the pollutants.; The study provides the required guide for the monitoring of water quality parameters.;

Keywords

• longitudinal dispersion coefficient
• rhodamine wt
• rivers
• root mean square error (rmse)
• derived equation