Measured distribution of water turbidity in Gulf St Vincent

Abstract

Large- and small-scale surveys of the horizontal and vertical distributions of turbidity in the waters of Gulf St Vincent in South Australia have been made under conditions of light winds and smooth to slight seas. The turbidity was characterized by the beam attenuation coefficient at a wavelength of 530 nm, which was determined from measurements made with a transmissometer operated from a boat. The results were evaluated with reference to independent measurements of water density distributions and circulation patterns in the Gulf. The measured values of the beam attenuation coefficient lay between 0.12 and 2.0 m^-1, although most lay between 0.2 and 0.7 m^-1. Both horizontal stratification and vertical uniformity of turbidity were observed and explanations for these two conditions are offered. The relative importance of several influences on water turbidity are assessed; the most important in Gulf St Vincent appear to be the type of bottom sediment, wave action on the sediment, and water currents.