Water is important to almost everything on earth, from influencing our climate and weather patterns to shaping the continents and the healthy living of organisms. Two thirds of the human body is made up of water, and although we can live up to a month without food, we cannot survive without drinking water for longer than five to seven days.
Water is a basic need and a key building block of all communities. Huge amounts of fresh water are used to irrigate farmland for food production. It is essential for manufacturing, particularly in heavy industries like electricity generation plants and iron and steel production, which need large amounts of water for cooling or as a power source. A reliable supply of fresh water is critical for all households too.
Knowing exactly how much water is used in our daily lives helps us understand how important it is to use it wisely. Generally, we think about the water needed for drinking and cleaning only. However, we should also think about the water required to produce the goods we buy and the food we eat. The ‘water footprint’ is a measure of the total amount of fresh water that is used to produce goods and services. We need to understand and manage water at the source and avoid wastage from occurring before water becomes available for human use.
Water and climate change
Climate change is likely to increase our demand for water even further, particularly in already water-scarce regions like the Overberg. In Southern Africa, scientists are predicting changes in the intensity and seasonality of drought and rainfall. This means that the dry areas of our country (such as the Western Cape) will get drier, with longer periods of drought, while the much wetter eastern half of South Africa is expected to receive heavier rainfall over shorter periods, with a higher risk of flooding.
Climate change is likely to have a significant impact on water and food security. It could threaten access to sustainable, fresh drinking water and sanitation, especially for vulnerable people.
Water quality in our freshwater ecosystems is also likely to be affected by the higher temperatures brought about by climate change. Rising sea levels predicted due to melting polar ice could cause an increase in the salinity of river estuaries, resulting in changes to aquatic ecosystems. Bacterial diseases, such as cholera and diarrhoea, are more likely to spread in warmer river water. We can also expect higher water evaporation rates, which will reduce our water storage capacity.
Water availability in South Africa
The sustainable management of our freshwater resources is critical for the economic development of South Africa. We live in a naturally dry country with an average annual rainfall of 464 mm – well below the world average of 860 mm. More than 50% of our water comes from only 14% of our rivers, which are situated mainly along the eastern escarpment. In terms of water availability per person, South Africa is classified as a water-stressed country, with 98% of our water supplies already being used. Based on our current water use and population growth, the Department of Water Affairs estimates a 1,7% water shortage by 2025.
In the past, South Africa invested in building dams and treatment plants to maintain our supply of fresh water. Today, we have few viable sites left to build new storage dams, and we face serious and costly development challenges as our population and cities continue to grow.
There is generally little awareness of South Africa’s uncertain water situation. We often use water inefficiently, and water wastage is common. All of us will be negatively affected by water shortages and increasing water costs. Greater awareness, protection of freshwater resources, and effective water-saving practices are needed for us to conserve South Africa’s limited water resources.
Protecting our freshwater ecosystems
Not only do we live in a water-stressed country, but 80% of South Africa’s rivers are also classified as threatened by urban development. Human activity, such as industry, settlements and recreation, is popular along ecologically sensitive ‘green corridors’, like floodplains and wetlands, and should be carefully managed. Vleis and rivers are often used for illegal dumping and flushing of farm wastewater, chemicals and pesticides.
Runoff from informal settlements and polluted stormwater from our houses, buildings and roads are also frequently allowed to enter our rivers and wetlands untreated. Many of our urban water bodies contain dangerously high levels of bacteria, and are unhealthy for people and animals to swim in. The health of our river systems is vital to maintain our water quality and to ensure we have a sustainable supply of fresh drinking water.
Water bodies, wetlands in particular, play a very important role by controlling the flow of water, filtering impurities, and replenishing groundwater. Wetlands also naturally absorb greenhouse gases such as carbon dioxide. Natural vegetation in these areas should be protected and not removed, as it maintains biodiversity, and reduces surface runoff, soil erosion and the risk of flooding.
Threat of invasive species
Invasive alien species cost South Africa’s economy billions of rands every year. Invasive alien species are plants, animals and microbes that are brought in from other countries, and then out-compete the indigenous species for habitat and food.
Invasive alien plants directly threaten our water security, ecosystems and the productive use of our land. They intensify the impact of fires and floods, increase soil erosion, and absorb enormous amounts of water. Invasive aquatic plants, (such as the water hyacinth, parrot’s feather, water lettuce and water weed) affect agriculture, fisheries, transport, recreation and water supply.
Where does our water come from?
Most of the bulk untreated water supplied to the Overstrand comes from dams that store water running off the mountains during our winter rainfall season. Ground water is also pumped from boreholes.
Water for Hermanus (3,500 Ml per year) comes from the De Bos Dam and the Gateway well field. Further well fields at Camphill and Volmoed in the Hemel & Aarde Valley are being developed.
Kleinmond’s water source (910 Ml p.a.) is the Palmiet River, while Rooi-Els/Pringle Bay/Betty’s Bay (900 Ml p.a.) gets water from the Buffels River Dam.
To the east, Stanford (380 Ml p.a.) relies on The Eye fountain and the recently completed Koudevlakte well field. Gansbaai’s water (1,400 Ml p.a.) comes from the Kraaibosch Dam and Klipgat and Grotte Fountains. Pearly Beach water sources are the Pearly Beach Dam and Koekemoer Dam (140 Ml p.a.).
Sustainability of water sources is ensured by the water use licensing process of the Department of Water Affairs, where a license is only issued for a sustainable volume to be abstracted from a source, with very specific licensing conditions attached to it. When the volume abstracted is approaching the licensed volume for a specific source, additional sources have to be identified, planned for, and budgeted for, to be developed in time.
How sustainable is our water supply?
Even with our latest water supply schemes, the increasing water demand and threat of climate change mean the future of our water supply in the Overstrand is not secure.
In order to keep providing fresh drinking water it is necessary to conserve water. We all need to understand how scarce water is, how to protect our water resources, and use water responsibly.
How is our drinking water treated?
We take turning on a tap for fresh water for granted. But producing an uninterrupted supply of fresh drinking water is a critical non-stop operation. From storage dams or boreholes, raw (untreated) water is conveyed through pipelines and tunnels to the water treatment works, where it is made potable (fit for drinking). It is put through various processes to remove dirt and other unwanted materials, and to kill any harmful micro-organisms, ensuring it complies with the South African National Standard for Drinking Water.
At the water treatment plant, the water first passes into a stilling chamber to reduce water pressure and control water flow. From here, it enters the particle separation and settling process, which entails adding lime for pH (acidity/alkalinity) adjustment, and either ferric or aluminium sulphate to help small particles join together to form larger masses. If required, powdered activated carbon is added to reduce any taste and odour problems in the raw water that might have been caused by algae in the storage dams. Once these chemicals are added and mixed, the water is directed to larger settling tanks at even slower flows to allow the clusters of particles in the water to settle and be drawn to the bottom as sludge (sediment).
The clear water at the top flows through slots in the tank, and is chlorinated before it passes through the sand filter beds. The filtered water is stabilised by adding further lime and carbon dioxide to ensure that the water is not corrosive (containing harmful chemicals) and does not form scales. A final dose of chlorine is added for disinfection as the water leaves the water treatment plant for the bulk storage reservoir, before being discharged to households, industry, business and agriculture.
In the Overstrand the surface water has a brown colour, produced by tannins in fynbos through which the water flows. The main challenge to be dealt with is this brown colour of the raw water. The treatment process to improve the colour includes coagulation, flocculation, sedimentation, filtration, stabilization, and disinfection.
In the case of groundwater sources, the main quality issues are the high iron and manganese content. This is reduced by dosing oxidising chemicals, followed by filtration. At Hermanus a new bio-filtration plant is under construction, which will treat the iron and manganese in a more natural way.
The entire process of water catchment, treatment, storage, distribution and management is subjected annually to the Department of Water Affair’s Blue Drop certification process for drinking water. This is a strict set of standards that ensures that we receive high-quality drinking water. The Overstrand has consistently scored high on the Blue Drop assessment and contributed to Hermanus winning the Greenest Town in South Africa title for the past two years running.
Where does our wastewater go?
Wastewater produced by households and industry is removed from properties through a sewerage system. This is a network of pipelines and pump stations conveying wastewater to the City’s wastewater treatment works, where the water is put through mostly mechanical and biological processes to break down and remove substances that could be harmful to human beings and the environment.
In the Overstrand 2,500 Ml of sewage is treated every year.
The treated effluent is released into the natural environment via rivers and streams, which eventually flow into the ocean. Some of the treated water in Hermanus is used to irrigate the golf course and sports fields. Grey water is also used for irrigation in Gansbaai, and is being considered for Stanford. The further treatment of waste water to potable standard is being considered for Hermanus for the future. The beneficial use of sewerage sludge for e.g. energy production will be considered in future, although volumes are relatively low.
The entire sewerage treatment process is annually subjected to the Department of Water Affairs’ stringent Green Drop certification process for wastewater. Once again, the Overstrand’s Green Drop scores are very high.