Constituent modelling concerns the modelling of the concentrations or discharge loads of water quality variables. These might include particulate (e.g. sediment, particulate nutrients) or soluble (e.g. salt, dissolved nutrients) components, or physical characteristics of the water (e.g. temperature, acidity). In BA, constituent modelling is likely to be required only in cases where water quality variables form an integral part of any receptor impact models.
The water quality constituent most likely to be required is salt. Any saltload modelling is likely to take place as a post-processing step (i.e. after landscape and river modelling) using fixed-source concentrations routed conservatively.
Prediction of salt loads in the streamflow requires concentration information for inflows from the groundwater system and the availability of observed load (or concentration) data to validate any mixing assumptions.
