Improved implicit numerical scheme for one-dimensional open channel flow equations

Implicit numerical approach proved to be very suitable for solving open channel flow equations especially on large scale domains because of its ability to employ larger time steps and therefore considerably reduce overall computing time. Numerical modelling of open channel flow equations simulating real problems involving irregular channels with variable width introduces the flux space dependency problem that has not been resolved so far in implicit numerical approach. Original finite difference Linearized Conservative Scheme is presented and modifications of flux and source terms are introduced. Numerical flux formulation needed modification in order to account for the spatially variable flux dependency, and consequently the source term is appropriately decomposed. Previous papers analyzed numerically balanced approximations of flux and source terms exclusively in explicit numerical schemes solving open channel flow equations. This paper introduces modifications of numerical approximations of flux and source term thus enabling the use of implicit numerical schemes in open channel flow problems simulations involving channels with nonprismatic geometry. Achieved improvements are presented through several test problems.