Sediment resuspension due to density currents caused by a temperature difference: application to the Flix reservoir (Spain)

Abstract

Density currents occur in lakes and sea environments when two masses of water interact giving rise to a relative movement between them. Depending on the initial and boundary conditions, turbulence associated with them is able to lift the sediment. This fact can be a problem in places where the sediment is contaminated due to industrial activities. In 2001, a pollution episode occurred in the Flix reservoir (Tarragona, Spain), in which thousands of fish died and the water supply of cities such as Tarragona was affected. This study analyses the possibility of a density current due to a temperature difference as the explanation for this event. The previously developed one-dimensional, Lagrangian model BANG 1D of subaqueous turbid surges has been modified to incorporate temperature evolution. The obtained results show that a temperature difference can generate a density current that is able to resuspend the sediment although the grade of erosion highly depends on the initial velocity of the current.

Keywords:

• Density currents
• mercury
• numerical model
• resuspension
• temperature

Acknowledgements

This work was developed within the framework of the project “Estudi de la dinàmica dels compostos organoclorats persistents i altres contaminants en els sistemes aquatics continentals”. The authors thank GITS research group for its financial and personal help, the Spanish ministry of education for the grant given to the first author for the development of his thesis and the anonymous referees for their constructive criticism, which contributed to the improvement of the paper.