Comparative analysis of tracer studies in the determination of longitudinal dispersion coefficient

Abstract

The research presented in this paper is to determine the best tracer studies that will give acceptable estimates of longitudinal dispersion coefficient for Orashi river using rhodamine WT dye and sodium chloride as water tracer. Estimated results obtained for longitudinal dispersion coefficient for the case of rhodamine WT experiment ranges between 71 and 104.4 m2s−1 while that of sodium chloride experiment ranges between 20.1 and 34.71 m2s−1. These results revealed lower dispersion coefficient using sodium chloride as water tracer (WT) indicating that for larger rivers, sodium chloride should not be used as water tracer. The usage of sodium chloride as water tracer in the estimation of longitudinal dispersion coefficient is recommended in smaller streams as NaCl is relatively conservative. The established equations for both cases of investigation are proving satisfactory upon validation as degree of accuracy of 100.0% was obtained using discrepancy ratio (Dr). Standard error (SE), normal mean error (NME) and mean multiplication error (MME) of the developed equations is better when compared with other existing equations. However, Equation ( 17) is satisfactorily recommended. HIGHLIGHTS The study gives the range of values of longitudinal dispersion coefficient that can be used to assess assimilatory capacity of the river.; The research established best tracer to be used for sizeable rivers as rhodamine WT dye.; The study will guide in water quality parameters monitoring/assessment.; This investigation gives interpretation of influence of total suspended solids and total dissolve solids on the longitudinal dispersion coefficient.;

Keywords

• hydraulic parameters
• longitudinal dispersion coefficient
• rhodamine wt
• sodium chloride
• total dissolved solid
• total suspended solid