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Water Portal / Rainwater Harvesting / Rooftop rainwater harvesting

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{{Language-box|english_link=Water Portal / Rainwater Harvesting / Rooftop rainwater harvesting | french_link=Collecte des eaux de pluie des toits |spanish_link=Captación de Agua de Lluvia / Captación de agua de lluvia en techos | hindi_link=वाटर पोर्टल / वर्षाजल संचयन / छत वर्षाजल संचयन |malayalam_link=മേല്‍ക്കൂരയില്‍ നിന്നും മഴവെള്ള സംഭരണം|tamil_link=coming soon | korean_link=지붕 빗물 수집 | chinese_link=屋顶雨水收集 | indonesian_link=Pemanenan air hujan dengan teknik atap bangunan |japanese_link=屋上雨水貯留}}

 

[[Image:Rainwater_harvesting_icon.png|right|100px|]]

__NOTOC__ <small-title />[[Image:roof rain rooftop rainwater capture.jpg|thumb|right|200px|A rainwater capture system from a small household. Photo: [http://www.jalvardhini.org/storage-01.php Jalvardhini Pratishthan.]]]

Rainwater harvesting refers to structures like homes or schools, which catch rainwater and store it in underground or above-ground tanks for later use. One way to collect water is rooftop rainwater harvesting, where any suitable roof surface — tiles, metal sheets, plastics, but not grass or palm leaf — can be used to intercept the flow of rainwater in combination with gutters and downpipes (made from wood, bamboo, galvanized iron, or PVC) to provide a household with high-quality drinking water. A rooftop rainwater harvesting system might be a 500 cubic meter underground storage tank, serving a whole community, or it might be just a bucket, standing underneath a roof without a gutter. Rainwater harvesting systems have been used since antiquity, and examples abound in all the great civilizations throughout history.

The flow of water can be intercepted in different ways. Different catchment types are used, such as roof catchment, paved surface catchment, surface catchment and riverbed catchment. The cheapest storage of all is to use the ground as storage area, a technique called groundwater recharge. It is accomplished by letting rainwater infiltrate in the ground. The recharge will locally lead to a higher water table, from which water can be pumped up when needed. Whether the infiltrated water raises the water table in a local area or is spread across a wider area depends on soil conditions.

If using storage tanks, structures made with ferrocement or brick-cement are the best and cheapest options, and they can be made locally. When a water tank is below ground, it is called a cistern. Among the different storage types are the [[underground tank]], [[ferro-cement Classical ferrocement tank | ferrocement tank]], [[plastic-lined tank]], etc. The size of the tank is a compromise between cost, the volume of water used, the length of the dry season, etc. It is advisable to first construct a small tank before attempting a large one. Storage tanks can additionally be filled up using pumps. Several pump systems can be used to lift the water from underground tanks, for example with a [[rope pump]] or with a [[deep well pump]], which can elevate water up to a height of 30 m.

====Keeping the water clean====

====The EMAS filtration system ====

[[Image:rainwater capture2.jpg|thumb|right|200px|Two houses are connected to a rainwater capture unit, then a spout provided from the tank. Photo: [http://ispafrica.org/gallery-water.html Insieme Si Puo' in Africa]]]

The EMAS system for rainfall collection uses various EMAS technologies as well as simple tools to convert rainwater into usable drinking water. If roof rainwater is being used, it is collected through a regular gutter. To filter the water, at the bottom of the gutter, a pitcher or ferrocement tank is placed, with an outlet pipe. A synthetic cloth bag is attached to the rim of the pitcher using an iron ring or wire, which fits around the edge. The bag should be cleaned every 3 months.

As water begins to collect, to avoid too much garbage collecting here, first some amount of water is deflected, along with most of the garbage. Hereafter, water can be directly sent to an [[EMAS Cisterncistern]]. It is advisable for multiple cisterns to be available for storage, depending on the size of the roof. Connect one cistern at a time to the outlet pipe. From here water can be pumped and distributed using a regular EMAS pump. The pump can also be connected to faucets and tanks around the house.

====Maintenance====

The following projects utilize rooftop rainwater harvesting.

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===Manuals, videos, and links===

 

====Manuals====

* Download the book [http://www.ircircwash.nlorg/pageresources/37471 roofwater-harvesting-handbook-practitioners "Roofwater Harvesting: A Handbook for Practitioners"] from the IRC website.

* Booklet [http://www.washdoc.info/docsearch/title/169828 Smart Water Harvesting Solutions]

* [http://www.nwp.nl/_docs/Smart-solutions-3R.spread.pdf Smart 3R Solutions]

====Videos====

{{#ev:youtube|sHppepLP-pk|200|left|<center><font size="3">Rainsong video</font></center>}}

{|style="border: 1px solid #fofofo; font-size: 125%"

====External links====

* [http://www.rainfoundation.org Rainwater Harvesting Implementation Network (RAIN)]

* [http://practicalaction.org/energy/waterrainwater-andharvesting-sanitation/rainwater_harvesting 8 Rainwater Harvesting information on Practical Action]

* [http://www.rainwaterharvesting.org Indian website on rainwater harvesting ]

* [http://en.wikipedia.org/wiki/Rainwater_harvesting Wikipedia article on rainwater harvesting]

* [http://www.eng.warwick.ac.uk/dtu/rwh Rainwater Harvesting info on the DTU unit of University of Warwick]

* [http://web.archive.org/web/20100112111544/http://www.unep.org:80/depi/rainwater / Rainwater Partnership ]* [http://wwwcseindia.org/content/catch-water-where-it-falls-toolkit-urban-rainwater-toolkit.net/ harvesting Catch Water Where It Falls - Toolkit on Urban Rainwater ToolkitHarvesting]

* [[Solution_of_the_week_5|Akvo solution of the week 5]]

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