Over the six past decades, there has been a drought cycle every six to seven years. The last time Cape Town was in adrought was 2004. I have watched this in Cape Town since 1965 when I can first remember the newspapers reporting the dam levels every day, and this has been the case to a greater or lesser extent for the past forty years.

Water tanks are devices storing harvested rain from roofs. Rainwater tanks are installed to make use of rain water for later use, reduce on ones reliance for mains water use both for economic and environmental reasons but especially to aid self-sufficiency.
Rain is really distilled water precipitating after condensing at high altitude where temperatures are low. It matters not whether water falling from the sky is rain, hail, sleet or snow, it is all water and may be harvested.
The following is a guide to rain water tanks and rainwater harvesting in South Africa.
Stored rain water may be used for watering gardens, agriculture, flushing toilets, for washing machines, both laundry and dishwashing, washing cars, and also for drinking, especially when other water supplies are unavailable, expensive, or of poor quality, and that adequate care is taken that the water is not contaminated or the water is adequately filtered.
Submerged ground rainwater tanks may also be used for retention of storm-water (water from roof and paved areas) for release at a later time, though this is not suitable for use in the home. Conventional rain water ranks are not designed simply to put underground and backfilled with soil. These will collapse and may pop out of the ground if empty. Special underground tanks are built, but are very expensive otherwise a special room may be built with a concrete floor and roof with brick walls, all of which possibly make underground tanks unviable, but if this is the only source of water may this be necessary.
Water tanks may have a high (perceived) initial cost. However, many homes use small scale rainwater tanks to harvest relatively small quantities of water for landscaping/gardening applications rather than as a potable (drinkable) water surrogate. While all need to be to screen out mosquitoes, the lack of proper filtering or closed loop systems will create breeding grounds for mosquito larvae. An example of the screening process I with the Water Rhapsody Rain Runner, which filters harvested rainwater near the gutter, and this water may then enter an underground pipe to reach a remote rainwater tank.
If water is used for drinking, it should be filtered first. Filtration (such as reverse osmosis or ultra-filtration) will remove all pathogens. (Reverse osmosis is energy hungry and for rainwater this method of filtration should never be required.) Other filtration consists of ozone and UV (ultra violet) treatment. Reports of illness associated with rainwater tanks are very infrequent, and public health studies anywhere have not identified a correlation. Rainwater is generally considered fit to drink if it smells, tastes and looks fine.
Certain paints and roofing materials may cause contamination. In particular, lead-based paints should never be used even as a primer onto metal surfaces. Tar-based coatings may affect the taste of the water. Chemically treated timbers and lead flashing should be excluded from roof catchments.
Maintenance of rainwater catchment areas includes regular removal of vegetation and debris from rain gutters. So long as a rainwater tank is kept closed to preclude light from entering, no algae will grow, so the only maintenance that needs to be done is perhaps removal of the sediment on the floor of the tank once a year.
Water tanks may be constructed from materials such as plastic (polyethylene), concrete, plastered brickwork, galvanized steel, as well as fibreglass and stainless steel which are rust and chemical-resistant. By far the most popular and cost effective rainwater ranks are the plastic polyethylene tanks which are freely available from several manufacturers. It is imperative that the tanks are opaque to prevent the exposure of stored water to sunlight, to eliminate the possibility of algal growth.
Another imperative is that rainwater tanks should have a pre-filter under the eaves like the Water Rhapsody Rain Runner to prevent debris from entering the water tank/s and also to prevent any possibility of the feed pipe from a downpipe leading to the water tank (the ring main) from blocking. This pre-filter also prevents the ingress of mosquitos.
Apart from rooftops, tanks may also be set up to collect rainwater from concrete patios, driveways and other impervious surfaces. This water though may only be used for irrigation and toilet flushing, as it may be soiled from pedestrian and other animal use.
Initial sizes typically ranged in capacity from around 200 to 10,000 litres, or multiples of these. The most popular sizes are 2500 litres and 5000 litres, which are easily handled and are not unsightly.
Smaller tanks, such as the plastic 200-liter rainwater tanks are also used in some cases. These smaller tanks are mainly used in conjunction with a Garden Rhapsody Grey Water Re-using System. With this arrangement water tanks fitted above ground may flow by gravity into the Garden Rhapsody which has a pump incorporated into it and will pump the rain / grey water onto the garden. This can even be done automatically by trickle feeding the water from the higher rain tank/s into the Garden Rhapsody at all times, so that rain water flowing into the rain tank/s will not fill a tank that is full already, no matter how small the tank is.
Larger tanks are commonly used where there is no access to a municipal water supply. In this instance at no extra charge, Water Rhapsody will recommend a tank at a house taking into consideration a whole host of factors like: roof type surface (tile or metal), roof area in square metres, number of people drawing water from the rainwater tank, whether or not one has the rest of the Water Rhapsody systems in place to reduce ones consumption, and whether the house is a home, holiday home or a commercial or industrial building. To give an example of this calculation, (this was done by actuaries for Water Rhapsody): a typical metal roof will deliver 1000 litres of water from 100 square metres of roof for every 11 mm of rain. To get the same volume of water from a tiled roof one would need 16 mm of rain. Each middle class person uses 240 litres of water daily, so the draw from the rain tanks is very substantial. If one should install only two of the Water Rhapsody Systems to say: re-use grey water and the Water Rhapsody Multi-Flush to minimize toilet flushing, one reduces the demand for water to at worst half (of the 240 litres to 120 litres per person per day), but mostly down to as little as to 80 to 100 litres per person per day. Stored Rainwater then goes so much further without a change in lifestyle. The value of this calculation ensures that there is enough storage so that rainwater tanks need never overflow, and that one does not overspend on too many rainwater tanks that never fill.
All our water supplies will dry up very soon, which makes rainwater harvesting essential. A strategy microcosm of rainwater harvesting has been used by Jeremy Westgarth –Taylor of Water Rhapsody for the area of Knysna. This area has no storage dam, and relies totally on the water flowing from a river weir. The supply of water from the weir can no longer meet demand. Jeremy’s strategy would be to force everyone to install rainwater tanks to harvest rainwater from roofs, ban outright any irrigation from any other source other than grey water, and minimize toilet flushing water. Because the area is mostly a holiday destination, the volume of stored water together with the reduction of water demand would mean that the town of Knysna would create a large dam of many individual tanks. The total volume of stored water could be as much as 70 million litres. This would mean that the need for municipal water would be needed for two or three weeks per year, at the end of each holiday season, if at all.
The strategy formula for Knysna is a microcosm of what is imperative for implementation country wide.
The following is the typical use of water from rainwater storage tanks.
Most areas have seasonal rainfall. Very few have rain all year round. Water Rhapsody has devised a system whereby water stored in rainwater tanks is use during the rain season. This applies to areas supplied with municipal water but not able to meet demand.
Amortization of the cost of installation of water tanks. Amortization (paying off the capital) of rainwater tanks with the Water Rhapsody Grand Opus is best done by filling and emptying the rainwater tank/s as often as possible. As many times as any rainwater tank/s can possibly fill from rainwater from roofs, these should be drawn down to empty to avoid them overflowing next time rain should fall. Overflowing tanks mean that there is not enough rainwater storage in place or not enough people to consume water in the house. Rainwater tanks that never fill mean that too much storage has been put into place, or that there are too many people drawing from this water.
Water outages and emergency supply. Water Rhapsody has implemented a novel approach of an emergency supply if all rain water should be exhausted. This is coupled with an emergency supply when the municipality implement water outages as a means of demand management when demand exceeds supply. This system included in the Water Rhapsody Grand Opus is a means of keeping a days supply at all times when the municipality literally switches off the water. The system is full proof to ensure that it is impossible your precious stored rainwater cannot flow out into the municipal system.
Electricity outages. Electricity outages are something that pervades our age. Water Rhapsody include in the Water Rhapsody Grand Opus an override manifold so that if the user has no UPS (uninterrupted Power Supply) water will still be able to be used from a municipal source, if this does not coincide with a water outage. By simply switching valves, one may revert to municipal water.
Water Pressures. Rainwater pumped from rainwater tanks into a house with the Water Rhapsody Grand Opus may not exceed the pressure allowed for hot water cylinders of whatever type one uses. It is for this reason that Water Rhapsody has included within the override box an adjustable pressure reducing valve to suit the needs of any hot water cylinder if one should revert to municipal water supply. Whilst the rain water is pumped into the house one is quite safe from over pressurization as the Water Rhapsody pump is set to the correct pressure too.
Without general implementation of rainwater harvesting all South African towns’ cities and villages will not be able to continue expanding QED.
Lightning. During lightning storms some nitrogen in very small quantities is dissolved into the rain. This quantity is far too small to do any harm.
Lichen. Lichen is a symbiotic relationship between a fungus and algae, and the one cannot live without the other. This tuft of very precious growth on a tiled roof is one of the best indicators of pollution. So long as lichen grows on a roof the water that falls on that roof is safe for household use. Beware if all the lichen dies. Many people think that this growth is unsightly and should be removed and the roof painted. This is not true and ill advised. Leave the lichen alone.

A climatologist from the University of South Africa (Unisa) has helped develop a low cost, eco-friendly system to harvest moisture from abundant mountain fog in a water-scarce region of the Eastern Cape, and communities there are already benefiting from it.

The project was successfully launched in Cabazane Village, in the rural Mount Ayliff area in the north of the province, in mid-March 2010 during the annual National Water Week.

The area, which falls in the picturesque Alfred Nzo district municipality, is bordered to the north by the mountain kingdom of Lesotho and much of the terrain is steep and remote, with very cold winters and mild summers. Fog is a frequent visitor and a ready source of clean water.

Professor Jana Olivier of Unisa’s School of Agriculture and Environmental Sciences has spent the past 20 years specialising in the properties and hazards associated with fog, especially for vehicles.

She later started delving into the technique of fog harvesting. “We got funding from the Water Research Commission, and we designed the fog water system,” she said.

Olivier teamed up with Professors Johan van Heerden, Hannes Rautenbach and Tinus Truter – all of Pretoria University – in the development of the system.

Unisa is involved in ongoing research into water harvesting from fog, especially for isolated rural communities, where water is scarce and villagers often have to walk vast distances to fetch a few litres at a time.

However, the system is only practical where fog occurs for at least 40 days a year, and for a period of several hours at a time.

The project has also been rolled out in other dry areas of South Africa, including Venda, Limpopo, and the West Coast, but Mount Ayliff’s persistent fog yields the best results, producing hundreds of litres of water a day.

“The West Coast and the mountainous areas – stretching from the Soutpansberg in the north, along the Drakensberg in the east to the Cape Mountains in the south – have the highest fog harvesting potential,” said Olivier.

Mount Ayliff is located in the Umzimvubu local municipality, one of two municipalities within Alfred Nzo – the other is Umzimkhulu. Umzimvubu’s population is just 198 550, of which only 4% live in towns – the rest live in rural areas.

Safe drinking water is a continual problem as the area lacks essential infrastructure, including water on tap. Villagers are often forced to dip into natural springs, running the risk of picking up water-borne disease.

“We have a challenge … because about 40% of our community here does not have basic water,” said Alfred Nzo mayor Gcinikhaya Mpumza.

However, the villagers’ lives have changed with the installation of the water-harvesting system and its inexhaustible supply. No electricity is needed to power the scheme, which makes it eco-friendly and low-cost, and suitable for areas with no power infrastructure.

Because the technology is simple, the equipment does not need special maintenance. The system consists of a double layer of 30% shade cloth nets stretched between steel cables supported by posts, with a gutter beneath each screen to catch the run-off. All components are readily available in the area.

The Cabazane set-up involves around 700 square metres of netting, said Olivier, with each square metre of shade cloth yielding up to five litres of water a day – depending on the weather.

Water droplets in the fog are trapped on the nets. They get bigger and heavier as the fog rolls along, and eventually run down into the gutter and from there through a filter into storage tanks. The system works best when the wind is blowing, because the fog moves over the nets more rapidly.

The system is installed up on the mountain slope, where nothing more than gravity is needed to get the drops flowing into the tanks. Reports say that about 30 homes in Cabazane Village have already benefited from the project.

The quality of water is described as “very high”, falling within the World Health Organisation’s standards for potable water. “The water is incredibly pure because it comes from the clouds,” said Olivier.

Innovative schemes like the simple and cost-effective fog harvester are well-suited to South Africa, as it’s one of the driest countries in the world, with annual rainfall well below the global average.

Source: MediaClubSouthAfrica.com