Preliminary investigation of seasonality in the Great Berg Estuary

Abstract

The hydrodynamics and water quality of the Great Berg Estuary were studied under river flow conditions typical of the winter and summer seasons. Results reflect a strongly seasonal regime with the estuary exhibiting fluvial dominance during winter and marine dominance under the low-flow conditions of summer. Limited renewal of estuarine water occurs over the summer period with the result that a plug of characteristically estuarine water is formed. Tidal influence extends 69 km upstream of the mouth in summer, while salinities in excess of 5 x 10(-3) occur 37 km from the mouth. The role of river flow in counterbalancing the upstream dispersion of salt during the summer season is highlighted. The relevance of these findings in the preliminary assessment of the freshwater requirements of the Great Berg Estuary is addressed.