An improved equation development for longitudinal dispersion coefficient

The model developed in this paper is an improved equation for the longitudinal dispersion coefficient, which is an important parameter used to monitor and check the assimilatory capacity of rivers. This research incorporates total suspended solids (S-s) and total dissolved solids (D-s) to others selected functional parameters in order to investigate the contributions of S-s and D-s on the longitudinal dispersion coefficient. A new equation is derived for the Orashi River and rivers of the same hydraulic characteristics. The results from research indicate that the presence of S-s and D-s affects the longitudinal dispersion coefficient as it reduces the magnitude of D. The measured values of longitudinal dispersion coefficient estimated in this study vary between 71 and 104.4 m(2) s(-1). The percentage of D-r values estimated to be within 0.0 and 0.3 were 50.0% and within -0.3 and 0.0 were 50% for the developed equation and this indicates a degree of accuracy of 100.0%. While for Seo and Cheong (1998), the percentage of D-r values determined to be within 0.0 and 0.3 were 63.3% and within -0.3 and 0.0 were 30% and records a degree of accuracy of 93.3% and others are poor. SE, NME and MME results show a high accuracy for the derived equation revealing the adequacy of the derived equation in the estimation of D.