Surface Water : riv
Surface Water is one component of the FRAMES system. Of the many types of surface water bodies (e.g., nontidal rivers, estuaries, lakes, open coasts, reservoirs, impoundments, etc.) in which constituent fate and transport could be simulated, only a nontidal river model is currently incorporated. Nontidal rivers refer to freshwater bodies with unidirectional flow in definable channels. Other surface water models can be added when deemed necessary.
The surface water component provides estimates of constituent concentrations in a river at locations downstream from a release point. The computed constituent concentrations are used by the exposure assessment component of FRAMES to calculate dose and the resulting health effects to the surrounding population. Potential exposure of humans to constituents via rivers can be associated with ingestion (e.g., drinking contaminated water), inhalation of volatile pollutants (e.g., showering), dermal contact to chemicals (e.g., swimming), or external dose from radionuclides (e.g., swimming).
Because annual-average constituent releases to a river are relatively long term compared to typical constituent travel times in a river, the migration and fate of constituents through the riverine pathway are described by the steady-state, two-dimensional advective-dispersive equation for solute transport. The results are based on an analytical solution that is well established in the scientific literature. The surface water equation accounts for the major mechanisms of constituent persistence (i.e., degradation/decay), advection, and hydrodynamic dispersion. Persistence is described by a first-order degradation/decay coefficient. Radionuclide decay products are also accounted for. Advection is described by constant unidirectional flow in the longitudinal direction. Hydrodynamic dispersion is accounted for in the lateral direction. The processes associated with adsorption/desorption between the water column and suspended and bed sediments are not addressed. Neglecting these processes should, in most cases, represent a conservative assumption with regard to water column constituent concentrations.
Contamination can enter the riverine environment in one of three ways. The ground water pathway can supply transient constituent fluxes along the stream bank adjacent to the aquifer. Overland runoff can supply nonpoint-source constituent fluxes from the land adjacent to the stream. Finally, the surface water component of FRAMES allows direct discharges to the stream.
TYPICALLY CONSUMES . . .
TYPICALLY PRODUCES . . .