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{{short description|Accumulation of rainwater for reuse}}
[[Image:Johad.JPG|thumb|View of a Johad at village [[Thathawata]]]]
[[File:RWH-image.jpg|thumb|upright=1.5| configuration of domestic rainwater harvesting system in Uganda.<ref name="Staddon-2018">{{Cite journal |last1=Staddon |first1=Chad |last2=Rogers |first2=Josh |last3=Warriner |first3=Calum |last4=Ward |first4=Sarah |last5=Powell |first5=Wayne |date=2018-11-17 |title=Why doesn't every family practice rainwater harvesting? Factors that affect the decision to adopt rainwater harvesting as a household water security strategy in central Uganda |journal=Water International |language=en |volume=43 |issue=8 |pages=1114–1135 |doi=10.1080/02508060.2018.1535417 |s2cid=158857347 |issn=0250-8060|doi-access=free |bibcode=2018WatIn..43.1114S }}</ref>]]
[[Image:Bawdi.jpg|thumb|View of a stepwell at [[Fatehpur, Shekhawati]]. This one featured in the movie [[Paheli]] ]]
'''Rainwater harvesting''' ('''RWH''') is the collection and storage of [[rain]], rather than allowing it to run off. Rainwater is collected from a roof-like surface and redirected to a [[Rainwater tank|tank]], [[cistern]], deep pit ([[well]], shaft, or [[borehole]]), [[Aquifer storage and recovery|aquifer]], or a [[reservoir]] with [[percolation]], so that it seeps down and restores the ground water. Rainwater harvesting differs from [[stormwater harvesting]] as the runoff is typically collected from roofs and other area surfaces for storage and subsequent reuse.<ref name="NSW Managing Urban Stormwater">{{Cite report |lang=en |title=Managing Urban Stormwater: Harvesting and reuse |date=1 April 2006 |publisher=[[New South Wales Department of Environment and Conservation]] |publication-place=Sydney, Australia |isbn=1-74137-875-3 |url=https://www.environment.nsw.gov.au/-/media/OEH/Corporate-Site/Documents/Water/Water-quality/managing-urban-stormwater-harvesting-reuse-060137.pdf |archive-url=https://web.archive.org/web/20200716180541/https://www.environment.nsw.gov.au/-/media/OEH/Corporate-Site/Documents/Water/Water-quality/managing-urban-stormwater-harvesting-reuse-060137.pdf |archive-date=2020-07-16}}</ref>{{rp|10}} Its uses include watering gardens, [[livestock]],<ref>{{Cite web|url=https://www.ntotank.com/blog/rainwater-harvesting-for-livestock/|title=Rainwater Harvesting for Livestock|website=www.ntotank.com|access-date=2018-11-21|archive-date=2018-11-21|archive-url=https://web.archive.org/web/20181121120251/https://www.ntotank.com/blog/rainwater-harvesting-for-livestock/|url-status=live}}</ref> [[irrigation]], [[Drinking water|domestic use]] with proper treatment, and domestic heating. The harvested water can also be used for long-term storage or [[groundwater recharge]].<ref>{{Cite book|last=Kinkade-Levario|first=Heather|title=Design for Water : Rainwater Harvesting, Stormwater Catchment, and Alternate Water Reuse|publisher=New Society Publishers|year=2007|isbn=978-0-86571-580-6|location=Gabriola Island, B.C.|pages=27|language=en}}</ref>


Rainwater harvesting is one of the simplest and oldest methods of [[Self-supply of water and sanitation|self-supply of water]] for households, having been used in South Asia and other countries for many thousands of years.<ref>{{cite book |last1=Bagel |first1=Ravi |last2=Stepan |first2=Lea |last3=Hill |first3=Joseph K.W. |title=Water, knowledge and the environment in Asia : epistemologies, practices and locales |date=2017 |location=London |isbn=9781315543161}}</ref> Installations can be designed for different scales, including households, neighborhoods, and communities, and can also serve institutions such as schools, hospitals, and other public facilities.<ref>{{Cite web |url=http://www.rural-water-supply.net/en/self-supply |title=Rural Water Supply Network Self-supply site |last=Rural Water Supply Network |website=www.rural-water-supply.net/en/self-supply |access-date=2017-03-19 |archive-date=2019-01-14 |archive-url=https://web.archive.org/web/20190114211852/http://www.rural-water-supply.net/en/self-supply |url-status=live }}</ref>
'''Rainwater harvesting''' is the gathering, or accumulating and storing, of rainwater. <ref>[http://www.harvesth2o.com/faq.shtml Definition of rainwater harvesting]</ref>


== Uses ==
Traditionally, rainwater harvesting has been practiced in arid and semi-arid areas, and has provided drinking water, domestic water, water for [[livestock]], water for small [[irrigation]] and a way to replenish [[ground water]] levels.
[[File:03242012Taller sostenibilidad lore037.jpg|thumb|upright=1.2|Rainwater capture and storage system, Mexico City campus,<!-- C. Puente 222, Coapa, Arboledas del Sur, Tlalpan, 14380 Ciudad de México, CDMX, Mexico --> [[Monterrey Institute of Technology and Higher Education#Campuses by region|Monterrey Institute of Technology and Higher Education]]]]
[[File:Cistern in the Mission District, San Francisco, California.jpg|thumb|[[Cistern]], [[Mission District, San Francisco]], California]]
[[File:Gibraltar East Side Water Catchments in 1992.jpg|thumb|Rainwater capture, [[Gibraltar]] East Side, 1992]]
[[File:Panarea01.jpg|thumb|Home, with rain collection jars on roof, [[Panarea]], [[Aeolian Islands]], north of [[Sicily]], [[Italy]]<ref>[[:it:Architettura eoliana]]</ref>]]
[[File:UDDT with rainwater harvesting (3441547910).jpg|thumb|upright|Rainwater harvesting and hand washing system for a toilet in Kenya. ]]
[[File:Rainwater harvesting in Burkina Faso (2957138439).jpg|thumb|Rainwater harvesting in [[Burkina Faso]]]]
[[File:Rainwater Harvesting and Plastic Pond 2.JPG|thumb|Plastic Pond for Rainwater Harvesting, [[Nepal]], 2013<ref>[[:commons:Category:Rainwater harvesting in Nepal]]</ref>]]
[[File:Rainwater harvesting systems in Kiribati (10715703914).jpg|thumb|Rainwater harvesting system, [[Kiribati]] ]]


==Use around the world ==
=== Domestic use ===
Rooftop rainwater harvesting is used to provide drinking water, domestic water, water for livestock, water for small irrigation, and a way to replenish groundwater levels.
Currently in China and Brazil, rooftop rainwater harvesting is being practised for use for all the above purposes. [[Gansu]] province in China and semi-arid
[[Northeast Region, Brazil|north east Brazil]] have the largest rooftop rainwater harvesting projects ongoing.


Kenya has already been successfully harvesting rainwater for toilets, laundry, and irrigation. Since the establishment of the 2016 Water Act, Kenya has prioritized regulating its agriculture industry.<ref>{{Cite web|title=Understanding the Kenya 2016 Water Act|url=https://www.2030wrg.org/wp-content/uploads/2016/12/Understanding-the-Kenyan-Water-Act-2016.pdf|url-status=live|access-date=July 26, 2021|website=2030wrg|archive-date=July 26, 2021|archive-url=https://web.archive.org/web/20210726195032/https://www.2030wrg.org/wp-content/uploads/2016/12/Understanding-the-Kenyan-Water-Act-2016.pdf}}</ref> Additionally, areas in Australia use harvested rainwater for cooking and drinking.<ref name="Amos 174–190">{{Cite journal|last1=Amos|first1=Caleb Christian|last2=Rahman|first2=Ataur|last3=Karim|first3=Fazlul|last4=Gathenya|first4=John Mwangi|date=November 2018|title=A scoping review of roof harvested rainwater usage in urban agriculture: Australia and Kenya in focus|journal=Journal of Cleaner Production|volume=202|pages=174–190|doi=10.1016/j.jclepro.2018.08.108|bibcode=2018JCPro.202..174A |s2cid=158718294|issn=0959-6526}}</ref> Studies by Stout et al. on the feasibility of RWH in India found it most beneficial for small-scale irrigation, which provides income from produce sales, and for groundwater recharge.<ref name="Amos 174–190"/>
In [[Bermuda]], the law requires all new construction to include rainwater harvesting adequate for the residents.
The [[U.S. Virgin Islands]] has a similar law


=== Agriculture ===
In [[Indus Valley Civilization]], Elephanta Caves and Kanheri Caves in [[Mumbai]] rainwater harvesting alone has been used to supply in their water requirements.
In regards to urban agriculture, rainwater harvesting in urban areas reduces the impact of runoff and flooding. The combination of urban 'green' rooftops with rainwater catchments have been found to reduce building temperatures by more than 1.3 degrees Celsius. Rainwater harvesting in conjunction with urban agriculture would be a viable way to help meet the United Nations [[Sustainable Development Goals]] for cleaner and sustainable cities, health and wellbeing, and food and [[water security]] ([[Sustainable Development Goal 6]]). The technology is available, however, it needs to be remodeled in order to use water more efficiently, especially in an urban setting.


Missions to five Caribbean countries have shown that the capture and storage of rainwater runoff for later use is able to significantly reduce the risk of losing some or all of the year's harvest because of soil or [[water scarcity]]. In addition, the risks associated with flooding and soil erosion during high rainfall seasons would decrease. Small farmers, especially those farming on hillsides, could benefit the most from rainwater harvesting because they are able to capture runoff and decrease the effects of soil erosion.<ref name="Fletcher-Paul-2018">{{Cite journal|last=Fletcher-Paul|first=Dr. Lystra|title=Feasibility Study of Rainwater Harvesting for Agriculture in the Caribbean Subregion|url=http://www.fao.org/3/a-bq747e.pdf|journal=FAO|access-date=2018-04-25|archive-date=2018-04-25|archive-url=https://web.archive.org/web/20180425184846/http://www.fao.org/3/a-bq747e.pdf|url-status=live}}</ref>
In [[Senegal]]/Guinea-Bissau, the houses of the [[Diola]]-people are frequently equipped with homebrew rainwater harvesters made from local, organic material.


Many countries, especially those with arid environments, use rainwater harvesting as a cheap and reliable source of clean water.<ref>{{Cite book|last=Zhu|first=Qiang|title=Rainwater Harvesting for Agriculture and Water Supply|publisher=Springer|year=2015|isbn=978-981-287-964-6|location=Beijing|pages=20|display-authors=etal}}</ref> To enhance [[irrigation]] in arid environments, ridges of soil are constructed to trap and prevent rainwater from running down hills and slopes. Even in periods of low [[rainfall]], enough water is collected for crops to grow.<ref name="PracticalAction-2019">{{Cite web|title=Rainwater harvesting|url=http://practicalaction.org/rainwater-harvesting-8|access-date=2016-03-03|archive-date=2019-05-08|archive-url=https://web.archive.org/web/20190508110251/https://practicalaction.org/rainwater-harvesting-8|url-status=dead}}</ref> Water can be collected from roofs, dams and ponds can be constructed to hold large quantities of rainwater so that even on days when little to no rainfall occurs, enough is available to irrigate crops.
In the [[United Kingdom]] [[water butts]] are oft-found in domestic gardens to collect rainwater which is then used to water the garden.


=== Industry ===
In [[Colorado]], water rights laws severely restrict rainwater harvesting -- a property owner who captures rainwater is effectively stealing it from those who have rights to take water from the watershed.<ref>[http://www.ext.colostate.edu/pubs/natres/06702.html Graywater Reuse and Rainwater Harvesting in Colorado]</ref>


[[Frankfurt Airport]] has the largest rainwater harvesting system in Germany, saving approximately 1 million cubic meters of water per year. The cost of the system was 1.5 million dm (US$63,000) in 1993. This system collects water from the roofs of the new terminal which has an area of 26,800 square meters. The water is collected in the basement of the airport in six tanks with a storage capacity of 100 cubic meters. The water is mainly used for toilet flushing, watering plants and cleaning the air conditioning system.<ref>{{Cite web|title=Rainwater harvesting in Germany|url=http://www.rainwaterharvesting.org/international/germany.htm|url-status=live|access-date=2018-04-24|website=www.rainwaterharvesting.org|archive-date=2019-02-19|archive-url=https://web.archive.org/web/20190219135902/http://www.rainwaterharvesting.org/international/germany.htm}}</ref>
==Advantages in urban areas==
Rainwater harvesting in urban areas can have manifold reasons. To provide supplemental water for the city's requirement, to increase soil moisture levels for urban greenery, to increase the ground water table through artificial recharge, to mitigate urban flooding and to improve the quality of groundwater are some of the reasons why rainwater harvesting can be adopted in cities.
In urban areas of the developed world, at a household level, harvested rainwater can be used for flushing toilets and washing laundry. Indeed in [[hard water]] areas it is superior to mains water for this. It can also be used for showering or bathing. It may require treatment prior to use for drinking.


Rainwater harvesting was adopted at The Velodrome – The [[Olympic Park, London|London Olympic Park]] – in order to increase the sustainability of the facility. A 73% decrease in potable water demand by the park was estimated. Despite this, it was deemed that rainwater harvesting was a less efficient use of financial resources to increase sustainability than the park's [[Blackwater (waste)|blackwater]] recycling program.<ref name="ODA-2011">{{Cite web|date=2011|title=Learning legacy: Lessons learned from the London 2012 Games construction project|url=http://learninglegacy.independent.gov.uk/documents/pdfs/sustainability/154-rainwater-harvesting-sust.pdf|website=Olympic Delivery Authority|access-date=2018-04-24|archive-date=2015-12-08|archive-url=https://web.archive.org/web/20151208062004/http://learninglegacy.independent.gov.uk/documents/pdfs/sustainability/154-rainwater-harvesting-sust.pdf|url-status=live}}</ref>
Two residences in the city of [[Toronto]], [[Canada]], use treated harvested rainwater for drinking water, and reuse water (i.e. treated wastewater) for all other household water applications including toilet flushing, bathing, showers, laundry, and garden irrigation ([http://healthyhousesystem.com/toronto.html Toronto Healthy House]).


== Technologies ==
In [[New Zealand]], many houses away from the larger towns and cities routinely rely on rainwater collected from roofs as the only source of water for all household activities. This is almost inevitably the case for many [[holiday home]]s.
Traditionally, stormwater management using [[detention basins]] served a single purpose. However, [[OptiRTC|optimized real-time control]] lets this infrastructure double as a source of rainwater harvesting without compromising the existing detention capacity.<ref>{{Cite web |url=http://www.high-profile.com/rainwater-harvesting-controls-in-cloud-by-steve-roy-marcus-quigley-and-chuck-raymond/ |title=Rainwater Harvesting - Controls in the Cloud |work=M. C.
|access-date=11 January 2015 |date=2013-10-03 |archive-date=2019-08-05 |archive-url=https://web.archive.org/web/20190805142833/https://www.high-profile.com/rainwater-harvesting-controls-in-cloud-by-steve-roy-marcus-quigley-and-chuck-raymond/ |url-status=live }}</ref> This has been used in the [[EPA]] headquarters to evacuate stored water prior to storm events, thus reducing wet weather flow while ensuring water availability for later reuse. This has the benefit of increasing water quality released and decreasing the volume of water released during [[combined sewer overflow]] events.<ref>{{Cite web |url=https://money.cnn.com/gallery/technology/2014/11/11/innovative-city-tech/8.html |title=The Tech Behind Smart Cities - Eliminating Water Pollution |last=O'Brien |first=Sara Ashley |work=CNN Money |access-date=13 November 2014 |date=2014-11-11 |archive-date=2014-11-14 |archive-url=https://web.archive.org/web/20141114145530/http://money.cnn.com/gallery/technology/2014/11/11/innovative-city-tech/8.html |url-status=live }}</ref><ref>{{Cite web |url=http://www1.villanova.edu/content/dam/villanova/engineering/vcase/sym-presentations/3a3_Making%20Green_Andrea%20Braga.pdf |title=Making Green Work, and Work Harder |last=Braga |first=Andrea |publisher=Geosyntec |pages=5 |access-date=30 November 2014 |archive-date=4 March 2016 |archive-url=https://web.archive.org/web/20160304195602/http://www1.villanova.edu/content/dam/villanova/engineering/vcase/sym-presentations/3a3_Making%20Green_Andrea%20Braga.pdf |url-status=dead }}</ref>


Generally, [[check dam]]s are constructed across the streams to enhance the percolation of surface water into the [[subsoil]] strata. The water percolation in the water-impounded area of the check dams can be enhanced artificially manyfold by loosening the subsoil strata and [[ANFO]] explosives as used in [[open cast mining]]. Thus, local [[aquifer]]s can be recharged quickly using the available surface water fully for use in the dry season.
==Systems==
[[Image:Rainwater harvesting system.JPG|thumb|right|150px|A domestic rainwater harvesting system]] There are many types of systems to harvest rainwater. The type used depends greatly on the purpose (domestic or industrial use) and to some extent also on physical and human considerations.


=== System setup ===
==Domestic rainwater systems==
Rainwater harvesting systems can range in complexity, from systems that can be installed with minimal skills, to automated systems that require advanced setup and installation. The basic rainwater harvesting system is more of a plumbing job than a technical job, as all the outlets from the building's terrace are connected through a pipe to an underground tank that stores water. There are common components that are installed in such systems, such as pre-filters (see e.g. [[vortex filter]]), drains/gutters, storage containers, and depending on whether the system is pressurized, also pumps, and treatment devices such as UV lights, chlorination devices and post-filtration equipment.
===System types===
At the moment, 2 types of systems are generally used. These include [[diy|homebrew systems]] and [[commercial]] systems. Both of these systems are known under the term [[Rainwater_tank|water harvester]]s and require only a limited amount of knowledge to set up (if basic systems are used). In both cases, the system consists of a [[storage tank|storage tank]] to store the water and piping (to guide the water in). Additionally, extra pressuring equipment as [[pressure vessel]]s, [[inline pump controller]]s or [[pressure sensitive pump]]s may also be required. <ref>[http://www.harvesth2o.com/pumps_or_tanks.shtml Pressurising equipment sometimes required for rainwater collection systems]</ref> Finally, water purifying equipment as water-purifying [[plant]]s, [[UV-light]]s or [[distillation]] equipment are sometimes (depending on local conditions <ref>[http://www.harvesth2o.com/faq.shtml Water treatments sometimes not needed]</ref> ) added to purify the collected water. The system is then called a [[Greywater|Greywater treatment system]]. Greywater systems are usually preferred over regular water harvesters as they allow the system to not only treat the rainwater, but water from other sources as well (eg the [[watercloset]]; if plants are used). However, this feature may also be averted by using a [[UV-lamp]] and [[composting toilet]] instead.


Systems are ideally sized to meet the water demand throughout the dry season since it must be big enough to support daily water consumption. Specifically, the rainfall capturing area such as a building roof must be large enough to maintain an adequate flow of water. The water storage tank size should be large enough to contain the captured water.
Depending on local circumstances however, a [[gravity]]-fed system may already be enough to have a pressured water collection system. <ref>[http://www.harvesth2o.com/faq.shtml Gravity-fed system trough height difference also sometimes enough for pressured water collection system]</ref> In the latter case, no pumps/pressure vessels are thus required to have a pressured system. In practice, gravity-controlled systems are usually created by placing the [[Rainwater_tank|water harvester]] on an elevation (eg rooftops).
For low-tech systems, many low-tech methods are used to capture rainwater: rooftop systems, surface water capture, and pumping the rainwater that has already soaked into the ground or captured in reservoirs and storing it in tanks (cisterns).


=== Rainwater harvesting by solar power panels ===
====DIY domestic systems====
Good quality water resources near populated areas are becoming scarce and costly for consumers. In addition to solar and wind energy, rainwater is a major [[renewable resource]] for any land. Vast areas are being covered by [[Photovoltaics|solar PV panels]] every year in all parts of the world. Solar panels can also be used for harvesting most of the rainwater falling on them and drinking quality water, free from bacteria and suspended matter, can be generated by simple [[Water purification|filtration and disinfection]] processes as rainwater is very low in [[salinity]].<ref>{{Cite web |url=http://www.windpowerengineering.com/environmental/wind-solar-powered-offgridbox-useful-hurricane-passes/ |title=Rain fed solar-powered water purification systems. |access-date=21 October 2017 |archive-date=21 October 2017 |archive-url=https://web.archive.org/web/20171021111651/http://www.windpowerengineering.com/environmental/wind-solar-powered-offgridbox-useful-hurricane-passes/ |url-status=live }}</ref><ref>{{Cite web |url=https://cleantechnica.com/2017/12/04/inverted-umbrella-brings-clean-water-clean-power-india/ |title=Inverted Umbrella Brings Clean Water & Clean Power To India |access-date=5 December 2017 |date=2017-12-04 |archive-date=2018-07-09 |archive-url=https://web.archive.org/web/20180709123311/https://cleantechnica.com/2017/12/04/inverted-umbrella-brings-clean-water-clean-power-india/ |url-status=live }}</ref><ref name="inh">{{cite web |url=https://inhabitat.com/new-rooftop-solar-hydropanels-harvest-drinking-water-and-energy-at-the-same-time/ |title=New rooftop solar hydro panels harvest drinking water and energy at the same time |date=29 November 2017 |access-date=2017-11-30 |archive-date=2019-08-10 |archive-url=https://web.archive.org/web/20190810113041/https://inhabitat.com/new-rooftop-solar-hydropanels-harvest-drinking-water-and-energy-at-the-same-time/ |url-status=live }}</ref> Exploiting rainwater for value-added products like bottled drinking water makes solar PV power plants profitable even in high rainfall or cloudy areas by generating additional income. Recently, cost-effective rainwater collection in existing wells has been found highly effective in raising groundwater levels in India.
As water conservation is becoming more and more popular, more people have begun to make their own homebrew installation. These systems range from traditional technologies like rain barrels to more complex greywater systems. Through the internet, plans and accurate construction information have become available. <ref>[http://www.green-trust.org/2007/11/well-on-hold-lets-go-roofwater.html Roofwater harvesting information (ebooks, ...)]</ref> <ref>[http://www.villageearth.org/pages/Appropriate_Technology/ATSourcebook/Watersupply.php VillageEarth Water harvesting information]</ref> <ref>[http://www.builditsolar.com/Projects/Water/Water.htm Concrete list of DIY-rainwater harvester systems and how to build them]</ref> Depending on the degree of personal skill and preference, a more basic (regular water tank and piping) <ref>[http://www.thefarm.org/charities/i4at/surv/raincat.htm The Farm's DIY gravity-fed rainwater harvester]</ref>) -or more advanced (eg pressured systems with water treatment, ...) -system is chosen.


=== Other innovations ===
====Commercial domestic systems====
The [[Groasis Waterboxx]] is an example of low scale technology, in this case to assist planting of trees in arid area. It harvests rainwater and dew.
Commercial systems are also made. They are offered by a variety of companies which include [[Rain Man (company)|Rain Man]], ... Commercial rain harvesters can be obtained in both pressurized <ref>[http://www.bbc.co.uk/leicester/content/articles/2006/06/21/rainwater_recycling_hazelton_feature.shtml Rainman water harvesters system operation]</ref> as gravity-fed systems <ref>[http://www.independent.co.uk/life-style/house-and-home/property/donnachadh-mccarthy-the-home-ecologist-461540.html Gravity-fed rain harvester]</ref>. Greywater treatment systems are sold by companies as [[Water Works UK]], [[Nubian Water Systems]], [[BRAC Systems]], ... <ref>[http://peswiki.com/index.php/Directory:Home_Generation:Gray_Water_Recycling Other commercial rain water harvesting systems]</ref> Again, they are available in pressurised as gravity-fed systems.<ref>[http://barinya.com/australia/environment/Grey_Water_Systems_Australia.htm Greywater systems aviable in gravity-fed as pressurised form]</ref> <ref>[http://www.aridsolutionsinc.com/page/page/4243373.htm Example of gravity-fed greywater system]</ref>


== Advantages ==
===System's operation===
Rainwater harvesting provides the independent water supply during regional water restrictions, and in developed countries, it is often used to supplement the main supply. It provides water when a drought occurs, can help mitigate flooding of low-lying areas, and reduces demand on wells which may enable groundwater levels to be sustained. Rainwater harvesting increases the availability of water during dry seasons by increasing the levels of dried borewells and wells. Surface water supply is readily available for various purposes thus reducing dependence on underground water. It improves the quality of ground by diluting salinity. It does not cause pollution and is environmentally friendly. It is cost-effective and easily affordable. It also helps in the availability of potable water, as rainwater is substantially free of salinity and other salts. Applications of rainwater harvesting in [[Integrated urban water management|urban water system]] provides a substantial benefit for both [[water supply]] and [[wastewater]] subsystems by reducing the need for [[clean water]] in water distribution systems, less generated [[stormwater]] in [[sewer system]]s,<ref>{{Cite journal |last1=Behzadian |first1=k |last2=Kapelan |first2=Z |date=2015 |title=Advantages of integrated and sustainability based assessment for metabolism-based strategic planning of urban water systems |journal=Science of the Total Environment |volume=527-528 |pages=220–231 |doi=10.1016/j.scitotenv.2015.04.097 |pmid= 25965035|hdl=10871/17351 |url=https://ore.exeter.ac.uk/repository/bitstream/10871/17351/1/Behzadian%20and%20Kapelan%202015b.pdf |bibcode=2015ScTEn.527..220B |hdl-access=free }}</ref> and a reduction in stormwater runoff polluting freshwater bodies.
A mechanism can be used to send the initial water flow to waste, usually the first few liters. These are commonly known as [http://www.rain-barrel.net/first-flush.html 'first-flush'] diverters, and are used to increase the chance that the large-particle residue that might accumulate on your collection surface is washed away from (and not into) your [[storage tank]]. Such a system also compensates for the fact that the ''initial'' minutes of a rainfall can include airborne pollutants being washed from the sky{{Fact|date=February 2007}}, and likewise minimizes contamination of your captured supply. Simple but regular inspection and maintenance of such a device is usually necessary.


A large body of work has focused on the development of life cycle assessment and its costing methodologies to assess the level of environmental impacts and money that can be saved by implementing rainwater harvesting systems.<ref name="inh" />
Not all catchment systems use such a feature. For example, rainwater in rural areas of Australia is traditionally used without such a system, and without treatment,{{Fact|date=February 2007}} but this may be unwise in different environments.<!--"may be unwise" is vague.-->


=== Independent water supply ===
==Industrial systems==
Rainwater harvesting provides an independent water supply during water restrictions. In areas where clean water is costly, or difficult to come by, rainwater harvesting is a critical source of clean water. In developed countries, rainwater is often harvested to be used as a supplemental source of water rather than the main source, but the harvesting of rainwater can also decrease a household's water costs or overall usage levels. Rainwater is safe to drink if the consumers do additional treatments before drinking. Boiling water helps to kill germs. Adding another supplement to the system such as a [[first flush]] diverter is also a common procedure to avoid contaminants of the water.<ref>Centers of Disease Control and Prevention (CDC), 2013 Retrieved from https://www.cdc.gov/healthywater/drinking/private/rainwater-collection.html {{Webarchive|url=https://web.archive.org/web/20200406004255/https://www.cdc.gov/healthywater/drinking/private/rainwater-collection.html |date=2020-04-06 }}</ref>
Rainwater may also be used for [[groundwater recharge]], where the runoff on the ground is collected and allowed to be absorbed, adding to the [[groundwater]]. In US, rooftop rainwater is collected and stored in sump.<ref>[http://www.rwh.in/ Rainwater Harvesting and Water Purification System.]</ref>
In India this includes [[Bawdi]]s and [[johad]]s, or ponds which collect the run-off from small streams in wide area.<ref>The River maker, New Scientist, 7 September 2002. [http://www.newscientist.com/article/mg17523595.600.html Online edition] (full article by subscription)</ref><ref>[http://www.infinityfoundation.com/hooja_book.htm Rima Hooja: "Channeling Nature: Hydraulics, Traditional Knowledge Systems, And Water Resource Management in India – A Historical Perspective"]</ref>
<!-- Need a better, more detailed source. -->
<!--Recharging the groundwater in this way is claimed to not only improve the year-round availability of groundwater, but also lead to more richer vegetation. (I was going to add this and realized I don't know if it's a direct effect of higher water tables, or if they're using the groundwater to irrigate, thus causing the greening. --Singkong2005 -->


=== Supplemental in drought ===
In India, reservoirs called [[tanka]]s were used to store water; typically they were shallow with mud walls. Ancient tankas still exist in some places.<ref>[http://www.infinityfoundation.com/hooja_book.htm Rima Hooja: "Channeling Nature: Hydraulics, Traditional Knowledge Systems, And Water Resource Management in India – A Historical Perspective"]</ref>
When drought occurs, rainwater harvested in past months can be used. If rain is scarce but also unpredictable, the use of a rainwater harvesting system can be critical to capturing the rain when it does fall. Many countries with arid environments, use rainwater harvesting as a cheap and reliable source of clean water. To enhance irrigation in arid environments, ridges of soil are constructed to trap and prevent rainwater from running downhills. Even in periods of low [[rainfall]], enough water is collected for crops to grow. Water can be collected from roofs and tanks can be constructed to hold large quantities of rainwater.


In addition, rainwater harvesting decreases the demand for water from wells, enabling groundwater levels to be further sustained rather than depleted.
==Quality==
As rainwater may be contaminated, it is often not considered suitable for drinking without [[water purification|treatment]]. However, there are many examples of rainwater being used for all purposes — including drinking — following suitable treatment.


=== Life-cycle assessment ===
Rainwater harvested from roofs can contain animal and bird [[feces]], [[moss]]es and [[lichen]]s, windblown dust, particulates from urban [[pollution]], pesticides, and inorganic [[ion]]s from the sea ([[Calcium|Ca]], [[Magnesium|Mg]], [[Sodium|Na]], [[Potassium|K]], [[Chlorine|Cl]], [[sulfate|SO<sub>4</sub>]]), and dissolved gases ([[carbon dioxide|CO<sub>2</sub>]], [[nitrogen oxide|NO<sub>x</sub>]], [[sulfur oxide|SO<sub>x</sub>]]). High levels of pesticide have been found in rainwater in Europe the highest concentrations occurring in the first rain immediately after a dry spell;<ref>[http://www.greenspun.com/bboard/q-and-a-fetch-msg.tcl?msg_id=000fya It's raining pesticides], ''New Scientist'', 3 April 1999.</ref> the concentration of these and other contaminants are reduced significantly by diverting the initial flow of water to waste, as described above. The water may need to be analysed properly, and used in a way appropriate to its safety. In Gansu province, for example, harvested rainwater is boiled in parabolic solar cookers before being used for drinking.{{Fact|date=February 2007}} In Brazil [[alum]] and [[chlorine]] is added to disinfect water before consumption.{{Fact|date=February 2007}}<!--For rainwater? --Singkong2005 --> [[Appropriate technology]] methods such as [[solar water disinfection]], provide low-cost disinfection options for treatment of stored rainwater for drinking.
[[Life-cycle assessment]] is a methodology used to evaluate the environmental impacts of a system from cradle-to-grave of its lifetime. Devkota et al,<ref>{{Cite journal |last1=Devkota |first1=J. |last2=Schlachter |first2=H. |last3=Anand |first3=C. |last4=Phillips |first4=R. |last5=Apul |first5=Defne |date=November 2013 |title=Development and application of EEAST: A lifecycle-based model for use of harvested rainwater and composting toilets in buildings |journal=Journal of Environmental Management |volume=130 |pages=397–404 |doi=10.1016/j.jenvman.2013.09.015|pmid=24141064 |bibcode=2013JEnvM.130..397D }}</ref><ref name="Devkota 20152">{{Cite journal |last1=Devkota |first1=Jay |last2=Schlachter |first2=Hannah |last3=Apul |first3=Defne |date=May 2015 |title=Life cycle based evaluation of harvested rainwater use in toilets and for irrigation |journal=Journal of Cleaner Production |volume=95 |pages=311–321 |doi=10.1016/j.jclepro.2015.02.021|bibcode=2015JCPro..95..311D }}</ref> developed such a methodology for rainwater harvesting, and found that the building design (e.g., dimensions) and function (e.g., educational, residential, etc.) play critical roles in the environmental performance of the system.


To address the functional parameters of rainwater harvesting systems, a new metric was developed – the demand to supply ratio (D/S) – identifying the ideal building design (supply) and function (demand) in regard to the environmental performance of rainwater harvesting for toilet flushing. With the idea that supply of rainwater not only saves the potable water but also saves the stormwater entering the combined sewer network (thereby requiring treatment), the savings in environmental emissions were higher if the buildings are connected to a combined sewer network compared to separate one.<ref name="Devkota 20152" />
==References==

=== Cost-effectiveness ===
Although standard RWH systems can provide a water source to developing regions facing poverty, the average cost for an RWH setup can be costly depending on the type of technology used. Governmental aid and NGOs can assist communities facing poverty by providing the materials and education necessary to develop and maintain RWH setups.<ref name="Cain-2014">{{Cite journal|last=Cain|first=Nicholas L.|date=2014|title=A Different Path: The Global Water Crisis and Rainwater Harvesting|url=https://www.jstor.org/stable/26476158|journal=Consilience|issue=12|pages=147–157|jstor=26476158|issn=1948-3074|access-date=2020-11-26|archive-date=2021-08-10|archive-url=https://web.archive.org/web/20210810153651/https://www.jstor.org/stable/26476158|url-status=live}}</ref>

Some studies show that rainwater harvesting is a widely applicable solution for water scarcity and other multiple usages, owing to its cost-effectiveness and eco-friendliness.<ref name="Cain-2014" /><ref>{{cite journal |last1=Staddon |first1=Chad |last2=Rogers |first2=Josh |last3=Warriner |first3=Calum |last4=Ward |first4=Sarah |last5=Powell |first5=Wayne |title=Why doesn't every family practice rainwater harvesting? Factors that affect the decision to adopt rainwater harvesting as a household water security strategy in central Uganda |journal=Water International |date=17 November 2018 |volume=43 |issue=8 |pages=1114–1135 |doi=10.1080/02508060.2018.1535417|s2cid=158857347 |doi-access=free |bibcode=2018WatIn..43.1114S }}</ref> Constructing new substantial, centralized water supply systems, such as dams, is prone to damage local ecosystems, generates external social costs, and has limited usages, especially in developing countries or impoverished communities. On the other hand, installing rainwater harvesting systems is verified by a number of studies to provide local communities a sustainable water source, accompanied by other various benefits, including protection from flood and control of water runoff, even in poor regions.<ref name="Cain-2014" /><ref>{{Cite book|last=Furumai|first=Hiroaki|title=Recent application of rainwater storage and harvesting in Japan|year=2008}}</ref> Rainwater harvesting systems that do not require major construction or periodic maintenance by a professional from outside the community are more friendly to the environment and more likely to benefit the local people for a longer period of time.<ref name="Cain-2014" /> Thus, rainwater harvesting systems that could be installed and maintained by local people have bigger chances to be accepted and used by more people.

The usage of [[In situ|in-situ]] technologies can reduce investment costs in rainwater harvesting. In-situ technologies for rainwater harvesting could be a feasible option for [[Rural area|rural areas]] since less material is required to construct them. They can provide a reliable water source that can be utilized to expand agricultural outputs. Above-ground tanks can collect water for [[Domestic technology|domestic use]]; however, such units can be unaffordable to people in poverty.<ref>{{Cite web|last=Lunduka|first=Rodney|date=2011|title=ECONOMIC ANALYSIS OF RAINWATER HARVESTING AND SMALL-SCALE WATER RESOURCES DEVELOPMENT|url=https://www.researchgate.net/publication/316284488|access-date=2020-11-25|website=ResearchGate}}</ref>

== Limitations ==

Rainwater harvesting is a widely used method of storing rainwater in countries presenting with drought characteristics. Several pieces of research have derived and developed different criteria and techniques to select suitable sites for harvesting rainwater. Some research was identified and selected suitable sites for the potential erection of dams, as well as derived a model builder in ArcMap 10.4.1. The model combined several parameters, such as slope, runoff potential, land cover/use, stream order, [[soil quality]], and hydrology to determine the suitability of the site for harvesting rainwater.<ref>{{Cite journal|last1=Ibrahim|first1=Gaylan Rasul Faqe|last2=Rasul|first2=Azad|last3=Ali Hamid|first3=Arieann|last4=Ali|first4=Zana Fattah|last5=Dewana|first5=Amanj Ahmad|date=April 2019|title=Suitable Site Selection for Rainwater Harvesting and Storage Case Study Using Dohuk Governorate|journal=Water|language=en|volume=11|issue=4|pages=864|doi=10.3390/w11040864|doi-access=free}} [[File:CC-BY icon.svg|50px]] Text was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License] {{Webarchive|url=https://web.archive.org/web/20171016050101/https://creativecommons.org/licenses/by/4.0/ |date=2017-10-16 }}.</ref>

Harvested water from RWH systems can be minimal during below-average precipitation in [[Desert climate|arid]] urban regions such as the [[Middle East]]. RWH is useful for developing areas as it collects water for [[irrigation]] and domestic purposes. However, the gathered water should be adequately [[Filtration|filtered]] to ensure safe drinking.<ref>{{Cite journal|last1=Lange|first1=J.|last2=Husary|first2=S.|last3=Gunkel|first3=A.|last4=Bastian|first4=D.|last5=Grodek|first5=T.|date=2012-03-06|title=Potentials and limits of urban rainwater harvesting in the Middle East|url=https://hess.copernicus.org/articles/16/715/2012/|journal=Hydrology and Earth System Sciences|language=en|volume=16|issue=3|pages=715–724|doi=10.5194/hess-16-715-2012|bibcode=2012HESS...16..715L|issn=1607-7938|doi-access=free|access-date=2020-11-28|archive-date=2022-07-10|archive-url=https://web.archive.org/web/20220710023556/https://hess.copernicus.org/articles/16/715/2012/|url-status=live}}</ref>

=== Quality of water ===
Rainwater may need to be analyzed properly, and used in a way appropriate to its safety. In the [[Gansu]] province, for example, [[solar water disinfection]] is used by boiling harvested rainwater in parabolic solar cookers before being used for drinking.<ref>{{Cite news |url=http://english.people.com.cn/90001/90781/6248934.html |last=Chen |first=Xuefei |title=Rainwater harvesting benefits farmers in Gansu |work=People's Daily Online |date=27 August 2007 |access-date=10 July 2018 |archive-date=20 October 2012 |archive-url=https://web.archive.org/web/20121020003759/http://english.people.com.cn/90001/90781/6248934.html |url-status=live }}</ref> These so-called "[[appropriate technology]]" methods provide low-cost disinfection options for treatment of stored rainwater for drinking.

While rainwater itself is a clean source of water, often better than groundwater or water from rivers or lakes,<ref>{{cite web |last1=Hatch |first1=Jacob |title=The Many Benefits of Rainwater Harvesting |url=https://hydrationanywhere.com/the-many-benefits-of-rain-water-harvesting/ |website=Hydration Anywhere |access-date=3 August 2018 |archive-date=13 December 2016 |archive-url=https://web.archive.org/web/20161213021007/https://hydrationanywhere.com/the-many-benefits-of-rain-water-harvesting/ |url-status=dead }}</ref> the process of collection and storage often leaves the water polluted and non-potable. Rainwater harvested from roofs can contain human, animal and bird [[feces]], [[Moss|mosses]] and [[Lichen|lichens]], windblown dust, particulates from urban pollution, pesticides, and inorganic [[Ion|ions]] from the sea ([[Calcium|Ca]], [[Magnesium|Mg]], [[Sodium|Na]], [[Potassium|K]], [[Chlorine|Cl]], [[Sulfate|SO4]]), and dissolved gases ([[Carbon dioxide|CO<sub>2</sub>]], [[Nitrogen oxide|NO<sub>x</sub>]], [[Sulfur oxide|SO<sub>x</sub>]]). High levels of pesticide have been found in rainwater in Europe with the highest concentrations occurring in the first rain immediately after a dry spell;<ref name="Pearce-1999">{{Cite magazine|last1=Pearce|first1=Fred|last2=Mackenzie|first2=Debora|date=3 April 1999|title=It's raining pesticides|url=https://www.newscientist.com/article/mg16221803-100-its-raining-pesticides/|magazine=New Scientist|issue=2180|access-date=10 July 2018|archive-date=10 July 2018|archive-url=https://web.archive.org/web/20180710102528/https://www.newscientist.com/article/mg16221803-100-its-raining-pesticides/|url-status=live}}</ref> the concentration of these and other contaminants are reduced significantly by diverting the [[First flush|initial flow]] of run-off water to waste. Improved water quality can also be obtained by using a floating draw-off mechanism (rather than from the base of the tank) and by using a series of tanks, withdraw from the last in series. Prefiltration is a common practice used in the industry to keep the system healthy and ensure that the water entering the tank is free of large sediments.

A concept of rainwater harvesting and cleaning it with solar energy for rural household drinking purposes has been developed by [[Nimbkar Agricultural Research Institute]].<ref name="Patange-2020">{{Cite web |url=https://www.currentscience.ac.in/Volumes/118/06/0872.pdf |title=Low cost drinking water technology – rainwater harvesting with solar purification. Current Science, Vol. 118, No.6, 25 March 2020 |access-date=27 March 2020 |archive-date=19 January 2022 |archive-url=https://web.archive.org/web/20220119182928/https://www.currentscience.ac.in/Volumes/118/06/0872.pdf |url-status=live }}</ref>

Conceptually, a water supply system should match the quality of water with the end-user. However, in most of the developed world, high-quality potable water is used for all end uses. This approach wastes money and energy and imposes unnecessary impacts on the environment. Supplying rainwater that has gone through preliminary filtration measures for non-potable water uses, such as toilet flushing, irrigation, and laundry, may be a significant part of a sustainable water management strategy.

Rainwater cisterns can also act as habitat for pathogen-bearing mosquitoes. As a result, care must be taken to ensure that female mosquitoes can not access the cistern to lay eggs. Larvae eating fish can also be added to the cistern, or it can be chemically treated.

== Country examples ==
=== Canada ===
{{Excerpt|Rainwater harvesting in Canada|paragraphs=1,2}}

=== India ===
{{excerpt|Water supply and sanitation in India#Rainwater harvesting|paragraphs=1|file=0}}While rainwater harvesting in an urban context has gained traction in recent years, evidence points toward [[Water supply and sanitation in India#Rainwater harvesting|rainwater harvesting in rural India]] since ancient times.

=== United Kingdom ===
{{Excerpt|Rainwater harvesting in the United Kingdom|paragraphs=1,2}}

=== United States ===
{{Excerpt|Water supply and sanitation in the United States#Rainwater harvesting|paragraphs=1,2}}

=== Other countries ===
[[File: Rainwater harvesting tank (5981896147).jpg|thumb|Rainwater harvesting tank in [[Rwanda]].]]
* [[Uganda]]: Rainwater harvesting has been used in Uganda to promote household and community scale water security for many years. Regular maintenance is an ongoing challenge with existing installation and there are many examples of installations that have failed due to poor maintenance. Research has also shown that awareness of RWH and how to access necessary resources to implement RWH is variable across Ugandan society.<ref name="Staddon-2018" />
* [[Thailand]] has the largest fraction of the population in the rural area relying on rainwater harvesting (currently around 40%).<ref name="JMP 2016">{{Cite web|last=JMP|date=2016|title=Joint Monitoring Programme Thailand Data|url=https://www.wssinfo.org/fileadmin/user_upload/resources/Thailand.xls/|access-date=2017-03-13}}{{Dead link|date=March 2021|bot=InternetArchiveBot|fix-attempted=yes}}</ref> Rainwater harvesting was promoted heavily by the government in the 1980s. In the 1990s, after government funding for the collection tanks ran out, the private sector stepped in and provided several million tanks to private households, many of which continue to be used.<ref name="saladin20162">{{Cite web|last=Saladin|first=Matthias|date=2016|title=Rainwater Harvesting in Thailand - learning from the World Champions|url=http://rural-water-supply.net/en/resources/details/759|access-date=2017-03-13|archive-date=2019-01-29|archive-url=https://web.archive.org/web/20190129200110/http://www.rural-water-supply.net/en/resources/details/759|url-status=live}}</ref> This is one of the largest examples of [[Self-supply of water and sanitation|self-supply of water]] worldwide.
*In [[Bermuda]], the law requires all new construction to include rainwater harvesting adequate for the residents.<ref>{{cite news|author=Harry Low|date=December 23, 2016|title=Why houses in Bermuda have white stepped roofs|work=BBC News|url=https://www.bbc.co.uk/news/magazine-38222271|access-date=2016-12-23|archive-date=2016-12-23|archive-url=https://web.archive.org/web/20161223024443/http://www.bbc.co.uk/news/magazine-38222271|url-status=live}}</ref>
*[[New Zealand]] has plentiful rainfall in the West and South, and rainwater harvesting is the normal practice in many rural areas, using roof water directed by [[rain gutter |spouting]] into covered, 1000 litre storage tanks, with the encouragement of most local councils.<ref>{{Cite web|date=28 April 2016|title=Rainwater tanks|url=http://www.gw.govt.nz/rainwater-tanks//|url-status=dead|archive-url=https://web.archive.org/web/20160414164122/http://www.gw.govt.nz/rainwater-tanks//|archive-date=14 April 2016|access-date=21 March 2017|publisher=Greater Wellington Regional Council}}</ref>
* In [[Sri Lanka]], rainwater harvesting has been a popular method of obtaining water for agriculture and for drinking purposes in rural homes. The legislation to promote rainwater harvesting was enacted through the Urban Development Authority (Amendment) Act, No. 36 of 2007.<ref>{{Cite web|title=Parliament Of The Democratic Socialist Republic of Sri Lanka|url=http://www.lankarainwater.org/rwhsl/act_36_2007_e.pdf|access-date=2011-12-09|archive-date=2013-11-04|archive-url=https://web.archive.org/web/20131104180251/http://www.lankarainwater.org/rwhsl/act_36_2007_e.pdf|url-status=dead}}</ref> The Lanka Rainwater Harvesting Forum is leading Sri Lanka's initiative.<ref>{{Cite web|title=Lanka Rain Water Harvesting Forum (LRWHF)|url=http://www.lankarainwater.org/|access-date=2011-12-09|archive-date=2015-02-03|archive-url=https://web.archive.org/web/20150203171925/http://www.lankarainwater.org/|url-status=live}}</ref> The [[tank cascade system]] is an ancient irrigation system spanning the island of Sri Lanka.

== History ==
{{See also|History of water supply and sanitation}}
The construction and use of [[cistern]]s to store rainwater can be traced back to the [[Neolithic Age]], when waterproof lime plaster cisterns were built in the floors of houses in village locations of the [[Levant]], a large area in Southwest Asia, south of the [[Taurus Mountains]], bounded by the [[Mediterranean Sea]] in the west, the [[Arabian Desert]] in the south, and [[Mesopotamia]] in the east. By the late 4000 BC{{clarify|date=June 2023}}, cisterns were essential elements of emerging water management techniques used in [[dry-land farming]].<ref name="Mays et al. 2013">{{cite journal|last1=Mays|first1=Larry|last2=Antoniou|first2=George|last3=Angelakis|first3=Andreas|date=2013|title=History of water cisterns: Legacies and lessons|journal=Water|volume=5|issue=4|pages=1916–1940|doi=10.3390/w5041916|name-list-style=amp|doi-access=free|hdl=2286/R.I.43114|hdl-access=free}}</ref>

Many ancient cisterns have been discovered in some parts of [[Jerusalem]] and throughout what is today Israel/Palestine. At the site believed by some to be that of the biblical city of Ai (Khirbet et-Tell), a large cistern dating back to around 2500 BC was discovered that had a capacity of nearly {{Convert|1,700|m3|cuft|abbr=on}}. It was carved out of a solid rock, lined with large stones, and sealed with clay to keep it from leaking.<ref name="Mays et al. 2013" />

The Greek island of [[Crete]] is also known for its use of large cisterns for rainwater collection and storage during the [[Minoan civilization|Minoan]] period from 2,600 BC–1,100 BC. Four large cisterns have been discovered at [[Myrtos Pyrgos|Myrtos-Pyrgos]], [[Archanes]], and Zakroeach. The cistern found at Myrtos-Pyrgos was found to have a capacity of more than {{Convert|80|m3|cuft|abbr=on}} and to date back to 1700 BC.<ref name="Mays et al. 2013" />

Around 300 BC, farming communities in [[Balochistan]] (now located in Pakistan, Afghanistan, and Iran), and [[Kutch]], India, used rainwater harvesting for agriculture and many other uses.<ref>{{Cite web|title=Rain water Harvesting|url=http://www.tn.gov.in/dtp/rainwater.htm|access-date=23 January 2012|publisher=Tamil Nadu State Government, India|archive-date=12 August 2019|archive-url=https://web.archive.org/web/20190812001933/http://www.tn.gov.in/dtp/rainwater.htm|url-status=live}}</ref> Rainwater harvesting was done by [[Chola dynasty|Chola kings]] as well.<ref>{{Cite news|date=17 July 2010|title=Believes in past, lives in future|newspaper=[[The Hindu]]|location=India|url=http://www.hindu.com/mp/2010/07/17/stories/2010071754460800.htm|archive-url=https://web.archive.org/web/20121009054927/http://www.hindu.com/mp/2010/07/17/stories/2010071754460800.htm|url-status=dead|archive-date=9 October 2012}}</ref> Rainwater from the [[Brihadeeswarar temple]] (located in Balaganapathy Nagar, [[Thanjavur]], India) was collected in Shivaganga tank.<ref>{{Cite news|date=24 August 2003|title=Rare Chola inscription found near Big Temple|location=India|url=http://www.hindu.com/2003/08/04/stories/2003080402510500.htm|archive-url=https://web.archive.org/web/20031122132516/http://www.hindu.com/2003/08/04/stories/2003080402510500.htm|url-status=dead|newspaper=[[The Hindu]]|archive-date=22 November 2003}}</ref> During the later Chola period, the Vīrānam tank was built (1011 to 1037 AD) in the Cuddalore district of [[Tamil Nadu]] to store water for drinking and irrigation purposes. Vīrānam is a 16-km-long tank with a storage capacity of {{Convert|1,465,000,000|cuft|m3|abbr=on}}.

Rainwater harvesting was also common in the [[Roman Empire]].<ref>{{cite book|last1=Kamash|first1=Zena|title=Archaeologies of Water in the Roman Near East|date=2010|publisher=Gorgias Press}}</ref> While [[Roman aqueduct]]s are well-known, [[List of Roman cisterns|Roman cisterns]] were also commonly used and their construction expanded with the Empire.<ref name="Mays et al. 2013" /> For example, in [[Pompeii]], rooftop water storage was common before the construction of [[Aqua Augusta (Naples)|the aqueduct]] in the 1st century BC.<ref name="ArchServe-2016">{{Cite web|title=Water Supply Systems: Cisterns, Reservoirs, Aqueducts {{!}} Roman Building Technology and Architecture, University of California Santa Barbara|url=https://archserve.id.ucsb.edu/courses/arthistory/152k/water.html|access-date=2018-04-13|website=ArchServe|archive-date=2016-07-18|archive-url=https://web.archive.org/web/20160718072245/http://archserve.id.ucsb.edu/courses/arthistory/152k/water.html|url-status=live}}</ref> This history continued with the Byzantine Empire; for example, the [[Basilica Cistern]] in Istanbul.

Though little known, the town of [[Venice]] for centuries depended on rainwater harvesting. The lagoon surrounding Venice is brackish water, which is unsuitable for drinking. Venice's ancient inhabitants established a rainwater collection system based on man-made insulated collection wells.<ref>{{cite web|title=Venetian wells|url=http://www.venicebackstage.org/en/159/i-pozzi-veneziani|access-date=2016-08-29|archive-date=2019-05-09|archive-url=https://web.archive.org/web/20190509005248/http://www.venicebackstage.org/en/159/i-pozzi-veneziani/|url-status=live}}</ref> Water percolated down the specially designed stone flooring, and was filtered by a layer of sand, then collected at the bottom of the well. Later, as Venice acquired territories on the mainland, it started to import water by boat from local rivers. Still, the wells remained in use and were especially important in times of war when an enemy could block access to the mainland water.

== See also ==
{{Portal|Ecology}}
{{div col}}
* {{annotated link|Air well (condenser)}}
* {{annotated link|Atmospheric water generator}}
* {{annotated link|Blue roof}}
* {{annotated link|Catchwater}}
* {{annotated link|Desalination}}
* {{annotated link|Detention basin}}
* {{annotated link|Dew pond}}
* {{annotated link|Hydropower}}
* {{annotated link|Peak water}}
* {{annotated link|Rain power}}
* {{annotated link|Rainwater harvesting in the Sahel}}
* {{annotated link|Retention basin}}
* {{annotated link|Sponge city}}
* {{annotated link|Tank cascade system}}
* {{annotated link|Water conservation}}
{{div col end}}

== References ==
{{Reflist}}
{{Reflist}}


== External links ==
==Bibliography==
*Frasier, Gary, and Lloyd Myers. Handbook of Water Harvesting. Washington D.C.: U.S. Dept. of Agriculture, Agricultural Research Service, 1983
*Gould, John, and Erik Nissen-Peterson. Rainwater Catchment Systems. UK: Intermediate Technology Publications, 1999.
*Hemenway, Toby. Gaia’s Garden: A Guide to Home-Scale Permaculture. Vermont: Chelsea Green Publishing Company, 2000.
*{{cite book | first = P. | last = Lowes | year = 1987 | title = Developing World Water | chapter = The Water Decade: Half Time | editor = in John Pickford (ed.) | pages = pp 16-17 | publisher = Grosvenor Press International | location = London | id = ISBN 0-946027-29-3}}
*Ludwig, Art. Create an Oasis With Greywater: Choosing, Building, and Using Greywater Systems. California: Oasis Design, 1994.
*Pacey, Arnold, and Adrian Cullis. Rainwater Harvesting. UK: Intermediate Technology Publications, 1986.


{{Sister project links | wikt=no | n=no | q=no | s=no |v=no}}
==External links==
{{Wikiversity}}
{{External links|July 2007}}
{{Wikibooks}}
*[http://www.rwh.in Rainwater Harvesting and Purification System] - A case study is given to understand the basic process of collection and use of rainwater.
*[http://groups.yahoo.com/group/rainwaterharvesting/ Rainwater Harvesting Forum] - This is a free and open forum for discussion of rainwater harvesting as alternative source of water for household, garden and rainfed farming needs.
*[http://www.rwhdigest.com rwhdigest.com] – Online digest promoting sustainable water management practices. Includes articles, case studies, discussion forum and instructions for establishing collection systems.
*[http://www.harvestingrainwater.com/ Rainwater Harvesting for Drylands and Beyond] - Contains resources for rainwater harvesting in the Southwestern United States and beyond.
*[http://www.indiawaterportal.org/tt/rwh/ RWH on India Water Portal] - India Water Portal has a comprehensive section on Rainwater Harvesting which includes case studies, courses, movies and policies.
*[http://www.appropedia.org/Original:Rainwater_harvesting Rainwater harvesting System set-up information from Appropedia].
*[http://www.mywaterwisehome.com Mywaterwisehome.com] - Water sensitive design in a private Australian home. Builder is a PhD candidate researching household decision making to adopt decentralised pro-environmental technologies.
*[http://www.watercache.com Innovative Water Solutions, LLC] - A residential and commercial rainwater harvesting system design/installation firm located in Austin, Texas.
*[http://www.rainwaterglossary.com The rainwater glossary]Information about and pictures of the components used in building a rainwater harvesting system - Australian content
*[http://www.jrsmith.com/products/rainwater_harvesting/resources.htm Rainwater Harvesting Resources] Case Studies, Articles, Presentations, Webinars and Videos of Rainwater Harvesting Technologies, Applications, Products and Solutions
*[http://www.oasisdesign.net/water/index.htm Water Storage]: information about water Storage and other ecological systems for water supply, including rainwater harvesting
*[http://akash-ganga-rwh.com/RWH/WaterHarvesting.html Akash Ganga RWH] - A starter site for India-centric RWH information.
*[http://www.harvesth2o.com Harvesth2o.com] – online rainwater harvesting community.
*[http://www.riversides.org/rainguide/index.php Homeowner's guide to rainfall] Instructional website for urban home-based rainwater harvesting.
*[http://www.irha-h2o.org International Rainwater Harvesting Alliance (IRHA)] International alliance created at the Johannesburg World Summit on sustainable development.
*[http://www.ircsa.org International Rainwater Catchment Association (IRCSA)] International organization on rainwater harvesting.
*[http://www.kediarainwater.org Kedia R.W.H. Pattern] – innovative methods and success stories
*[http://www.rainwatermanagement.com Rainwater Management Solutions - Engineered Turnkey solutions for rainwater harvesting and stormwater management]
*[http://www.rainwaterclub.org Rainwater harvesting in India]
*[http://texaswater.tamu.edu/conservation.rainwater.html Rainwater Harvesting] at Texas A&M University Extension
*[http://crs.org/publications/pdf/Wat0804_e.pdf] - CRS Ferrocement Water Tank Construction Manual.
*[http://www.rainwate.rharvesting.org/ Rainwaterharvesting.org] - Making water everybody's business.
*[[Appropedia:Rainwater]] - articles and project descriptions on Appropedia, the sustainability wiki, for project and how-to content.
*[http://www.arid.asn.au Australian Rainwater Industry Development group] - an association for the promotion and development of innovation in rainwater harvesting.
*[http://rainfoundation.org/ RAINfoundation.org] '''R'''ainwater '''H'''arvesting '''I'''mplementation '''N'''etwork : focuses on field implementation of small-scale rainwater harvesting projects
*[http://www.lakotawatercompany.com/joomla/content/view/16/28/ Lakota Water Company - How Rainwater Collection Works] - A simple graphical representation of how a rainwater collection system works.
*[http://www.ppltraining.co.uk/courses/bpec-rainwater-harvesting-course-21.htm Rainwater Training in UK] Rainwater Harvesting Training in the UK


[[Category:Rainwater harvesting| ]]
[[Category:Water supply]]
[[Category:Water supply]]
[[Category:Water conservation]]
[[Category:Water conservation]]
[[Category:Irrigation]]
[[Category:Irrigation]]
[[Category:Appropriate technology]]
[[Category:Appropriate technology]]
[[Category:Hydrology and urban planning]]
[[Category:Sustainable gardening]]
[[Category:DIY culture]]
[[Category:DIY culture]]

[[de:Rainwater Harvesting]]
[[es:Cisterna]]
[[fr:Eau pluviale]]
[[ml:മഴവെള്ള സംഭരണം]]
[[pt:Cisterna]]
[[ta:மழை நீர் சேகரம்]]

Latest revision as of 14:06, 15 December 2024

configuration of domestic rainwater harvesting system in Uganda.[1]

Rainwater harvesting (RWH) is the collection and storage of rain, rather than allowing it to run off. Rainwater is collected from a roof-like surface and redirected to a tank, cistern, deep pit (well, shaft, or borehole), aquifer, or a reservoir with percolation, so that it seeps down and restores the ground water. Rainwater harvesting differs from stormwater harvesting as the runoff is typically collected from roofs and other area surfaces for storage and subsequent reuse.[2]: 10  Its uses include watering gardens, livestock,[3] irrigation, domestic use with proper treatment, and domestic heating. The harvested water can also be used for long-term storage or groundwater recharge.[4]

Rainwater harvesting is one of the simplest and oldest methods of self-supply of water for households, having been used in South Asia and other countries for many thousands of years.[5] Installations can be designed for different scales, including households, neighborhoods, and communities, and can also serve institutions such as schools, hospitals, and other public facilities.[6]

Uses

[edit]
Rainwater capture and storage system, Mexico City campus, Monterrey Institute of Technology and Higher Education
Cistern, Mission District, San Francisco, California
Rainwater capture, Gibraltar East Side, 1992
Home, with rain collection jars on roof, Panarea, Aeolian Islands, north of Sicily, Italy[7]
Rainwater harvesting and hand washing system for a toilet in Kenya.
Rainwater harvesting in Burkina Faso
Plastic Pond for Rainwater Harvesting, Nepal, 2013[8]
Rainwater harvesting system, Kiribati

Domestic use

[edit]

Rooftop rainwater harvesting is used to provide drinking water, domestic water, water for livestock, water for small irrigation, and a way to replenish groundwater levels.

Kenya has already been successfully harvesting rainwater for toilets, laundry, and irrigation. Since the establishment of the 2016 Water Act, Kenya has prioritized regulating its agriculture industry.[9] Additionally, areas in Australia use harvested rainwater for cooking and drinking.[10] Studies by Stout et al. on the feasibility of RWH in India found it most beneficial for small-scale irrigation, which provides income from produce sales, and for groundwater recharge.[10]

Agriculture

[edit]

In regards to urban agriculture, rainwater harvesting in urban areas reduces the impact of runoff and flooding. The combination of urban 'green' rooftops with rainwater catchments have been found to reduce building temperatures by more than 1.3 degrees Celsius. Rainwater harvesting in conjunction with urban agriculture would be a viable way to help meet the United Nations Sustainable Development Goals for cleaner and sustainable cities, health and wellbeing, and food and water security (Sustainable Development Goal 6). The technology is available, however, it needs to be remodeled in order to use water more efficiently, especially in an urban setting.

Missions to five Caribbean countries have shown that the capture and storage of rainwater runoff for later use is able to significantly reduce the risk of losing some or all of the year's harvest because of soil or water scarcity. In addition, the risks associated with flooding and soil erosion during high rainfall seasons would decrease. Small farmers, especially those farming on hillsides, could benefit the most from rainwater harvesting because they are able to capture runoff and decrease the effects of soil erosion.[11]

Many countries, especially those with arid environments, use rainwater harvesting as a cheap and reliable source of clean water.[12] To enhance irrigation in arid environments, ridges of soil are constructed to trap and prevent rainwater from running down hills and slopes. Even in periods of low rainfall, enough water is collected for crops to grow.[13] Water can be collected from roofs, dams and ponds can be constructed to hold large quantities of rainwater so that even on days when little to no rainfall occurs, enough is available to irrigate crops.

Industry

[edit]

Frankfurt Airport has the largest rainwater harvesting system in Germany, saving approximately 1 million cubic meters of water per year. The cost of the system was 1.5 million dm (US$63,000) in 1993. This system collects water from the roofs of the new terminal which has an area of 26,800 square meters. The water is collected in the basement of the airport in six tanks with a storage capacity of 100 cubic meters. The water is mainly used for toilet flushing, watering plants and cleaning the air conditioning system.[14]

Rainwater harvesting was adopted at The Velodrome – The London Olympic Park – in order to increase the sustainability of the facility. A 73% decrease in potable water demand by the park was estimated. Despite this, it was deemed that rainwater harvesting was a less efficient use of financial resources to increase sustainability than the park's blackwater recycling program.[15]

Technologies

[edit]

Traditionally, stormwater management using detention basins served a single purpose. However, optimized real-time control lets this infrastructure double as a source of rainwater harvesting without compromising the existing detention capacity.[16] This has been used in the EPA headquarters to evacuate stored water prior to storm events, thus reducing wet weather flow while ensuring water availability for later reuse. This has the benefit of increasing water quality released and decreasing the volume of water released during combined sewer overflow events.[17][18]

Generally, check dams are constructed across the streams to enhance the percolation of surface water into the subsoil strata. The water percolation in the water-impounded area of the check dams can be enhanced artificially manyfold by loosening the subsoil strata and ANFO explosives as used in open cast mining. Thus, local aquifers can be recharged quickly using the available surface water fully for use in the dry season.

System setup

[edit]

Rainwater harvesting systems can range in complexity, from systems that can be installed with minimal skills, to automated systems that require advanced setup and installation. The basic rainwater harvesting system is more of a plumbing job than a technical job, as all the outlets from the building's terrace are connected through a pipe to an underground tank that stores water. There are common components that are installed in such systems, such as pre-filters (see e.g. vortex filter), drains/gutters, storage containers, and depending on whether the system is pressurized, also pumps, and treatment devices such as UV lights, chlorination devices and post-filtration equipment.

Systems are ideally sized to meet the water demand throughout the dry season since it must be big enough to support daily water consumption. Specifically, the rainfall capturing area such as a building roof must be large enough to maintain an adequate flow of water. The water storage tank size should be large enough to contain the captured water. For low-tech systems, many low-tech methods are used to capture rainwater: rooftop systems, surface water capture, and pumping the rainwater that has already soaked into the ground or captured in reservoirs and storing it in tanks (cisterns).

Rainwater harvesting by solar power panels

[edit]

Good quality water resources near populated areas are becoming scarce and costly for consumers. In addition to solar and wind energy, rainwater is a major renewable resource for any land. Vast areas are being covered by solar PV panels every year in all parts of the world. Solar panels can also be used for harvesting most of the rainwater falling on them and drinking quality water, free from bacteria and suspended matter, can be generated by simple filtration and disinfection processes as rainwater is very low in salinity.[19][20][21] Exploiting rainwater for value-added products like bottled drinking water makes solar PV power plants profitable even in high rainfall or cloudy areas by generating additional income. Recently, cost-effective rainwater collection in existing wells has been found highly effective in raising groundwater levels in India.

Other innovations

[edit]

The Groasis Waterboxx is an example of low scale technology, in this case to assist planting of trees in arid area. It harvests rainwater and dew.

Advantages

[edit]

Rainwater harvesting provides the independent water supply during regional water restrictions, and in developed countries, it is often used to supplement the main supply. It provides water when a drought occurs, can help mitigate flooding of low-lying areas, and reduces demand on wells which may enable groundwater levels to be sustained. Rainwater harvesting increases the availability of water during dry seasons by increasing the levels of dried borewells and wells. Surface water supply is readily available for various purposes thus reducing dependence on underground water. It improves the quality of ground by diluting salinity. It does not cause pollution and is environmentally friendly. It is cost-effective and easily affordable. It also helps in the availability of potable water, as rainwater is substantially free of salinity and other salts. Applications of rainwater harvesting in urban water system provides a substantial benefit for both water supply and wastewater subsystems by reducing the need for clean water in water distribution systems, less generated stormwater in sewer systems,[22] and a reduction in stormwater runoff polluting freshwater bodies.

A large body of work has focused on the development of life cycle assessment and its costing methodologies to assess the level of environmental impacts and money that can be saved by implementing rainwater harvesting systems.[21]

Independent water supply

[edit]

Rainwater harvesting provides an independent water supply during water restrictions. In areas where clean water is costly, or difficult to come by, rainwater harvesting is a critical source of clean water. In developed countries, rainwater is often harvested to be used as a supplemental source of water rather than the main source, but the harvesting of rainwater can also decrease a household's water costs or overall usage levels. Rainwater is safe to drink if the consumers do additional treatments before drinking. Boiling water helps to kill germs. Adding another supplement to the system such as a first flush diverter is also a common procedure to avoid contaminants of the water.[23]

Supplemental in drought

[edit]

When drought occurs, rainwater harvested in past months can be used. If rain is scarce but also unpredictable, the use of a rainwater harvesting system can be critical to capturing the rain when it does fall. Many countries with arid environments, use rainwater harvesting as a cheap and reliable source of clean water. To enhance irrigation in arid environments, ridges of soil are constructed to trap and prevent rainwater from running downhills. Even in periods of low rainfall, enough water is collected for crops to grow. Water can be collected from roofs and tanks can be constructed to hold large quantities of rainwater.

In addition, rainwater harvesting decreases the demand for water from wells, enabling groundwater levels to be further sustained rather than depleted.

Life-cycle assessment

[edit]

Life-cycle assessment is a methodology used to evaluate the environmental impacts of a system from cradle-to-grave of its lifetime. Devkota et al,[24][25] developed such a methodology for rainwater harvesting, and found that the building design (e.g., dimensions) and function (e.g., educational, residential, etc.) play critical roles in the environmental performance of the system.

To address the functional parameters of rainwater harvesting systems, a new metric was developed – the demand to supply ratio (D/S) – identifying the ideal building design (supply) and function (demand) in regard to the environmental performance of rainwater harvesting for toilet flushing. With the idea that supply of rainwater not only saves the potable water but also saves the stormwater entering the combined sewer network (thereby requiring treatment), the savings in environmental emissions were higher if the buildings are connected to a combined sewer network compared to separate one.[25]

Cost-effectiveness

[edit]

Although standard RWH systems can provide a water source to developing regions facing poverty, the average cost for an RWH setup can be costly depending on the type of technology used. Governmental aid and NGOs can assist communities facing poverty by providing the materials and education necessary to develop and maintain RWH setups.[26]

Some studies show that rainwater harvesting is a widely applicable solution for water scarcity and other multiple usages, owing to its cost-effectiveness and eco-friendliness.[26][27] Constructing new substantial, centralized water supply systems, such as dams, is prone to damage local ecosystems, generates external social costs, and has limited usages, especially in developing countries or impoverished communities. On the other hand, installing rainwater harvesting systems is verified by a number of studies to provide local communities a sustainable water source, accompanied by other various benefits, including protection from flood and control of water runoff, even in poor regions.[26][28] Rainwater harvesting systems that do not require major construction or periodic maintenance by a professional from outside the community are more friendly to the environment and more likely to benefit the local people for a longer period of time.[26] Thus, rainwater harvesting systems that could be installed and maintained by local people have bigger chances to be accepted and used by more people.

The usage of in-situ technologies can reduce investment costs in rainwater harvesting. In-situ technologies for rainwater harvesting could be a feasible option for rural areas since less material is required to construct them. They can provide a reliable water source that can be utilized to expand agricultural outputs. Above-ground tanks can collect water for domestic use; however, such units can be unaffordable to people in poverty.[29]

Limitations

[edit]

Rainwater harvesting is a widely used method of storing rainwater in countries presenting with drought characteristics. Several pieces of research have derived and developed different criteria and techniques to select suitable sites for harvesting rainwater. Some research was identified and selected suitable sites for the potential erection of dams, as well as derived a model builder in ArcMap 10.4.1. The model combined several parameters, such as slope, runoff potential, land cover/use, stream order, soil quality, and hydrology to determine the suitability of the site for harvesting rainwater.[30]

Harvested water from RWH systems can be minimal during below-average precipitation in arid urban regions such as the Middle East. RWH is useful for developing areas as it collects water for irrigation and domestic purposes. However, the gathered water should be adequately filtered to ensure safe drinking.[31]

Quality of water

[edit]

Rainwater may need to be analyzed properly, and used in a way appropriate to its safety. In the Gansu province, for example, solar water disinfection is used by boiling harvested rainwater in parabolic solar cookers before being used for drinking.[32] These so-called "appropriate technology" methods provide low-cost disinfection options for treatment of stored rainwater for drinking.

While rainwater itself is a clean source of water, often better than groundwater or water from rivers or lakes,[33] the process of collection and storage often leaves the water polluted and non-potable. Rainwater harvested from roofs can contain human, animal and bird feces, mosses and lichens, windblown dust, particulates from urban pollution, pesticides, and inorganic ions from the sea (Ca, Mg, Na, K, Cl, SO4), and dissolved gases (CO2, NOx, SOx). High levels of pesticide have been found in rainwater in Europe with the highest concentrations occurring in the first rain immediately after a dry spell;[34] the concentration of these and other contaminants are reduced significantly by diverting the initial flow of run-off water to waste. Improved water quality can also be obtained by using a floating draw-off mechanism (rather than from the base of the tank) and by using a series of tanks, withdraw from the last in series. Prefiltration is a common practice used in the industry to keep the system healthy and ensure that the water entering the tank is free of large sediments.

A concept of rainwater harvesting and cleaning it with solar energy for rural household drinking purposes has been developed by Nimbkar Agricultural Research Institute.[35]

Conceptually, a water supply system should match the quality of water with the end-user. However, in most of the developed world, high-quality potable water is used for all end uses. This approach wastes money and energy and imposes unnecessary impacts on the environment. Supplying rainwater that has gone through preliminary filtration measures for non-potable water uses, such as toilet flushing, irrigation, and laundry, may be a significant part of a sustainable water management strategy.

Rainwater cisterns can also act as habitat for pathogen-bearing mosquitoes. As a result, care must be taken to ensure that female mosquitoes can not access the cistern to lay eggs. Larvae eating fish can also be added to the cistern, or it can be chemically treated.

Country examples

[edit]

Canada

[edit]
A small rainwater harvesting tank in Quebec.

Rainwater harvesting is becoming a procedure that many Canadians are incorporating into their daily lives, although data does not give exact figures for implementation.[36] Rainwater can be used for a number of purposes including stormwater reduction, irrigation, laundry and portable toilets.[37] In addition to low costs, rainwater harvesting is useful for landscape irrigation. Many Canadians have started implementing rainwater harvesting systems for use in stormwater reduction, irrigation, laundry, and lavatory plumbing. Provincial and municipal legislation is in place for regulating the rights and uses for captured rainwater. Substantial reform to Canadian law since the mid-2000s has increased the use of this technology in agricultural, industrial, and residential use, but ambiguity remains amongst legislation in many provinces. Bylaws and local municipal codes often regulate rainwater harvesting.

Multiple organizations and companies have developed in Canada to provide education, technology, and installation for rainwater harvesting. These include the Canadian Association for Rainwater Management (CANARM),[38] Canadian Mortgage and Housing Corporation (CMHC), and CleanFlo Water Technologies.[39] CANARM is an association that prioritizes education, training and spreading awareness for those entering the rainwater harvesting industry.[38]

India

[edit]
In the early 21st century, India began heavily investing in rainwater harvesting infrastructure and policy as an urgent response to water scarcity.[40] In 2001, Tamil Nadu became the first Indian state to make rainwater harvesting compulsory in every building to avoid groundwater depletion. In Rajasthan, rainwater harvesting has traditionally been practiced by the people of the Thar Desert. Increase in rainwater harvesting efforts across the nation have revived ancient water harvesting systems in Rajasthan, such as the chauka system from the Jaipur district. Other large cities like Pune, Mumbai and Bangalore all have varying rules for mandatory rainwater harvesting, especially in new buildings. In 2002, the Municipal Corporation of Greater Mumbai required all new buildings over 1000 square meters to have rainwater harvesting infrastructure.[41] The law was expanded in 2007 to 300 square meters. The goal was to ensure buildings had enough water to last them through non-monsoon seasons. The process included a catchment system, an initial flush, and extensive filtering. As of 2021, the Brihanmumbai Municipal Corporation (BMC) reported 3000 newly constructed or redeveloped buildings with rainwater harvesting infrastructure.[42] However, many residents have complained that the stored water is contaminated, turning saline and brackish. Experts and residents argue that BMC authorities have done little to take implementation seriously, and the actual effectiveness of the rainwater harvesting mandate is unknown.[43]

While rainwater harvesting in an urban context has gained traction in recent years, evidence points toward rainwater harvesting in rural India since ancient times.

United Kingdom

[edit]

Rainwater harvesting in the United Kingdom is a practice of growing importance. Rainwater harvesting in the UK is both a traditional and a reviving technique for collecting water for domestic uses. The water is generally used for non-hygienic purposes like watering gardens, flushing toilets, and washing clothes.[44] In commercial premises like supermarkets it is used for things like toilet flushing where larger tank systems can be used collecting between 1000 and 7500 litres of water. It is claimed that in the South East of England there is less water available per person than in many Mediterranean countries.[citation needed]

Rainwater is almost always collected strictly from the roof, then heavily filtered using either a filter attached to the down pipe, a fine basket filter or for more expensive systems like self-cleaning filters placed in an underground tank.[45] UK homes using some form of rainwater harvesting system can reduce their mains water usage by 50% or more, although a 20%–30% saving is more common.[46] At present (depending on the area in the UK) mains water delivery and equivalent waste water and sewerage processing costs about £2 per cubic metre. Reducing mains-water metered volumes also reduces the sewerage and sewage disposal costs in the same proportion, because water company billing assumes that all water taken into the house is discharged into the sewers.

United States

[edit]
In the United States, until 2009 in Colorado, water rights laws almost completely restricted rainwater harvesting; a property owner who captured rainwater was deemed to be stealing it from those who have the rights to take water from the watershed. Now, residential good owners who meet certain criteria may obtain a permit to install a rooftop precipitation collection system (SB 09-080).[47] Up to 10 large scale pilot studies may also be permitted (HB 09–1129).[48] The main factor in persuading the Colorado Legislature to change the law was a 2007 study that found that in an average year, 97% of the precipitation that fell in Douglas County, in the southern suburbs of Denver, never reached a stream—it was used by plants or evaporated on the ground. Rainwater catchment is mandatory for new dwellings in Santa Fe, New Mexico.[49] Texas offers a sales tax exemption on the purchase of rainwater harvesting equipment. Both Texas[50] and Ohio allow the practice even for potable purposes. Oklahoma passed the Water for 2060 Act in 2012, to promote pilot projects for rainwater and graywater use among other water-saving techniques.[51]

Other countries

[edit]
Rainwater harvesting tank in Rwanda.
  • Uganda: Rainwater harvesting has been used in Uganda to promote household and community scale water security for many years. Regular maintenance is an ongoing challenge with existing installation and there are many examples of installations that have failed due to poor maintenance. Research has also shown that awareness of RWH and how to access necessary resources to implement RWH is variable across Ugandan society.[1]
  • Thailand has the largest fraction of the population in the rural area relying on rainwater harvesting (currently around 40%).[52] Rainwater harvesting was promoted heavily by the government in the 1980s. In the 1990s, after government funding for the collection tanks ran out, the private sector stepped in and provided several million tanks to private households, many of which continue to be used.[53] This is one of the largest examples of self-supply of water worldwide.
  • In Bermuda, the law requires all new construction to include rainwater harvesting adequate for the residents.[54]
  • New Zealand has plentiful rainfall in the West and South, and rainwater harvesting is the normal practice in many rural areas, using roof water directed by spouting into covered, 1000 litre storage tanks, with the encouragement of most local councils.[55]
  • In Sri Lanka, rainwater harvesting has been a popular method of obtaining water for agriculture and for drinking purposes in rural homes. The legislation to promote rainwater harvesting was enacted through the Urban Development Authority (Amendment) Act, No. 36 of 2007.[56] The Lanka Rainwater Harvesting Forum is leading Sri Lanka's initiative.[57] The tank cascade system is an ancient irrigation system spanning the island of Sri Lanka.

History

[edit]

The construction and use of cisterns to store rainwater can be traced back to the Neolithic Age, when waterproof lime plaster cisterns were built in the floors of houses in village locations of the Levant, a large area in Southwest Asia, south of the Taurus Mountains, bounded by the Mediterranean Sea in the west, the Arabian Desert in the south, and Mesopotamia in the east. By the late 4000 BC[clarification needed], cisterns were essential elements of emerging water management techniques used in dry-land farming.[58]

Many ancient cisterns have been discovered in some parts of Jerusalem and throughout what is today Israel/Palestine. At the site believed by some to be that of the biblical city of Ai (Khirbet et-Tell), a large cistern dating back to around 2500 BC was discovered that had a capacity of nearly 1,700 m3 (60,000 cu ft). It was carved out of a solid rock, lined with large stones, and sealed with clay to keep it from leaking.[58]

The Greek island of Crete is also known for its use of large cisterns for rainwater collection and storage during the Minoan period from 2,600 BC–1,100 BC. Four large cisterns have been discovered at Myrtos-Pyrgos, Archanes, and Zakroeach. The cistern found at Myrtos-Pyrgos was found to have a capacity of more than 80 m3 (2,800 cu ft) and to date back to 1700 BC.[58]

Around 300 BC, farming communities in Balochistan (now located in Pakistan, Afghanistan, and Iran), and Kutch, India, used rainwater harvesting for agriculture and many other uses.[59] Rainwater harvesting was done by Chola kings as well.[60] Rainwater from the Brihadeeswarar temple (located in Balaganapathy Nagar, Thanjavur, India) was collected in Shivaganga tank.[61] During the later Chola period, the Vīrānam tank was built (1011 to 1037 AD) in the Cuddalore district of Tamil Nadu to store water for drinking and irrigation purposes. Vīrānam is a 16-km-long tank with a storage capacity of 1,465,000,000 cu ft (41,500,000 m3).

Rainwater harvesting was also common in the Roman Empire.[62] While Roman aqueducts are well-known, Roman cisterns were also commonly used and their construction expanded with the Empire.[58] For example, in Pompeii, rooftop water storage was common before the construction of the aqueduct in the 1st century BC.[63] This history continued with the Byzantine Empire; for example, the Basilica Cistern in Istanbul.

Though little known, the town of Venice for centuries depended on rainwater harvesting. The lagoon surrounding Venice is brackish water, which is unsuitable for drinking. Venice's ancient inhabitants established a rainwater collection system based on man-made insulated collection wells.[64] Water percolated down the specially designed stone flooring, and was filtered by a layer of sand, then collected at the bottom of the well. Later, as Venice acquired territories on the mainland, it started to import water by boat from local rivers. Still, the wells remained in use and were especially important in times of war when an enemy could block access to the mainland water.

See also

[edit]

References

[edit]
  1. ^ a b Staddon, Chad; Rogers, Josh; Warriner, Calum; Ward, Sarah; Powell, Wayne (2018-11-17). "Why doesn't every family practice rainwater harvesting? Factors that affect the decision to adopt rainwater harvesting as a household water security strategy in central Uganda". Water International. 43 (8): 1114–1135. Bibcode:2018WatIn..43.1114S. doi:10.1080/02508060.2018.1535417. ISSN 0250-8060. S2CID 158857347.
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  4. ^ Kinkade-Levario, Heather (2007). Design for Water : Rainwater Harvesting, Stormwater Catchment, and Alternate Water Reuse. Gabriola Island, B.C.: New Society Publishers. p. 27. ISBN 978-0-86571-580-6.
  5. ^ Bagel, Ravi; Stepan, Lea; Hill, Joseph K.W. (2017). Water, knowledge and the environment in Asia : epistemologies, practices and locales. London. ISBN 9781315543161.{{cite book}}: CS1 maint: location missing publisher (link)
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  17. ^ O'Brien, Sara Ashley (2014-11-11). "The Tech Behind Smart Cities - Eliminating Water Pollution". CNN Money. Archived from the original on 2014-11-14. Retrieved 13 November 2014.
  18. ^ Braga, Andrea. "Making Green Work, and Work Harder" (PDF). Geosyntec. p. 5. Archived from the original (PDF) on 4 March 2016. Retrieved 30 November 2014.
  19. ^ "Rain fed solar-powered water purification systems". Archived from the original on 21 October 2017. Retrieved 21 October 2017.
  20. ^ "Inverted Umbrella Brings Clean Water & Clean Power To India". 2017-12-04. Archived from the original on 2018-07-09. Retrieved 5 December 2017.
  21. ^ a b "New rooftop solar hydro panels harvest drinking water and energy at the same time". 29 November 2017. Archived from the original on 2019-08-10. Retrieved 2017-11-30.
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