摘要
•New, efficient conservative TVD finite volume scheme for scalar transport.•Fully asynchronous time-accurate local time stepping.•Element-local CFL stability condition.•Small elements do no longer restrict the time step of large elements.•CPU time reduction of up to one order of magnitude for water quality simulations.•Coupling of the scalar transport model with a semi-implicit model for hydrodynamics.•Well suited for the study of river–lake systems or river–ocean interfaces.