The Berg River Estuary

The Berg River estuary is one of the largest of South Africa`s 279 estuaries, with a total area of 61km2.  It is one of the most important estuaries in the country from a conservation perspective, particularly in respect of its bird and fish fauna.  The extensive floodplain that surrounds the middle and upper reaches of the system make it unique in the south-western Cape.

Early days when the first Portuguese set foot on land to get freshwater for their long journey to India, the Berg River estuary must have been a true paradise. Birds, fish, hippos, elephants ... The Portuguese called the river Santiago after Sant’ Iago (St. James the Great) patron saint of Spain.  But the explorers send out by Van Riebeeck named the river Berg, and Santiago vanished.

Historically, the Berg River was one of many habitats in the Cape inhabited by hippos but, in the late 1600's, hunters began over-exploiting the hippos for their meat and hides, resulting in a decline in their numbers. By the mid-1700's, they had declined to such an extent that governor Tulbagh introduced a fine of 1000 guilders for anyone caught killing a hippo. 

Despite this protection, their numbers continued to dwindle as human settlement altered and destroyed their habitat. By the early 1800's, perhaps only a dozen remained, sheltering in the region of Kersefontein and the estuary. In 1829, only six hippos remained. The last known hippo was shot in 1869 by Martin Melck when it attacked and killed one of his employees.

Since the Europeans have settled here on farms and in, what later developed into small towns, things have changed drastically. The river and estuary were put under pressure.  Mounting pressures that are nowadays threatening this estuary, include freshwater abstraction and pollution, over fishing, housing developments and high intensity recreation.

Based on the extent of tidal influence, the estuary is estimated to be 65 km long, although seawater does not penetrate this far upstream.  The main channel at Velddrif is about 100-200m wide, becoming progressively narrower and shallower upstream.  Depth is about 3-5m on average, but can be as much as 9m in places.  In the catchment area - completely in the winter rain zone of the Western Cape, there are 3 dams: Wemmershoek-, Voëlvlei- and Berg Rivier Dam.  Smaller farm dams are also in the catchment area.

The small town of Laaiplek lies directly north of the river mouth, with Port Owen and Velddrif a bit more upstream.  This is where you'll find most of the population of the area of about 15 000.  Economic activities associated with the estuary have historically been fishery-based (commercial fishing, fish processing factories and boat repair facilities) but have recently expanded to include tourism and recreation. Cerebos and smaller commercial salt works generate further income in the area.

The ecological functioning of the estuary is determined by seasonal changes in the river discharge and consequent changes in salinity and turbidity.  In winter, when the floods recede in spring, the salinity increases and the system shifts back to a predominantly marine environment.  When the shallow pools on the floodplain start to dry out, also in spring, there is a marked increase in the number of birds the wetland supports.  The floodplain encompasses eight major wetland types in addition to the river channel, ephemeral pans, commercial salt pans, reed marsh, sedge marsh, salt marsh, halophytic floodplain, xeric floodplain and inter-tidal mudflats.

Fish are particularly reliant on estuaries for sheltered habitat on Southern Africa, and different species depend on them to different extents.   A total of 35 fish species from 30 families have been recorded in the Berg River estuary, of which nearly 50% can be regarded as either partially or completely dependent on the estuary for their survival.  These include some highly valuable species such as white steenbras and elf as well as lower value species such as grunters and harders.  The estuaries on the west coast, particularly the Berg River are crucial in maintaining the range and stock integrity of estuarine dependent species along the west coast.  The decline in the harder stock and marine gill net fishery catches on the west coast has been attributed to recruitment over-fishing in the Berg and Olifant's estuary gill net fisheries.  However, strong recoveries in fish abundance in the Berg River have been observed since gill netting in this estuary was banned in 2003.

Birds are one of the most important components of the Berg River estuary`s biodiversity.  It supports the highest recorded density of shorebirds on the West Coast of Africa, and supports nationally important populations of several species.  Since 1975 approximately 250 bird species have been recorded.  On average more than 12 000 non-passerine waterbirds are found at the estuary during summer and 6000 during winter.  In combination, the estuary and floodplain regularly support more than 20 000 birds.  In December 1992 a count of both habitats yielded 46 234 waterbirds.  The total waterbird numbers are strongly influenced by the influx of Palearctic migrants and more than 8000 migrant waders, especially Curlew Sandpiper and Little Stint are regularly present.  The open mudflats support a small population of African Black Oystercatcher.  In recent years, a large cormorant roost (estimates of up to 60 000) has developed near the mouth, probably a result of loss of suitable areas elsewhere.

The Berg River Estuary contributes about 60% of the estuarine habitat on the west coast and is thus extremely important in this respect.  The principal threat to this estuary stems from inadequate water flow volumes and an unnatural flow regime of fresh water coming down the Berg River from its catchment due to high levels of water abstraction along the river`s course and to the Berg River Dam which supplies water to the Greater Cape Town metropolitan area.  A second threat is hyper-salinity in the estuary, which occurs when the sediments at the river mouth are dredged to allow boats access to what has become a fully constructed harbour in place of the natural estuary and river mouth.  Dredging increases the velocity of the tidal flow, the turbidity of the water and the penetration of saltwater upstream and intensifies erosion within the system.

The Berg River estuary's rich biodiversity is threatened by different factors like tourism, poachers, alien vegetation e.g. Eucalyptus, water hyacinth and farming methods.  To keep an eye on everything, Cape Nature has appointed a marine estuary ranger, who, apart from conducting regular patrols on the river and estuary, also carries out law enforcement duties, biodiversity monitoring and environmental  education and public awareness work.  He is supported by the Berg River Estuary Forum.

The Berg River Estuary is sufficiently important to satisfy the criteria for registration with the Ramsar Convention. We are hopeful that this beautiful part of our country can also now receive the formal protection it deserves.