Lagrangian Transport Modeling with Qual II Kinetics

A one‐dimensional Lagrangian transport model that alleviates the numerical difficulties associated with the use of an Eulerian reference frame by simulating convection with a parcel‐tracking algorithm is presented. The Lagrangian transport model (LTM) also simulates dispersion and tributary (or point) and nonpoint inflows and withdrawals. Convection and dispersion of dye in a laboratory flume with unsteady flow is accurately simulated by the LTM. Up to 10 water quality constituents can be simulated with reaction kinetics defined by the user in a decay‐coefficient subroutine. The reaction kinetics of QUAL II, a popular, steady‐state, Eulerian, water quality model, are inserted into this subroutine. The LTM reproduces QUAL II results and shows diurnal and unsteady loading effects in the Chattahoochee River.