Accurate Modeling of River Pollutant Transport

A simple, accurate, Lagrangian numerical scheme is developed for modeling the advection and dispersion of a nonconservative pollutant in one‐dimensional, nonuniform river flow. The scheme is free from the common propensity to produce false oscillations and smearing in steep front regions. Testing of the scheme demonstrates its high accuracy, which is maintained on very coarse grids. A successful application is demonstrated in which it has been used to model the passage of patches of anoxic water down the Waipa River, New Zealand. Longitudinal dispersion coefficients were inferred by matching model predictions to observed steep fronts of DO and BOD5. These were confirmed by subsequent dye studies. River reaeration and deoxygenation coefficients were also inferred, these being useful for management oriented simulation in this river and elsewhere.