Hybrid-Cells-in-Series Model for Solute Transport in a River

A hybrid-cells-in-series (HCIS) model has been conceptualized to simulate transport of a conservative solute in a river. The concentration graph of the effluent from the first hybrid unit follows a skewed concentration-time profile more close to reality. When the linear size $\Delta x$ of the hybrid unit is more than $4D_L/u$, where $D_L=$longitudinal dispersion coefficient, $u=$ mean flow velocity, the concentration graphs at $n\Delta x$, $n=1\text{,}2\text{,}3\text{,}\dots$ are approximately equal to that predicted by Ogata and Banks’ model. The model parameters $\alpha$, $T_1$, and $T_2$, which are the times of residence of solute in the plug flow zone, and in the first and second thoroughly mixed reservoir respectively, can be estimated from a time-concentration graph using: (1) partial moments, (2) three characteristics of the graph, i.e., time to peak, peak concentration and the partial first moment, and (3) least square optimization. The performance of the HCIS model has been verified using the data of field tests conducted in rivers. The model parameters estimated using one concentration graph simulate the concentration graphs observed at other location downstream with reasonable accuracy.