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[[Image:Rainwater_harvesting_icon.png{{Language-box|english_link=Water Portal / Rainwater Harvesting / Rooftop rainwater harvesting | french_link=Collecte des eaux de pluie des toits |right]]__NOTOC__[[Image:akkerman.jpgspanish_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 women using her water storage tank in Guinnee-Bissau. Photo: Paul Akkerman]]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 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 and provide a household with high-quality drinking water. 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|]]
In many cases, groundwater or surface water may be unavailable for drinking water[[Image:rooftop rainwater capture.jpg|thumb|right|200px|A rainwater capture system from a small household. Photo: [http://www. 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 chemicalsjalvardhini. In these cases, rainwater harvesting can be an effective and loworg/storage-cost solution01. Several studies have shown that water from well-maintained and covered rooftop tanks generally meets drinking water quality standardsphp Jalvardhini Pratishthan.]]]
Another option is 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 from different sources. Water which is salty rooftop rainwater harvesting, where any suitable roof surface — tiles, metal sheets, plastics, but not grass or has arsenic might still palm leaf — can be good enough for washing used to intercept the flow of rainwater in combination with gutters and sanitary purposes. Highdownpipes (made from wood, bamboo, galvanized iron, or PVC) to provide a household with high-quality drinking water. A rooftop rainwaterharvesting system might be a 500 cubic meter underground storage tank, caught and stored in serving a tank can then whole community, or it might be just a bucket, standing underneath a roof without a gutter. Rainwater harvesting systems have been used for drinking since antiquity, and cookingexamples abound in all the great civilizations throughout history.
==History and social context=Introduction===Rainwater falls on your own roofIn many cases, and is almost always of excellent quality. It enables households as well as community buildings, schools and clinics to manage their own groundwater or surface water supply may be unavailable for drinking water. The groundwater level may be too deep, domestic use, groundwater may be contaminated with minerals and income generating activities. It provides the luxury of “water without walking”chemicals such as arsenic or salt, relieving the burden of surface water carrying, particularly for women and childrenmay be contaminated with faeces or chemicals. This convenience is available at every house on which rain fallsIn these cases, whether on a mountain top or rainwater harvesting can be an island in a salt seaeffective and low-cost solution.
A The good thing about rainwater harvesting system might be a 500 cubic meter underground storage tank, serving a whole community, or is that it might be just a bucketfalls on your own roof, standing underneath a roof without a gutterand is almost always of excellent quality. Each 20 litre container of clean Several studies have shown that water might save a kilometers long walk to the nearest source of clean from well-maintained and covered rooftop tanks generally meets drinking waterquality standards. It enables households as well as community buildings, schools and as fetching clinics to manage their own water supply for drinking water on cold, wet and slippery days is particularly unpleasantdomestic use, even this small yield is highly valued. In Uganda and Sri Lanka, rainwater is traditionally collected from trees, using banana leaves or stems as temporary guttersincome generating activities.
It provides the luxury of “water without walking”, relieving the burden of water carrying, particularly for women and children. Each 20 litre container of clean water might save a kilometers long walk to the nearest source of clean water, and as fetching water on cold, wet and slippery days is particularly unpleasant, even this small yield is highly valued. In Uganda and Sri Lanka, rainwater is traditionally collected from trees, using banana leaves or stems as temporary gutters. This convenience is available at every house on which rain falls, whether on a mountaintop or an island in a salty sea.  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.
It is suitable even when the roof is small. For example a 5 x 6 meters (that is to say 30 square meters) house, with 500 mm annual precipitation, receives a rainfall of 15.000 liters on its roof; this is a sufficient amount for a family formed by 5 members. 
{| border="1" cellpadding="5" cellspacing="0" align="center"|-! width="50%" style="background:#efefef;" | Advantages! style="background:#f0f8ff;" | Disadvantages|-| valign="top" | - Possible in almost any climate <br>- Rainwater generally meets drinking water quality standards, if system is well-designed and maintained| valign="top" | - Storage tanks can additionally be filled up by pumps. is needed to bridge dry periods <br>|}
{{procontable | pro=
- Possible in almost any climate <br>
- Rainwater generally meets drinking water quality standards, if system is well-designed and maintained <br>
| con=
- Storage is needed to bridge dry periods<br>
}}
==Technical specification=Resilience to changes in the environment===
====Storage tanksDrought====Generally, structures made with ferrocement, or brick-cement '''Effects of drought:''' Water storage used up. <br>'''Underlying causes of effects:''' Lack of rainfall; Leaking linings due to bad construction; Storage not sufficient for demand – tanks are the best and cheapest option, and they can be made locallytoo expensive for volumes of water to outlast extended dry periods. When a water <br>'''To increase resiliency of WASH system:''' Promote smaller tank is below ground, it is called a cistern. Among the different storage types structures so they are the [[underground tank]]more manageable to construct and cover, [[ferro-while being more affordable to families; Reduce seepage due to poor construction & siting; Follow proper concreting guidelines (see drought effects on cement tank]], [[plastic-lined tank]], etc. The size below); Make tanks from cheaper lower quality materials and repair more often; Design the outlet of the tank so that there is a compromise between cost, no dead storage; Ensure the volume of water used, catchment itself is efficient (e.g. gutters); Improve access to micro-finance; Support the length capacity of the dry season, etcgovernment or private sector to be able to provide (for payment) a tankering scheme.
The cheapest storage ====Drought effects on cement tanks===='''Effects of all is to use the ground as storage area, a technique called groundwater rechargedrought''': Badly made concrete and cracked linings (e.g. It is accomplished by letting rainwater infiltrate in the groundtanks, dams, waterways, wells, and other structures). The recharge will locally lead to a higher <br>'''Underlying causes of effects''': Less water table, from which used for curing; Impure water can be pumped up when neededused for mixing. Whether the infiltrated <br>'''To increase resiliency of WASH system''': Ensure adequate mixing, ratios, purity of ingredients; Minimize water raises the water table content in a local area or is spread across a wider area depends on soil conditionsmixture; Ensure adequate curing.
====Operation====
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. Once the water has been intercepted, it is led to a storage tank. Usually, a filter is placed between the catchment structure and the storage tank.
Roof rainwater is usually of good quality and does not require treatment before consumption. If the house has a chimney, it is however possible that the water becomes smoky. High chimneys are therefore preferredMore information on managing drought: [[Resilient WASH systems in drought-prone areas]]. Water is collected through roof gutters made of PVC, bamboo, etc. and stored. The most important thing <br>Making cement in regards to ensure water quality is a good lid, keeping out light and insects, drought: [[Concrete production and a filter, keeping out all kinds of dirtdrought]].
Basic water quality testing is recommended during the first year===Construction, with further testing when water quality is in doubtoperations & maintenance===[[Image:rooftop catchment. A low cost water test is the ‘HACH’ test, about US$1 per testjpg|thumb|right|200px|Rooftop catchment. If contamination is suspected or when water quality needs to be guaranteed, the water can be treated in several waysDrawing: WHO. ]]
Several pump systems ====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 lift use the water from underground tanksground as storage area, for example with a [[rope pump]] or with technique called groundwater recharge. It is accomplished by letting rainwater infiltrate in the ground. The recharge will locally lead to a [[deep well pump]]higher water table, from which water can elevate be pumped up when needed. Whether the infiltrated water up to raises the water table in a local area or is spread across a height of 30 mwider area depends on soil conditions.
====EMAS system====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]], [[Image:Filter.jpgClassical ferrocement tank |thumb|right|150px|Filtering the water coming from the gutterferrocement tank]], [[plastic-lined tank]], etc. 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 size of the tank is being useda compromise between cost, it is collected through a regular gutter. To filter the volume of waterused, at the bottom length of the gutterdry season, etc. It is advisable to first construct a pitcher or ferrocement small tank is placed, with an outlet pipebefore attempting a large one. Storage tanks can additionally be filled up using pumps. A synthetic cloth bag is attached Several pump systems can be used to lift the rim of the pitcher using an iron ring water from underground tanks, for example with a [[rope pump]] or wire with a [[deep well pump]], which fits around the edge. The bag should be cleaned every 3 monthscan elevate water up to a height of 30 m.
====Keeping the water clean====Roof rainwater is usually of good quality and does not require treatment before consumption. If the house has a chimney, however, it is possible that the water becomes smoky. High chimneys are therefore preferred. Water is collected through roof gutters made of PVC, bamboo, etc. and stored. The most important thing to ensure water quality is a good lid, keeping out light and insects, and a filter, keeping out all kinds of dirt. A concrete lid protects the tank from pollution. Small fishes can be kept in the tank to keep it free from insects. A foul-flush device or detachable down-pipe can be fitted that allows the first 20 litres of runoff from a storm to be diverted from the storage tanks. This is because runoff is contaminated with dust, leaves, insects and bird droppings. To prevent the use of dirty water, the runoff is then led through a small filter of gravel, sand and charcoal before entering the storage tank, or a filter is placed between the catchment structure and the storage tank. Where there is no foul-flush device, the user or caretaker has to divert away the first 20 litres at the start of every rainstorm. ====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 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 Cistern cistern]]. 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====
Removal The system should be also checked and cleaned after every dry period of more than one month. The outsides of debris and overhanging vegetation metal tanks may need to be painted about once a year. Leaks have to be repaired throughout the year, especially from gutters leaking tanks and the roof is important to prevent the gutter being cloggedtaps, as they present health risks. Tank maintenance consists Chlorination of physical inspection and repairing cracks with cementthe water may be necessary.
Removal of debris and overhanging vegetation from gutters and the roof is important to prevent the gutter being clogged. Tank maintenance consists of physical inspection and repairing cracks with cement. Several studies have shown that water from well-maintained and covered rooftop tanks generally meets drinking water quality standards if maintained rightfulyrightfully.
====Manufacture====It Basic water quality testing is advisable to recommended during the first construct a small tank before attempting a large oneyear, with further testing when water quality is in doubt.A concrete lid protects low cost water test is the tank from pollution‘HACH’ test, about US$1 per test. Small fishes If contamination is suspected or when water quality needs to be guaranteed, the water can be kept treated in the tank to keep it free from insectsseveral ways.
==Cost==Shared roofs====Comparison Operation and maintenance (O&M) of costs* [[Brick cement tank]] shared roofs have more challenges. Rooftop-harvesting systems at schools, for instance, may lose water from taps left dripping. Padlocks are often needed to ensure careful control over the water supply. Ideally, one person should be responsible for overseeing the regular cleaning and occasional repair of 6 m3: 3 bags the system, control of cementwater use, 300 bricksetc. One option is to sell the water, 3 kg of wire US$ 40* [[Brick cement 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]] of 1 m3: 1 bag of cement), 100 bricksthe users may want to establish a water committee to manage O&M activities. The activities may include collecting fees, 1 kg 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 wire US$ 20the system and the water quality; <br>— providing access to credit facilities for buying or replacing a system; <br>* [[Plastic-lined tank]] of 5 m3: US$ 50 — training users/caretakers for management and O&M; <br>* Sub-surface ferro-cement tank of 60 m3: US$ 1,900— training local craftsmen to carry out larger repairs.<br>
The bigger the volume of the storage tank, the lower the material demand (and thus costs) for construction per m3 of tank volume[[File:OandM.jpg|thumb|none|500px| Chart: WHO. <ref name="WHO 1"/>]]
==Country experiences==Potential problems====Rainwater harvesting is a technology which is extremely flexible and adaptable to a wide variety * corrosion of settingsmetal roofs, it is used in gutters, etc.; * the foul-flush diverter fails because maintenance was neglected; * taps leak at the richest reservoir and poorest societies on there are problems with the planethandpumps; * contamination of uncovered tanks, especially where water is abstracted with a rope and in bucket; * unprotected tanks may provide a breeding place for mosquitoes, which may increase the wettest and driest regions danger of vector-borne disease; * system may not fulfill drinking-water needs, during certain periods of the worldyear, making it necessary to develop other sources or to go back to traditional sources temporarily; * financial investment needed is not affordable - households or communities cannot afford to construct a suitable tank and adequate roofing.
In Ocara===Costs===Comparison of costs * [[Brick cement tank]] of 6 m3: 3 bags of cement, Brazil300 bricks, rainwater tanks have been constructed 3 kg of concrete blocks. wire US$ 40 * [[Brick cement tank]] of 1 m3: 1 bag of cement, 100 bricks, 1 kg of wire US$ 20 A low* [[Plastic-cost option is the lined tank]] of 5 m3: US$ 50 * Sub-surface [[brick Classical ferrocement tank|ferro-cement tank]]of 60 m3: US$ 1, used in for example Nicaragua and Ghana.900
==Manuals==*[http://www.irc.nl/page/37471 Download The bigger the volume of the storage tank, the lower the book "Roofwater Harvesting: A Handbook material demand (and thus costs) for Practitioners" from the IRC website]*[http://www.waterland.net/showdownload.cfm?objecttype=mark.hive.contentobjects.downloadconstruction per m3 of tank volume.pdf&objectid=1A6A3C6B-F37A-BF86-37BCD14A087EE1C9 Booklet Smart Water Harvesting Solutions]
==Movies==* [http://wwwIn 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.thewaterchannelWhere 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.tv/indexSuch costs varied from US$ 4 per m2 (Kenya, subsidized) to US$ 12 per m2.php?option<ref name=com_hwdvideoshare&task=viewvideo&Itemid=53&video_id=144 Rainwater Harvesting Nepal"WHO 1">Brikke, François, and Bredero, by BSP-Nepal]* Maarten. ''[http://www.youtubewashdoc.cominfo/watch?v=QaTYxX_jajs Rooftop Rainwater harvesting India], by Zenrainman, [http:docsearch/title/www.rainwaterclub.org], documenting 117705 Linking technology choice with operation and maintenance in the Sachetana programme context of the government of Karnataka, Indiacommunity water supply and sanitation: A reference document for planners and project staff]''.*[http://wwwWorld Health Organization and IRC Water and Sanitation Centre.youtubeGeneva, Switzerland 2003.com</watch?v=wWnhYIIKY0U Indian movie by CSE (www.cseindia.org) promoting use of rainwater harvesting]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.
====Akvo RSR projects====The following projects utilize rooftop rainwater harvesting.<br>{|style="border: 2px solid #e0e0e0; width: 100%; text-align: justify; background-color: #e9f5fd;" cellpadding="2"|- style="vertical-align: top"|[[Image:akvorsr logo_lite.png|center|60px|link=http://akvo.org/products/rsr/]]|- 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 <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=http://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.ircwash.org/resources/roofwater-harvesting-handbook-practitioners "Roofwater Harvesting: A Handbook for Practitioners"] from IRC.* 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%"|-|{{#ev:youtube|6KaPjPospAk|200|auto|<center>Rainwater Harvesting Nepal, <br>by BSP-Nepal</center>}}|{{#ev:youtube|QaTYxX_jajs|200|auto|<center>Combating fluorosis - <br>Harvesting rooftop rainwater</center>}}|{{#ev:youtube|wWnhYIIKY0U|200|auto|<center>Rainwater harvesting, <br>Pushpam Singh</center>}} |{{#ev:youtube|SCNr2Ung0cc|200|auto|<center>Rooftop rainwater - <br>Bangalore rural district</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 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 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-toolkitharvesting Catch Water Where It Falls - Toolkit on Urban Rainwater Harvesting]* [[Solution_of_the_week_5|Akvo solution of the week 5]] ===References===<references/> ===Acknowledgements===* 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] or ([http://www.who.netint/water_sanitation_health/hygiene/om/wsh9241562153/en/ Rainwater Toolkitalternative 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.
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