10.4122/1.1000000718
Zhang, Fan
Fan
Zhang
zhangf@ornl.gov
Yeh, Gour-Tsyh
Gour-Tsyh
Yeh
gyeh@mail.ucf.edu
Zhang, Fan
Fan
Zhang
zhangf@ornl.gov
An Integrated Media, Integrated Processes Watershed Model – WASH123D: Part 7 – Sediment and Reactive Chemical Transport in Surface Runoff
XVI International Conference on Computational Methods in Water Resources
2006
2006
A watershed system includes river/stream networks, overland regime, and subsurface
media. This paper presents a numerical model of sediment and reactive chemical
transport in surface runoff of watershed systems. The distribution of mobile
suspended sediments and immobile bed sediments is controlled through hydrological
transport as well as erosion and deposition processes. Transport of chemical
species with a variety of chemical and physical processes is mathematically
described by system of M advective-dispersive-reactive transport equations (where M
is the number of species). Decomposition via Gauss-Jordan column reduction of the
reaction network transforms M species-transport equations into three sets of
equations: a set of thermodynamic equilibrium equations representing NE equilibrium
reactions, a set of reactive transport equations of NKI kinetic-variables involving
no equilibrium reactions (where NKI is the number of linearly independent kinetic
reactions), and a sent of NC component transport equations (where NC is the number
of components). The elimination of fast reactions from reactive transport equations
allows robust and efficient numerical integration. The model solves the PDEs of
kinetic-variables and components rather than individual chemical species, which
reduces the number of reactive transport equations and simplifies the reaction
terms in the equations. A hypothetical example was used to demonstrate the
capability of the model in simulating sediment and reactive chemical transport
subject to a complex reaction network involving both slow and fast reactions, under
the effect of temperature. Based on the application of an eutrophication example,
the deficiency of current practices in the water quality modeling is discussed and
potential improvements over current practices using this model are addressed.