Roof top rainwater collection
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CTA. 2007. Roof top rainwater collection. Rural Radio Resource Pack 07/1. Wageningen, The Netherlands: CTA.
Permanent link to cite or share this item: http://hdl.handle.net/10568/57320
A civil engineer explains how low-cost guttering and ponds can enable a family to harvest significant quantities of water from their roof.
Cue: When heavy rains fall, how much water goes to waste? Water that pours off roofs, forming muddy streams that flow down the streets, eventually finding their way to a drainage ditch or a river, or collecting in pools which slowly evaporate. That rainwater is a resource, one which could be used for drinking, cooking, washing and cleaning, or even to support income generation through crops or livestock production. Roof top rainwater harvesting is one method of ensuring that at least some of the rain is put to use. Simple systems to channel rain from roofs into storage tanks can be installed at very little cost, and constructed from locally available materials. A storage tank, for example, may just be a clay-lined pit, and a gutter can easily be made from a bamboo pole. Ellen Mangore is a civil engineer who specialises in water resources. She spoke to Busani Bafana, explaining first what the basic ingredients of a roof top rainwater harvesting system are. IN: ?Basically this system consists of ? OUT: ? specialises in groundwater resources.? DUR?N: 3?33? BACK ANNOUNCEMENT: And that was Busani Bafana reporting from Bulawayo in Zimbabwe. The interview comes from a radio resource pack produced by CTA. Transcript Mangore Basically this system consists of three main components, the catchment, the conveyance and the storage. The catchment is mainly a roof which can be corrugated, thatch or asbestos and the conveyance is mainly the down-water pipe, the gutters. And the storage can be a tank; a plastic tank, a steel tank or even store it in a masonry tank underground. Bafana What is this water used for? Mangore In a rural set up we normally use it for domestic purposes, which can be cooking, cleaning and agricultural purposes, basically irrigation, livestock watering. Bafana So if a farmer is using this water to grow crops, what kind of crops would be most suitable? Mangore Usually orchards and vegetables, because we cannot actually expect to water very large fields with water that is collected off a roof. It is actually used as a supplementary supply, not that we actually depend on water that is harvested from a roof for all our requirements. Bafana I also want to find out how can we keep this water clean, should a farmer decide to use it for domestic purposes? Mangore Normally the catchment area or the conveyance system and storage system have to be kept clean, especially towards the fall of the rains. So you need to clean up just before the rains fall and we discard the first water that is collected after the first rains, use it perhaps just for irrigation, not for domestic purposes. Bafana Is it possible to have this system on a traditional hut or it applies only on a modern type of roof? Mangore It is possible but the quantity of water is decreased. Bafana How can then this system be adapted using locally available materials? Mangore For conveyance, we can use bamboo or animal skin and actually you can store the water in masonry tanks which are brick and mortar tanks built underground. Bafana If, say, in a rural setting you do not have mortar, what can you use? Mangore You can actually dig small ponds in a nearby area, and then you line it with clay, which is a material which is locally available most of the time. Bafana Are there any ways that this system can be improved on, maybe so that a farmer can collect more water or have a greater storage capacity? Mangore This system can be improved on by? you decrease seepage into the ground if you use ponds, by using an appropriate method for lining. Bafana Are there any other simple small-scale storm water harvesting techniques that farmers can use when they cannot afford gutters? Mangore Farmers can actually harvest water from the courtyard where, by virtue of the compaction of people moving around the home, then that ground is compacted, then it can act as a catchment area and it drains perhaps into a hand dug pond somewhere near the homestead. Bafana From your research in the techniques of storm water harvesting, what lessons would you say have been learnt using the rooftop technique? Mangore The rooftop technique is actually simple and low cost and it does not require much skill, so it is applicable almost everywhere this type of roof exists. Bafana Which time is it most cost effective to install this system? Mangore This system should be installed as part of a house when it is designed. As we decide to build a house we should bear in mind, because of the region in which you are building ? if this is a dry region or one where the rainfall is very seasonal then we have to consider this as part of the design of our house. Bafana There you are listeners, I was speaking to Miss Ellen Mangore, a civil engineer who specialises in groundwater resources. End of track.
- CTA Rural Radio