I was recently asked in which direction rivers flow in South Africa. My initial answer was that most rivers flow either west towards the Atlantic Ocean, or east towards to Indian Ocean. This was based on a childhood memory of being taught the crocodiles and hippos occur, in South Africa, only in east-flowing rivers. I decided to investigate this a little further and discovered that, although my theories and what I was taught is not wrong, the facts are a little more complicated than that. In fact, so complicated and interesting that I decided to do a series on our rivers to highlight some of the most interesting facts. We will start with getting familiar with some of the generally used terminology.
When you think about it, all rivers probably flow in all directions at some point, but the general direction of flow is determined between the point of origin of the river, the source or the head waters, and the point where it either joins a larger river, or flow into the ocean. If a river joins another river, the smaller river is generally referred to as a tributary to the larger river, for example, the second largest river in SA, the Vaal River, is a tributary to the largest river, the Orange River. The point at which the river joins the ocean is called the mouth of the river, for example the well-known Storms River Mouth in the Eastern Cape. In many cases this forms an estuary, a relatively flat area where fresh water from the river mixes with salt water from the ocean creating a very unique ecosystem that is particularly rich in biodiversity. An example of this is the Saint Lucia estuary located in the iSimangoliso Wetland Park (in KwaZulu Natal) that has been declared a UNESCO World Heritage Site. This is one of the largest and most diverse estuarine ecosystems in Africa and definitely warrants its own article at a later stage.
The rivers in SA all start either from a collection of very small tributaries in the mountains, or from an eye or fountain where water naturally seeps out of the ground. The direction of flow is mainly influenced in SA by the mountain ranges that split the country roughly in two. The Drakensberg extends from the Limpopo and Mpumalanga provinces in the northeast, through Kwa-Zulu Natal, Lesotho and into the Eastern province in the southwest. Here it joins with the south-western Cape mountain ranges that runs east and north through the Western Cape and Northern Cape provinces. All our rivers start in or near the mountains and then flows east, south, or west toward the Atlantic or Indian Oceans.
We have 10 major rivers in South Africa namely the Orange, Limpopo, Vaal, Thukela, Olifants, Gamtoos, Great Kei, Komati, Great Fish and Molopo Rivers. As I travel through the country over the next few weeks, I will discuss the interesting facts about the rivers that I crossed, and also the ones that I may not have the privilege to cross personally.
Written by Dr. Helen Prinsloo
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