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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 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.
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.
{{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>
}}
{| 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 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 WASH system''': Ensure adequate mixing, ratios, purity of ingredients; Minimize water content in mixture; Ensure adequate curing.
More information on managing drought: [[Resilient WASH systems in drought-prone areas]].<br>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.
====OperationKeeping the water clean====The flow 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 can be intercepted in different waysbecomes smoky. Different catchment types High chimneys are used, such as therefore preferred. Water is collected through roof catchmentgutters made of PVC, paved surface catchmentbamboo, surface catchment etc. and riverbed catchmentstored. Once the The most important thing to ensure water has been intercepted, it quality is led to a storage tank. Usuallygood lid, keeping out light and insects, and a filter is placed between , keeping out all kinds of dirt. A concrete lid protects the catchment structure and tank from pollution. Small fishes can be kept in the storage tankto keep it free from insects.
Roof rainwater is usually A foul-flush device or detachable down-pipe can be fitted that allows the first 20 litres of good quality and does not require treatment before consumption. If the house has runoff from a chimney, it is however possible that storm to be diverted from the water becomes smokystorage tanks. High chimneys are therefore preferred. Water This is because runoff is collected through roof gutters made of PVCcontaminated with dust, bambooleaves, etc. insects and storedbird droppings. The most important thing to ensure To prevent the use of dirty water quality , the runoff is then led through a good lidsmall filter of gravel, keeping out light sand and insectscharcoal before entering the storage tank, and or a filteris placed between the catchment structure and the storage tank. Where there is no foul-flush device, keeping out all kinds the user or caretaker has to divert away the first 20 litres at the start of dirtevery rainstorm.
Basic water quality testing is recommended during the first year, with further testing when water quality is in doubt====The EMAS filtration system ====[[Image:rainwater capture2. A low cost water test is the ‘HACH’ test, about US$1 per test. If contamination is suspected or when water quality needs jpg|thumb|right|200px|Two houses are connected to be guaranteeda rainwater capture unit, then a spout provided from the water can be treated tank. Photo: [http://ispafrica.org Insieme Si Puo' in several ways. Africa]]]
Several pump systems can be 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 to lift , it is collected through a regular gutter. To filter the water from underground tanks, for example with at the bottom of the gutter, a [[rope pump]] pitcher or ferrocement tank is placed, with a [[deep well pump]]an outlet pipe. A synthetic cloth bag is attached to the rim of the pitcher using an iron ring or wire, which can elevate water up to a height of 30 mfits around the edge. The bag should be cleaned every 3 months.
====EMAS system====[[Image:Filter.jpg|thumb|right|150px|Filtering the As water coming from the gutter]]The EMAS system for rainfall collection uses various EMAS technologies as well as simple tools begins to collect, to convert rainwater into usable drinking avoid too much garbage collecting here, first some amount of water. If roof rainwater is being useddeflected, it is collected through a regular gutteralong with most of the garbage. To filter the Hereafter, watercan be directly sent to an [[EMAS cistern]]. It is advisable for multiple cisterns to be available for storage, at depending on the bottom size of the gutter, roof. Connect one cistern at a pitcher or ferrocement tank is placed, with an time to the outlet pipe. A synthetic cloth bag is attached to the rim of the pitcher From here water can be pumped and distributed using an iron ring or wire which fits around the edgea regular EMAS pump. The bag should pump can also be cleaned every 3 monthsconnected to faucets and tanks around the house.
As water begins ====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 collect, be painted about once a year. Leaks have to avoid too much garbage collecting herebe repaired throughout the year, first some amount of water is deflectedespecially from leaking tanks and taps, along with most as they present health risks. Chlorination of the garbage. Hereafter, water can may be directly sent to an [[EMAS Cistern ]]necessary. It  Removal of debris and overhanging vegetation from gutters and the roof is advisable for multiple cisterns important to be available for storage, depending on prevent the size 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 rooffirst year, with further testing when water quality is in doubt. Connect one cistern at a time to A low cost water test is the outlet pipe‘HACH’ test, about US$1 per test. From here If contamination is suspected or when water can quality needs to be pumped and distributed using a regular EMAS pump. The pump guaranteed, the water can also be connected to faucets and tanks around the housetreated in several ways.
====MaintenanceShared roofs====Removal Operation and maintenance (O&M) of debris and overhanging vegetation shared roofs have more challenges. Rooftop-harvesting systems at schools, for instance, may lose water from gutters 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 roof system, control of water use, etc. One option is important to prevent 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 gutter being cloggedwater used by each family. Tank maintenance consists External agents can play a role in the following O&M areas:<br>— monitoring the condition of physical inspection the system and repairing cracks with cementthe 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"/>]]
Several studies have shown that ====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 from well-maintained is abstracted with a rope and covered rooftop bucket; * unprotected tanks generally meets may provide a breeding place for mosquitoes, which may increase the danger of vector-borne disease; * system may not fulfill drinking -water quality standards if maintained rightfulyneeds, 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.
====Manufacture=Costs===It is advisable to first construct a small 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 before attempting a large one.]] of 5 m3: US$ 50 A concrete lid protects the * Sub-surface [[Classical ferrocement tank from pollution. Small fishes can be kept in the |ferro-cement tank to keep it free from insects.]] of 60 m3: US$ 1,900
==Cost==Comparison The bigger the volume of costs* [[Brick cement the storage tank]] of 6 m3: 3 bags of cement, 300 bricks, 3 kg of wire US$ 40* [[Brick cement tank]] of 1 the lower the material demand (and thus costs) for construction per m3: 1 bag of cement, 100 bricks, 1 kg of wire US$ 20* [[Plastic-lined tank]] of 5 m3: US$ 50 * Sub-surface ferro-cement tank of 60 m3: US$ 1,900volume.
The bigger the volume In Southern Africa, US$ 320 for a system with 11 m of the storage 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 lower cost of roof improvement and gutters will have to be added to the material demand cost of a tank. Such costs varied from US$ 4 per m2 (and thus costsKenya, subsidized) for construction to US$ 12 per m3 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 tank volumecommunity 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.
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/]]|- 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], used <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 example Nicaragua and GhanaGreen 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.ircircwash.nlorg/pageresources/37471 Download the book 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:/showdownload.cfm?objecttype=mark/www.hivenwp.contentobjectsnl/_docs/Smart-solutions-3R.downloadspread.pdf&objectid=1A6A3C6B-F37A-BF86-37BCD14A087EE1C9 Booklet Smart Water Harvesting 3R Solutions]
==Movies==* [http://www.thewaterchannel.tv/index.php?optionVideos=com_hwdvideoshare&task=viewvideo&Itemid=53&video_id=144 Rainwater Harvesting Nepal, by BSP-Nepal]* [http{{#ev://www.youtube.com/watch?v|sHppepLP-pk|200|left|<center><font size=QaTYxX_jajs Rooftop Rainwater harvesting India], by Zenrainman, [http:"3">Rainsong video</font></www.rainwaterclub.org], documenting the Sachetana programme of the government of Karnataka, India.*[http://www.youtube.com/watch?v=wWnhYIIKY0U Indian movie by CSE (www.cseindia.org) promoting use of rainwater harvesting]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-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.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.
* CARE Nederland, Desk Study [[Resilient WASH systems in drought-prone areas]]. October 2010.
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