Salt

The unit models the transport of salt in an estuary or other channel.

Description

Salinity is of most importance in estuaries. A longitudinal variation of salinity and hence density will affect the flow regime. In addition, the amount of oxygen that can be dissolved in salt water is significantly less than that in fresh water. Salinity variations are therefore important when predicting oxygen balance in estuaries.

In some applications, the prediction of salinity distribution may be the main purpose of the study. The prediction of salt water contamination at an intake site would be an example. In most water quality modelling exercises in estuaries salinity is used as a longitudinal dispersion tracer. Salt is a conservative substance so its variation in time and space will be solely due to its advection and dispersion by the flow. Salt transport can therefore be used to determine the values of the empirical longitudinal dispersion coefficients (see DIFFUSION).

Salt may be simulated in one of two ways. It can be set as a constant background value, which may be appropriate in a coastal situation. In this case the keyword 'CONSTANT' should be used. Salt can also be modelled as a conservative pollutant which is transported and dispersed by the flow in which case the keyword VARIABLE should be used. Salt concentrations should then be set as boundary conditions and in the initial conditions.

General

The SALT module may be run independently of the other water quality modules. If a water quality module such as DISSOLVED OXYGEN is simulated then the SALT module is switched on automatically. If a salt concentration is not specified, salt is simulated at a constant value of 0ppt (ie fresh water). The salt module simulates the transport of the variable name:

• Salt (ppt)

This variable is a transported variable when the keyword, VARIABLE, is used.

Overview

Summary Descriptions

Related Topics

Water Quality Processes

See Also

Salt Data Fields