Overview

Rainwater Systems collect water run-off rainwater for environmental management, domestic, and agricultural use.[1] Rainwater systems can be traced back to ancient civilizations who would collect water falling on there roofs in a process called rainwater harvesting (RWH). Recently, rainwater harvesting has increased in popularity as people begin searching for more sustainable buildings. However, a majority of water systems today are still not concerned about harvesting rainwater; instead, most water systems transport the rainwater to bodies of water through gutters, inlets, and storm sewers.

Conventional Rainwater Systems


Conventional rainwater systems divert rainwater into bodies of water in order to prevent flooding. Gutters, ditches, and other small scale water relocation devices are often called minor rainwater systems.[2] The main purpose of these minor systems is to collect rainwater from the roofs of buildings and transport it to larger systems that can handle larger volumes of water.

gutter.jpg
Figure 1: Gutters and downspouts are one example of minor rainwater systems
Larger rainwater systems are typically called major rainwater systems. Major rainwater systems typically are used to both transport and filter large amounts of rainwater. Examples of major rainwater systems include storm sewers, water retention ponds, and water treatment plants. Figure 2 illustrates how the rainwater flows through major rainwater systems before it is released into a lake or river.[3]

Occasionally, rainwater is treated before it is discharged. One of the simplest ways to treat rainwater is by using a water retention pond. Water retention ponds are like water detention pods however the water is released from the top of the pond so that some water is in the pond at all times.[4] The primary goal of a water retention pond is to reduce the peak rate of surface runoff like a water detention pond. The second goal of a water retention pond is to remove some of the pollution in the water.[5] Pollutants are removed from the water because they settle to the bottom of the pond before the water is discharged.[6] In addition to using retention ponds, rainwater could also be treated by diverting the water to a wastewater treatment plant where the rainwater would be combined with sanitary waste. Treating rainwater is a good way to promote sustainability because untreated water can contain hazardous chemicals like motor oil and pesticides that may harm the environment.[7]

Rainwater Harvesting (RWH)


Rainwater harvesting is the collection and storage of rainwater for later use.[8] Rainwater harvesting has become extremely popular recently because of recent shortages of safe drinking water across the world. According to the World Health Organization, about 6000 children die every day due to not having safe drinking water.[9] However, the lack of safe drinking water is not just limited to third world countries. According to the EPA, 36 states anticipate water shortages during the next two decades of this century.[10] Rainwater harvesting can help prevent water shortages and allow for buildings to be more sustainable by capturing rainwater before it is contaminated as it washes away.

History of RWH

Ancient civilizations have been using rainwater harvesting systems for thousands of years. There is evidence of rainwater harvesting in 2600 B.C in the ancient Harappan civilization in modern day Pakistan.[11] The Harappans used tanks to store rainwater; this water was then used for agricultural purposes.[12] Rainwater harvesting continued to be an important part of ancient society until wells and pipes allowed for water to be transported more effectively. Recently, rainwater harvesting has become more popular due to greater demand for clean wat especially in India and other parts of southeast Asia were clean water is not easily accessible.

Simple RWH Systems

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Figure 3: This simple RWH system includes a catchment (1), delivery system (2), and a storage reservoir (3)

The simplest rainwater systems include a catchment, delivery system, and a storage reservoir (see figure 3).[13] Simple rainwater harvesting systems can be traced beck to 1700 B.C in the island of Crete. Simple rainwater harvesting systems often must have corrugated iron sheets, tiles, or asbestos sheets for roofing in order to divert the rainwater to the gutters and a storage tank.[14] Simple rainwater harvesting systems are especially useful for agricultural use in third world countries.

Filtered RWH Systems

Harvested rainwater that will be used for potable use must include some sort of a filtration system. The main source of rainwater contamination is the organic matter, inter solids, fecal decomposition from birds, and trace amounts of metals.[15] One of the best ways to remove a majority of these pollutants from the harvested rainwater is by using a first flush system. First flush systems remove the rainwater collected at the beginning of a storm because the water collected at the beginning of a storm typically has a much greater amount of pollutants.[16] The longer the dry period before the storm the higher the amount of polluted material in the first flush system.[17] This polluted rainwater that is discharged from the collection system can still be used for agricultural uses. Rainwater is still not always potable after the first flush; so, rainwater must also be treated before it can be used as drinking water.[18] Treating the rainwater often includes filtration and chlorination of the rainwater (see Figure 4).[19]

RWH examples

One example of a large scale filtered rainwater harvesting system is the dormitory at Seoul National University in South Korea. Three of the dormitory buildings combine to have 2098 cubic meters of catchment area which is diverted to a 200 ton storage tank.[20] This rainwater is then filtered, mixed with tap water, and pumped into one of the dormitory buildings. This rainwater harvesting system has dramatically reduced the amount of municipal water that the dormitories require.[21]

A second example of a building that successfully installed a rainwater system one of the buildings on the University of British Columbia's campus called the CIRS building. This building collected the water that fell from the roof and diverted it to large holding bins in the basement of the structure. The water is then filtered and combined with municipal water as it is pumped into the rest of the building.[22]

Benefits of RWH

Rainwater harvesting has many benefits both environmentally and economically. One of the biggest advantages of rainwater harvesting is that it is an easy way to save money on water bills. Simple rainwater harvesting systems without filtration or pumps have virtually no upkeep expenses and can be easily used for watering lawns or agriculture. Non potable harvested water can also be used for toilet flushing in large buildings, which accounts for 30 percent of indoor water use.[23]

Using harvested rainwater improves sustainability because it reduces peoples dependence on water that is removed from aquatic ecosystems like lakes and rivers. Rainwater harvesting systems eliminate the electricity required to pump water from the water treatment. Rainwater harvesting also reduces the amount of water runoff. Reducing the amount of runoff that enters storm sewers can reduce the chances of flooding and erosion after a big storm.

Advanced RWH system.jpg
Figure 4: Complex RWH system with filtration

Problems with RWH
One of the biggest problems with rainwater harvesting is that the water must be filtered in order to be used as drinking water. Many people in third world countries that drink harvested rainwater without filtration can get sick from the bacteria and lead that may be in the water. The energy and upkeep supplies needed to filter the water can also be relatively expensive. These expenses often makes filtered rainwater more expensive than water obtained traditionally.

Recent Research on RWH

A cost-benefit analysis of rainwater harvesting performed by Duke University in 2008 analyzed a rainwater harvesting system in Arlington, Virginia. The study determined that this specific rainwater harvesting system was not cost effective.[24] However, the study noted that while the rainwater harvesting system may be slightly more expensive, the benefits that rainwater harvesting systems have for the environment may overcome the premium price.[25] For more information on the study visit this link.

A similar cost benefit study was performed on the CIRS building at the University of British Columbia. This study found that the rainwater collected from the roof would not be able to service the entire building. However, the rainwater harvesting system did significantly reduce the amount of municipal water needed and reduced the amount of runoff from the building. For more information on this study visit this link.

Conclusion


Rainwater harvesting systems play a key role in both transporting and harvesting rainwater. Rainwater harvesting systems also play a key role in creating a more sustainable world. Rainwater filtration systems protect the environment by preventing hazardous materials from entering lakes and rivers. Secondly, rainwater harvesting systems can reduce the electrical costs of pumping water to homes while at the same time reducing the chance of flooding and erosion. As clean water becomes more scarce in the future, rainwater systems will become much more popular and a more important part of the construction industry.
  1. ^ Worm, J., Hattum, T. (2005). Rainwater harvesting for domestic use,Agromisa Foundation, Wageningen.
  2. ^ Mays, L. W. (2001). Stormwater Collection Systems Design Handbook. New York: McGraw-Hill.
  3. ^ Mays, L. W. (2001). Stormwater Collection Systems Design Handbook. New York: McGraw-Hill.
  4. ^ Johnson , A. (n.d.). Retrieved from http://www.newton.dep.anl.gov/askasci/eng99/eng99219.htm
  5. ^ Yuan, C. (2008). Sediment Discharge from a Storm-Water Retention Pond. Journal Of Irrigation & Drainage Engineering, 134(5), 606-612. doi:10.1061/(ASCE)0733-9437(2008)134:5(606)
  6. ^ Mays, L. W. (2001). Stormwater Collection Systems Design Handbook. New York: McGraw-Hill.
  7. ^ Stormwater Management: Retention Ponds. Retrieved 11-27-2013 from http://www.sustainablecitiesinstitute.org/view/page.basic/class/feature.class/Lesson_Retention_Ponds_Overview
  8. ^ Kloss, C. (2008). Managing Wet Weather with Green Infrastructure, EPA Municipal handbook, EPA.gov
  9. ^ Amin, M. T., & Alazba, A. A. (2011). Probable Sources of Rainwater Contamination In A Rainwater Harvesting System and Remedial Options. Australian Journal Of Basic & Applied Sciences, 5(12), 1054-1064
  10. ^ Kloss, C. (2008). Managing Wet Weather with Green Infrastructure, EPA Municipal handbook, EPA.gov
  11. ^ Pandey, D. N., Gupta, A. K., & Anderson, D. M. (n.d.). Retrieved from https://www.ncdc.noaa.gov/paleo/cv/cv_pubs/Pandey2003.pdf
  12. ^ Pandey, D. N., Gupta, A. K., & Anderson, D. M. (n.d.). Retrieved from https://www.ncdc.noaa.gov/paleo/cv/cv_pubs/Pandey2003.pdf
  13. ^ Worm, J., Hattum, T. (2005). Rainwater harvesting for domestic use,Agromisa Foundation, Wageningen.
  14. ^ Goosen, M. A., & Shayya, W. H. (2000). Water Management, Purification & Conservation in Arid Climates. Lancaster, Pa: Technomic Pub. Co. (62)
  15. ^ Amin, M. T., & Alazba, A. A. (2011). Probable Sources of Rainwater Contamination In A Rainwater Harvesting System and Remedial Options. Australian Journal Of Basic & Applied Sciences, 5(12), 1054-1064.
  16. ^ Amin, T. T., & Han, M. Y. (2011). Microbial quality variation within a rainwater storage tank and the effects of first flush in Rainwater Harvesting (RWH) System. Australian Journal Of Basic & Applied Sciences, 5(9), 1804-1813.
  17. ^ Amin, M. T., & Alazba, A. A. (2011). Probable Sources of Rainwater Contamination In A Rainwater Harvesting System and Remedial Options. Australian Journal Of Basic & Applied Sciences, 5(12), 1054-1064.
  18. ^ Amin, M. T., & Alazba, A. A. (2011). Probable Sources of Rainwater Contamination In A Rainwater Harvesting System and Remedial Options. Australian Journal Of Basic & Applied Sciences, 5(12), 1054-1064.
  19. ^ Hicks, B. (2008). A cost-benefit analysis of rainwater harvesting at commercial facilities in arlington county, virginia. (Master's thesis, Duke University)Retrieved from http://dukespace.lib.duke.edu/dspace/bitstream/handle/10161/512/;jsessionid=BD9B3D6E8098F443C025933399FEEBD0?sequence=1
  20. ^









    Amin, M. T., & Alazba, A. A. (2011). Probable Sources of Rainwater Contamination In A Rainwater Harvesting System and Remedial Options. Australian Journal Of Basic & Applied Sciences, 5(12), 1054-1064.
  21. ^









    Amin, M. T., & Alazba, A. A. (2011). Probable Sources of Rainwater Contamination In A Rainwater Harvesting System and Remedial Options. Australian Journal Of Basic & Applied Sciences, 5(12), 1054-1064.
  22. ^



    http://cirs.ubc.ca/building/building-manual/rainwater-system
  23. ^









    Environment Canada. A Wise Use of Water Guide for Owners and Tenants of Condominiums and Housing Cooperatives. Retrieved from http://www.ec.gc.ca/eau-water/default.asp?lang=En&n=3788622E-1
  24. ^









    Hicks, B. (2008). A cost-benefit analysis of rainwater harvesting at commercial facilities in arlington county, virginia. (Master's thesis, Duke University)Retrieved from http://dukespace.lib.duke.edu/dspace/bitstream/handle/10161/512/;jsessionid=BD9B3D6E8098F443C025933399FEEBD0?sequence=1
  25. ^ Hicks, B. (2008). A cost-benefit analysis of rainwater harvesting at commercial facilities in arlington county, virginia. (Master's thesis, Duke University)Retrieved from http://dukespace.lib.duke.edu/dspace/bitstream/handle/10161/512/;jsessionid=BD9B3D6E8098F443C025933399FEEBD0?sequence=1