[[Image:Rainwater_harvesting_icon.png{{Language-box|right]]__NOTOC__english_link=Water Portal / 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 Harvesting / Rooftop 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:akkerman.jpg|thumbfrench_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 |rightkorean_link=지붕 빗물 수집 |300pxchinese_link=屋顶雨水收集 |A women using her water storage tank in Guinnee-Bissau. Photo: Paul Akkerman]]indonesian_link=Pemanenan air hujan dengan teknik atap bangunan |japanese_link=屋上雨水貯留}}
[[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.
Different catchment types are usedThe good thing about rainwater is that it falls on your own roof, and is almost always of excellent quality. Several studies have shown that water from well-maintained and covered rooftop tanks generally meets drinking water quality standards. It enables households as well as community buildings, schools and clinics to manage their own water supply for drinking water, domestic use, and income 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, such and as roof catchmentfetching water on cold, paved surface catchmentwet and slippery days is particularly unpleasant, surface catchment even this small yield is highly valued. In Uganda and riverbed catchmentSri 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 stored during 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 is needed to bridge dry periods <br>|} ===Resilience to changes in the environment=== ====Drought===='''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 too expensive for volumes of water to outlast extended dry periods. <br>'''To increase resiliency of WASH system:''' Promote smaller tank structures so they are more manageable to construct and cover, while being more affordable to families; Reduce seepage due to poor construction & siting; Follow proper concreting guidelines (see drought effects on cement, below); Make tanks from cheaper lower quality materials and repair more often; Design the outlet of the tank so that there is no dead storage; Ensure the catchment itself is efficient (e.g. gutters); Improve access to micro-finance; Support the capacity of the wet season using one government or private sector to be able to provide (for payment) a tankering scheme. ====Drought effects on cement tanks===='''Effects of drought''': Badly made concrete and cracked linings (e.g. in tanks, dams, waterways, wells, and other structures). <br>'''Underlying causes of effects''': Less water used for curing; Impure water used for mixing. <br>'''To increase resiliency of several methodsWASH system''': Ensure adequate mixing, egratios, purity of ingredients; Minimize water content in mixture; Ensure adequate curing. an More information on managing drought: [[underground tankResilient WASH systems in drought-prone areas]], .<br>Making cement in regards to drought: [[wire-cement tankConcrete production and drought]]. ===Construction, sand dam or operations & maintenance===[[plastic-lined tankImage:rooftop catchment.jpg|thumb|right|200px|Rooftop catchment. Drawing: WHO.]], until the water is needed in the dry season.
Several pump systems ====Catchment & storage tanks====The flow of water can then 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 the tankground 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 raises the water up to table in a local area or is spread across a height of 30 mwider area depends on soil conditions.
==History If using storage tanks, structures made with ferrocement or brick-cement are the best and social context==Rainwater falls on your own roofcheapest options, and they can be made locally. When a water tank is below ground, it is almost always of excellent qualitycalled a cistern. It enables people to manage their own water supply and provides Among the different storage types are the luxury [[underground tank]], [[Classical ferrocement tank | ferrocement tank]], [[plastic-lined tank]], etc. The size of “water without walking”the tank is a compromise between cost, relieving the burden volume of water carryingused, particularly for women and childrenthe length of the dry season, etc. This convenience It is available at every house on which rain fallsadvisable 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, whether on for example with a mountain top [[rope pump]] or an island in with a salt sea[[deep well pump]], which can elevate water up to a height of 30 m.
A ====Keeping the water clean====Roof rainwater harvesting system might be is usually of good quality and does not require treatment before consumption. If the house has a 500 cubic meter underground storage tankchimney, serving a whole communityhowever, or it might be just a bucketis possible that the water becomes smoky. High chimneys are therefore preferred. Water is collected through roof gutters made of PVC, bamboo, standing underneath a roof without a gutteretc. and stored. Each 20 litre container of clean The most important thing to ensure water might save quality is a kilometers long walk to the nearest source of clean watergood lid, keeping out light and as fetching water on coldinsects, wet and slippery days is particularly unpleasanta filter, even this small yield is highly valuedkeeping out all kinds of dirt. A concrete lid protects the tank from pollution. In Uganda and Sri Lanka, rainwater is traditionally collected Small fishes can be kept in the tank to keep it free from trees, using banana leaves or stems as temporary guttersinsects.
It 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 a technology which because runoff is extremely flexible contaminated with dust, leaves, insects and adaptable to bird droppings. To prevent the use of dirty water, the runoff is then led through a wide variety small filter of settingsgravel, sand and charcoal before entering the storage tank, it or a filter is used in placed between the richest catchment structure and poorest societies on the planetstorage tank. Where there is no foul-flush device, and in the wettest and driest regions user or caretaker has to divert away the first 20 litres at the start of the worldevery rainstorm.
==Suitable conditions ==The EMAS filtration system ===={{procontable [[Image:rainwater capture2.jpg|thumb|right| pro=- Possible in almost any climate <br>- Rainwater is good quality water <br>200px| con= - Storage is needed Two houses are connected to bridge dry periods<br>}}a rainwater capture unit, then a spout provided from the tank. Photo: [http://ispafrica.org Insieme Si Puo' in Africa]]]
==Technical specification==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.
====Operation====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]]. 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 system should be also checked and cleaned after every dry period of more than one month. The outsides of metal tanks may need to be painted about once a year. Leaks have to be repaired throughout the year, especially from leaking tanks and taps, as they present health risks. Chlorination of the 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 rightfully.
Basic water quality testing is recommended during the first year, with further testing when water quality is in doubt. A low cost water test is the ‘HACH’ test, about US$1 per test. If contamination is suspected or when water quality needs to be guaranteed, the water can be treated in several ways.
====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.<br>
[[File:OandM.jpg|thumb|none|500px| Chart: WHO. <ref name="WHO 1"/>]]
====Potential problems====
* corrosion of metal roofs, gutters, etc.;
* the foul-flush diverter fails because maintenance was neglected;
* taps leak at the reservoir and there are problems with the handpumps;
* contamination of uncovered tanks, especially where water is abstracted with a rope and bucket;
* unprotected tanks may provide a breeding place for mosquitoes, which may increase the danger of vector-borne disease;
* system may not fulfill drinking-water needs, during certain periods of the year, 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.
===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
====Manufacturing ====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==Cost=="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>
==Country =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.
==Manuals==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>
==Movies=Manuals, videos, and links=======Manuals====* Download the book [http://www.thewaterchannelircwash.tvorg/index.php?option=com_hwdvideoshare&task=viewvideo&Itemid=53&video_id=144 Rainwater resources/roofwater-harvesting-handbook-practitioners "Roofwater Harvesting Nepal, by BSP-Nepal: A Handbook for Practitioners"]from IRC.* Booklet [http://www.youtubewashdoc.cominfo/watch?v=QaTYxX_jajs Rooftop Rainwater harvesting Indiadocsearch/title/169828 Smart Water Harvesting Solutions], by Zenrainman, * [http://www.rainwaterclubnwp.org], documenting the Sachetana programme of the government of Karnataka, India.* [http:nl/_docs/nlSmart-solutions-3R.youtubespread.com/watch?v=4xtMnE9Bo6s Rain water advocacy movie produced by CSE, Indiapdf 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/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.rainwaterharvestingeng.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://cseindia.org /content/catch-water-where-it-falls-toolkit-urban-rainwater-harvesting Catch Water Where It Falls - Toolkit on Urban Rainwater Harvesting]* [[Solution_of_the_week_5|Akvo solution of the week 5]] ===References===<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.int/water_sanitation_health/hygiene/om/wsh9241562153/en/ alternative link]). World Health Organization and IRC Water and Sanitation Centre. Geneva, Switzerland 2003.{{Joinus}}* CARE Nederland, Desk Study [[Resilient WASH systems in drought-prone areas]]. October 2010.