ESTUARIES IN SOUTH AFRICA

Useful links

Main Page	General Information	Catchment Characteristics	Land and Estuary Uses	Ecology
Threats	Hydrodynamics and mouth dynamics	Physical Features	Climate	References
EERSTE RIVER ESTUARY: Water Quality

	Physio-chemical Characteristics
	An assessment in 1981 was as follows (Ref.1.):
	Surface water *temperatures* in the Eerste River estuary varies from 10°C in June to 26°C in December. Surface *salinities* in winter were 0 ppt (parts per thousand) throughout at LWST on the 7^th of June 1982, with the river water running out strongly. At HWST waves flooded over the sandbar and salinities ranged from 22 ppt in the mouth, to 1ppt at the surface, 350m upstream. All this, compared to sea surface salinities measured in the surf, 100m west of the mouth were 25 ppt.
	Dissolved oxygen (DO) concentrations in summer (1 December 1981) ranged from 6.8 ppm (parts per million) to 10.8 ppm in the surface water of the Eerste River estuary, compared to DO values of 4.0 ppm to 8.5 ppm in the bottom waters. In winter the surface DO levels ranged from 8.5 ppm to 10.4 ppm. DO levels in the sewage outfall were 9,4 ppm on the surface and 8.5 ppm at the bottom.
	*Water transparency* measured with a Secchi disk, ranged from 0,75m in the lagoon to 0,3m in the upper reaches of the estuary.
	pH values were measured in the surface waters of the Eerste River estuary and ranged from 8.0 to 8.7 closer to the sewage outfall.
	All of the nutrient values were considerably increased at samples measured from the sewage outfall.
	Pollution
	The Eerste River estuary receives treated sewage effluent directly from the adjacent Macassar sewage works, serving Somerset West and Strand. It also receives sewage effluents indirectly from the Zandvliet sewage works (near the head of the esturay) and from various sewage works upstream on the Eerste and Kuils Rivers respectively.
	Effluents from various industries, including wineries are also discharged in the Kuils River and Eerste River.
	Studies on the pollution of the Eerste and Kuils Rivers indicated that pollutants such as oil, fats, soaps and nutrients were present (Ref. 4). It is also expected that pesticides and herbicides, usually present in water draining from agricultural areas, are polluting the Eerste River water.