The freshwater biome can be categorized into lakes, streams and wetlands, and all are interconnected. We depend utterly on freshwater systems that globally comprise only 0.8% of all the water on the planet and cover only 1/5 of the Earth’s surface.

South Africa is a water-scarce country with rainfall distributed unevenly across the country and with fluctuating seasonal extremes. Conserving our water resources is critical for our wellbeing and for our survival.

The freshwater biome is characterised by flowing water (such as streams and rivers), relatively stationary water bodies (such as lakes and pans) and wetlands (such as marshes and swampy ground). These freshwater bodies and ecosystems are interconnected and dependent on a variety of factors including climate and rainfall, and a healthy biodiversity.

Rivers and freshwater systems in general are also under threat from a variety of human activities, and in South Africa these include pollution from fertilizer and mining activities and from malfunctioning waste water treatment plants and untreated runoff, such as from paved areas. Over-extraction from streams and rivers and from boreholes, and due to water wasted through leaks in the water supply systems also threaten our water resources.

The headlands of many river systems are in mountainous regions. This stream is forming in a grassy wetland high up in the mountain kingdom of Lesotho. Lesotho, through the Lesotho Highlands Water Project – involving a system of dams and tunnels – exports an enormous quantity of water to South Africa much of which ultimately feeds the greater Johannesburg area

Bio-diverse high-altitude wetlands prevent soil erosion, act as water purification systems and are essential for the functioning of water catchment systems.

Where artificial dams are not a factor, water from mountain catchment areas finds its way into streams that flow downhill to contribute to the lower lying river systems. This photo of a small waterfall was taken in the Drakensberg mountains just below Sani Pass, which traverses from KwaZulu-Natal into Lesotho.

The source of the Mkomazi River (also known as the Umkomaas) is in the Drakensberg mountains, and here it is flowing through the Highover Wildlife Sanctuary (Richmond in KwaZulu-Natal) as it makes its way towards the Indian Ocean. As rivers progress away from their source they collect nutrient-rich organic debris that feeds many of the organisms living in the flowing waters.

This view looks down to the Umgeni (or Mgeni) River at the Cumberland Nature Reserve near Pietermaritzburg. The Umgeni River rises in the Dargle area of the KwaZulu-Natal Midlands and flows for 232 km (144 miles) to the port city of Durban on the Indian Ocean. This section in the photo is after the river has been joined by the Msunduzi River, which is a major tributary.

After good rains, water was overflowing the wall of the Midmar Dam in March 2019. The Midmar Dam near Howick is one of four major dams on the Umgeni River system. Just above the dam, the Lions River, which is significantly augmented by water transferred artificially from the Spring Grove Dam, boosts the water supply into the Umgeni catchment system.

Just downstream from the Midmar Dam the waters of the Umgeni River fall 95 m (310 feet) into the gorge below. The power of the Howick Falls is dependent on the amount of water released from the Midmar Dam.

By contrast to the rivers in the well-vegetated Midlands of KwaZulu-Natal, the Gariep (Orange) River, which rises in the Drakensburg mountains in Lesotho, flows west through arid regions on its journey towards the Atlantic Ocean. This photograph was taken of the river at a comparatively low level as it flows placidly through the widening gorge below the famous Augrabies Falls in the Northern Cape.

And in a further contrast, this view is of the sandy course of the meandering Black Imfolozi (Umfolozi) River near the Sonthuli Loop in the Imfolozi section of the Hluhuwe-Imfolozi Park in KwaZulu-Natal. Elephants are foraging on the shore and on the far bank two buffalo are enjoying the afternoon sun while a group of five white rhinos are disappearing into the bush after having crossed the river. Frequently in the dry winter season the river can be reduced to a mere trickle, and sometimes it is completely dry.

However, after torrential rains in the catchment area the river can rise rapidly and roar through the valley even ripping up trees on its banks. But in this photo taken from a low-level bridge, a reasonably full Black Imfolozi River can be seen flowing smoothly and rapidly towards the confluence with the White Imfolozi. Thereafter the river is known simply as the Imfolozi River as it continues on its course towards the Indian Ocean at the mouth of the St Lucia Estuary.

The relatively small Nzimane river in the Hluhluwe section of the Hluhuwe-Imfolozi Park flows fast at the end of the wet season in March. The diversity of the dense vegetation complete with palm trees always makes me think that this river looks rather like the Hollywood notion of an African river. This photo was taken looking downstream from a low-level bridge

And of course, according to legend at least, no African river is complete without crocodiles basking on its banks. This Nile crocodile, trying to absorb some warmth on a fairly overcast day, I photographed from near the same low-level bridge as in the previous photo, but looking upstream.

Next week, I will showcase some of KwaZulu-Natal’s freshwater lakes and pans.

P.S. Usually posts are published on Thursdays, but sometimes I am late, so I apologise for that.


Sources:

BioExpedition. 2015. Freshwater Biome.  https://www.bioexpedition.com/freshwater-biome/

SANBI. 2019. SA’s wetlands and rivers are crucial for water security. South African National Biodiversity Institute (SANBI). 16 October. https://www.sanbi.org/news/sas-wetlands-and-rivers-are-crucial-for-water-security/

WWF. 2013. An introduction to South Africa’s Water Resource Areas. WWF Report ZA . https://www.journeyofwater.co.za/files/wwf_sa_watersource_area10_lo.pdf


Posted by Carol