This paper deals with the development of a computational model for predicting the salinity variation in a comparatively long and narrow well-mixed tidal reach. The model is hated on the coupled numerical solution of unsteady flow hydrodynamic equations of continuity, momentum and salinity transport using implicit finite difference scheme. The computational scheme selected is the classical double sweep algorithm, for solving a set of simultaneous linear algebraic equations. The scheme is unconditionally stable and can be used for non-uniform space and time steps. It has also a higher order of accuracy than the existing schemes.
The software developed has been run with the available water level data in the Hooghly River system with appropriate initial and boundary conditions (Reddy et al., 1992). It is then adopted for production runs to provide information with regard to the variations of tidal levels, discharges and salinities.