Influence of transient storage on solute transport and the parameter sensitivity analysis in a suburban drainage ditch

From September to October 2013, five in-stream tracer experiments involving slug additions of chloride were performed in Guanzhenhe Branch, a headwater stream in suburban Hefei. From the perspective of different transport mechanisms such as transient storage, lateral inflow and advection-dispersion, four scenarios were set to analyze the effects of transient storage on solute transport in the drainage ditch. And sensitivity analysis of parameters in OTIS model was conducted. The results showed that transient storage exerted a significant influence on the peak values of simulated chloride concentration breakthrough curves (BTCs) in the main channel, and the REs (relative errors) of peak values in the BTCs ranged from 24.23% to 117.26%, which were much higher than those of the peak times. Meanwhile, the effects on simulated BTCs of transient storage markedly exceeded those of lateral inflow. Correlation analysis results showed that A(s)/A were significantly correlated with the peak value REs and the peak time RE's, respectively. Moreover, the ranking of parameter sensitivity in OTIS model was A > A(s) > α > D.