Turbidity Calculations to Assess Impacts on Water Quality

Non retained eroded soil eventually reaches water bodies, after being collected as suspended solids by small waterways and/or stormwater systems. The discharge from a collector into a water body leads to the dilution of the solid load, i.e., the progressive decrease of the suspended solids concentration, constituting a so called turbidity plume. Likewise, dredging operations produce a local increase of concentration of suspended solids in the water body which, under the action of water currents, also leads to a turbidity plume.
Turbidity plumes can negatively impact on water uses in neighboring areas. Then, predicting the expected turbidity plume constitutes a requirement to impose restrictions on the source of pollution or on the impacted areas. Depending on the potential consequences of the impacts and/or the stage of the assessment process, calculation methods range from simple analytical models, to elaborated numerical models.
In this presentation, an overview of available methodologies for turbidity plume calculation is offered, with their scope and limitations, illustrated through applications to specific field problems in fluvial, estuarine and maritime environments. As the theoretical model for turbidity plumes is essentially the same that for pollution plumes, some pollution problems are also used for illustration of the methodology.
More specifically, the following problems (all located in Argentina) are described:
• Treated sewage water discharge towards the Barranqueras River, using an analytical model for the first assessment and a numerical model for the final assessment.
• Heated water discharge from a liquefaction vessel towards an estuarine environment (analytical).
• Treated industrial water discharge towards a river through an outfall (numerical).
• Dredging operations along a river (parametric).
• Heated water discharge towards a river (numerical)
• Turbidity due to landfill operations in a coastal zone (numerical).
• Treated sewage water discharge towards a maritime environment through an outfall (numerical)