Rainwater harvesting and benefits

2016-05-04 06:00

THE following opinion piece was written by Mbali Mahaye of the Department of Water and Sanitation (Communications) Durban.

"In my childhood, when the elders asked me not to use more water, I thought water has unlimited resource and we shall be getting our requirement endlessly.

“At that time in each of the houses there were ponds and people were unaware of water scarcity, but now, owing to drought, overpopulation and congestion, the ponds have vanished.

“The importance of water seems to become clearer every year. People say there are five necessities of life such as fire, water, air, Earth and the sky. Among these water has to be the most essential. Water is life. Man can live without food for more than one month, but without water man cannot live more than seven days.

“Water is so precious to an extent that should there be any world wars, then the next one will be about water. We know that about 70% of the Earth's surface is covered with water. But only three percent of the water found on Earth is drinkable, the rest is in the form of sea water and ice.

“There is a great variation in the amount of water consumed per day all over the world. The minimum water intake required to maintain body hydration is 1.5 litres per day. The maintenance of comfort under normal circumstances requires three percent of mass body weight or typically about 2.3 litres per person of drinking water per day. A family in a village collects only about 10 to 15 litres for a family of six to eight members. Therefore, rainwater harvesting is the best option to ensure that they almost always have enough supply.

“The process of collecting, storing and the use of rain water from a catchment surface before it reaches the aquifer is called rainwater harvesting. Rainwater harvesting systems are simple to install and operate. Rain water can supplement the sub-soil water level and increase urban greenery.

“In some cases, rainwater may be the only available or economical water source. Rainwater harvesting systems can be simple to construct from inexpensive local materials, and are potentially successful in most habitable locations. Rainwater offers advantages in water quality for both irrigation and domestic use.

“Its naturally soft (unlike well water), contains almost no dissolved minerals or salts, is free of chemical treatment, and is a relatively reliable source of water for households. In KwaZulu-Natal, it is an old practice in high rainfall areas to collect rainwater from roof tops into storage tanks.

“In the foot hills water flowing from springs is collected by embankment type water storage.”

Rainwater can be harvested from:

• Rooftops: the collection area in most cases is the roof of a house or a building. The effective roof area and the material used in constructing the roof influence the efficiency of collection and the water quality. A conveyance system usually consists of gutters or pipes that deliver rainwater falling on the rooftop to cisterns or other storage vessels.

Both drainpipes and roof surfaces should be constructed of chemically inert materials such as wood, plastic, aluminum, or fibreglass, in order to avoid adverse effects on water quality. The water ultimately is stored in a storage tank or cistern, which should also be constructed of an inert material.

Reinforced concrete, fiberglass, or stainless steel are suitable materials. Storage tanks may be constructed as part of the building, or may be built as a separate unit located some distance away from the building.

• Storm water drains: most residential areas have a proper network of storm water drains. If maintained , these offer a simple and cost effective means for harvesting rainwater.

“One of the beauties of rainwater harvesting systems is their flexibility. A system can be as simple as a barrel placed under a rain gutter downspout for watering a garden or as complex as an engineered, multi-tank, pumped and pressurized construction to supply residential and irrigation needs. Rainwater harvesting systems are integrated with the house, which makes the water easily accessible."

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