One-Dimensional Particle Tracking with Streamline Preserving Junctions for Flows in Channel Networks

Abstract

A pseudo-three-dimensional particle tracking model of drifter paths has been developed to study the movement of scalars through a complex network of tidal channels and junctions. To better simulate dispersion caused by bifurcation and merging at junctions, a localized model is proposed in which particles move along potential flow streamlines through junctions. The model is applied to the Sacramento–San Joaquin Delta in the California Central Valley, and the approach reproduces the observed ultimate fate of the endangered native fish Delta smelt more accurately than a model that fully randomizes particle positions at junctions. The new model also reproduces the very large dispersion that has been previously inferred from Delta-wide heat balances; this large dispersion appears to be associated with flow splits at junctions. Overall, the streamline-following model is likely to be more accurate for long-term planning and management simulations of such complex estuaries than more commonly used cross-sectionally averaged Lagrangian transport equation solvers, which randomize concentration distributions of scalars at junctions, and thereby do not reproduce the increased dispersion mechanisms.