[[Image:Rainwater_harvesting_icon.png{{Language-box|right]]__NOTOC__[[Image:akkerman.jpgenglish_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 |thumbhindi_link=वाटर पोर्टल / वर्षाजल संचयन / छत वर्षाजल संचयन |rightmalayalam_link=മേല്ക്കൂരയില് നിന്നും മഴവെള്ള സംഭരണം|300pxtamil_link=coming soon |A rainwater capture system from a small household.]]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}}
Rainwater harvesting refers to structures like homes or schools, which catch rainwater and store it in underground or above-ground tanks for later use. 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 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[[Image:Rainwater_harvesting_icon. png|right|100px|]]
[[Image: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. ===Introduction===
In many cases, groundwater or surface water may be unavailable for drinking water. The groundwater level may be too deep, groundwater may be contaminated with minerals and chemicals such as arsenic or salt, surface water may be contaminated with faeces or chemicals. In these cases, rainwater harvesting can be an effective and low-cost solution.
Another option is to use water from different sources. Water that is salty or has arsenic might still be good enough for washing and sanitary purposes. High-quality rainwater, caught and stored in a tank can then be used for drinking and cooking.
===Suitable conditions===
Rainwater harvesting requires at least an annual rainfall of 100-200 mm. Many places in Latin America have rainfalls of about 500 millimeters per year.
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| valign="top" | - Possible in almost any climate <br>
===Resilience to changes in the environment===
====Drought====
Making cement in regards to drought: [[Concrete production and drought]].
===Construction, operation operations & maintenance===[[Image:rooftop catchment.jpg|thumb|right|200px|Rooftop catchment. Drawing: WHO.]]
====Catchment & storage tanks====
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:Filterrainwater capture2.jpg|thumb|right|300px200px|Filtering the water coming Two houses are connected to a rainwater capture unit, then a spout provided from the guttertank.Photo: [http://ispafrica.org 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====
====Shared roofs====
Operation and maintenance (O&M) of shared roofs have more challenges. Rooftop-harvesting systems at schools, for instance, may lose water from taps left dripping. Padlocks are often needed to ensure careful control over the water supply. Ideally, one person should be responsible for overseeing the regular cleaning and occasional repair of the system, control of water use, etc. One option is to sell the water, which ensures income for O&M and for organizing water use. Where households have installed a communal system (e.g. where several roofs are connected to one tank), the users may want to establish a water committee to manage O&M activities. The activities may include collecting fees, and controlling the caretaker’s work and the water used by each family. External agents can play a role in the following O&M areas:<br>— monitoring the condition of the system and the water quality; <br>— providing access to credit facilities for buying or replacing a system; <br>— training users/caretakers for management and O&M; <br>— training local craftsmen to carry out larger repairs. Brikke and Bredero, in their publication ''[http://http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CC0QFjAB&url=http%3A%2F%2Fwww.who.int%2Fwater_sanitation_health%2Fhygiene%2Fom%2Flinkingintro.pdf&ei=cwJpT-zaO-OiiQKCst2rBw&usg=AFQjCNEWOQhTgF3a7lzhuw5OA2KmbVGxcA&sig2=Rt2EURUyGVqDcwFg6p0xAw Linking technology choice with operation and maintenance in the context of community water supply and sanitation: A reference document for planners and project staff]'', recommend the following O&M activities in the two charts below:<br>
[[File:RolesOandM.jpg]] [[File|thumb|none|500px| Chart:OandMWHO.jpg<ref name="WHO 1"/>]]
====Potential problems====
* financial investment needed is not affordable - households or communities cannot afford to construct a suitable tank and adequate roofing.
===Costs==Comparison of costs=
Comparison of costs
* [[Brick cement tank]] of 6 m3: 3 bags of cement, 300 bricks, 3 kg of wire US$ 40
* [[Brick cement tank]] of 1 m3: 1 bag of cement, 100 bricks, 1 kg of wire US$ 20
* [[Plastic-lined tank]] of 5 m3: US$ 50
* Sub-surface [[Classical ferrocement tank|ferro-cement tank]] of 60 m3: US$ 1,900
The bigger the volume of the storage tank, the lower the material demand (and thus costs) for construction per m3 of tank volume.
In Southern Africa, US$ 320 for a system with 11 m of galvanized iron gutter; a 1.3 m3 galvanized iron tank; downpiping; tap and filters; cost does not include transportation. Where roofs are not suitable for water harvesting, the cost of roof improvement and gutters will have to be added to the cost of a tank. Such costs varied from US$ 4 per m2 (Kenya, subsidized) to US$ 12 per m2 .<ref name="WHO 1">Brikke, François, and Bredero, Maarten. ''[http://www.washdoc.info/docsearch/title/117705 Linking technology choice with operation and maintenance in the context of community water supply and sanitation: A reference document for planners and project staff]''. World Health Organization and IRC Water and Sanitation Centre. Geneva, Switzerland 2003.</ref>
===Field experiences===* Rainwater harvesting is a technology which is extremely flexible and adaptable to a wide variety of settings, it is used in the richest and poorest societies on the planet, and in the wettest and driest regions of the world.* In Ocara, Brazil, rainwater tanks have been constructed of concrete blocks. * A low-cost option is the [[brick cement tank]], used in for example Nicaragua and Ghana.
In Ocara, Brazil, ====Akvo RSR projects====The following projects utilize rooftop rainwater tanks have been constructed of concrete blocksharvesting. <br>{|style="border: 2px solid #e0e0e0; width: 100%; text-align: justify; background-color: #e9f5fd;" cellpadding="2"A low|- style="vertical-cost option is the align: top"|[[brick cement tankImage:akvorsr logo_lite.png|center|60px|link=http://akvo.org/products/rsr/]], used |- style="vertical-align: bottom"|[[Image:project 790.jpg |thumb|center|140px|<font size="2"><center>[http://rsr.akvo.org/en/project/790/ RSR Project 790]<br>WaSH program in for example Nicaragua and Ghana<br>Rural Bangladesh</center></font>|link=http://rsr.akvo.org/en/project/790/]] |[[Image:project 440.jpg |thumb|center|140px|<font size="2"><center>[http://rsr.akvo.org/en/project/440/ RSR Project 440]<br>Raising awareness on rainwater harvesting</center></font>|link=http://rsr.akvo.org/en/project/440/ ]] |[[Image: rainwater harvesting for green schools.jpg|thumb|center|140px|<font size="2"><center>[http://rsr.akvo.org/en/project/2618/ RSR Project 2618]<br>Rainwater for Green Schools Initiative</center></font>|link=Manuals, videos & linkshttp://rsr.akvo.org/en/project/2618/ ]] |[[Image:project 107.jpg |thumb|center|140px|<font size="2"><center>[http://rsr.akvo.org/en/project/107/ RSR Project 107]<br>Rainwater harvesting in Guinee Bissau</center></font>|link=http://rsr.akvo.org/en/project/107/ ]] |}<br>
===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.waterlandwashdoc.netinfo/docsearch/title/169828 Smart Water Harvesting Solutions]* [http://showdownloadwww.cfm?objecttype=marknwp.hive.contentobjectsnl/_docs/Smart-solutions-3R.downloadspread.pdf&objectid=1A6A3C6B-F37A-BF86-37BCD14A087EE1C9 Smart Water Harvesting 3R Solutions]
====MoviesVideos====* [http{{#ev:youtube|sHppepLP-pk|200|left|<center><font size="3">Rainsong video</font></www.thewaterchannel.tv/index.php?optioncenter>}} {|style=com_hwdvideoshare&task=viewvideo&Itemid=53&video_id=144 "border: 1px solid #fofofo; font-size: 125%"|-|{{#ev:youtube|6KaPjPospAk|200|auto|<center>Rainwater Harvesting Nepal, <br>by BSP-Nepal]</center>}}* [http|{{#ev:youtube|QaTYxX_jajs|200|auto|<center>Combating fluorosis - <br>Harvesting rooftop rainwater<//www.center>}}|{{#ev:youtube.com/watch?v=QaTYxX_jajs Rooftop |wWnhYIIKY0U|200|auto|<center>Rainwater harvesting India], by Zenrainman, [http:<br>Pushpam Singh<//www.rainwaterclub.org], documenting the Sachetana programme of the government of Karnataka, India.center>}} *[http|{{#ev://www.youtube.com|SCNr2Ung0cc|200|auto|<center>Rooftop rainwater - <br>Bangalore rural district</watch?v=wWnhYIIKY0U Indian movie by CSE (www.cseindia.org) promoting use of rainwater harvesting]center>}} |}
====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]]
===References===<references/> ===Acknowledgements===* Brikke, François, and Bredero, Maarten. ''[http://www.googlewashdoc.cominfo/docsearch/title/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CC0QFjAB&url=http%3A%2F%2Fwww.who.int%2Fwater_sanitation_health%2Fhygiene%2Fom%2Flinkingintro.pdf&ei=cwJpT-zaO-OiiQKCst2rBw&usg=AFQjCNEWOQhTgF3a7lzhuw5OA2KmbVGxcA&sig2=Rt2EURUyGVqDcwFg6p0xAw 117705 Linking technology choice with operation and maintenance in the context of community water supply and sanitation: A reference document for planners and project staff]''or ([http://www.who.int/water_sanitation_health/hygiene/om/wsh9241562153/en/ alternative link]). World Health Organization and IRC Water and Sanitation Centre. Geneva, Switzerland 2003.* CARE Nederland, Desk Study [[Resilient WASH systems in drought-prone areas]]. October 2010.