RAINWATER HARVESTING : A SUSTAINABLE WATER SUPPLY
TASMANIAN RAIN is rainwater captured on the pristine north west coast of the island of Tasmania, Australia. The water is collected just minutes of where the World Meteorological Organization records the world’s purest air.The rain has traveled eastward via air currents over Antarctica and 10,000 miles of ocean. As a result, TASMANIAN RAIN contains only 17 parts per million of dissolved solids.TASMANIAN RAIN is collected by a custom-designed catchment facility, and never touches the ground. http:www.tasmanianrain.com
The above website was very exciting to me as I graduated from University of Tasmania; but of course during the 70’s, environmental issues were just emerging and of not much interest to the community. However there were Environmentalist groups in Tasmania then, who were opposing the construction of Dams for Hydroelectric power which was the main source of electrical supply for the island.
The website was discovered while I was researching material for a talk I gave to the Institution of Engineers at the recent Colloquium on the sustainable water supply; aka Rainwater Harvesting (RWH).
RWH is an age old technique involving capturing or trapping the rainwater on the roofs or some other surface before it touches the ground and storing it for reuse. It has been practiced in arid and semi -arid regions and in roman villas, Indian old cities and in Balinese temples.
Presently, RWH is gaining recognition as a sustainable means of water supply. This is a result of the paradigm shift in concept of municipal water supply. When cities grow with ever increasing demand for municipal water, it has been traditional to seek new water catchments, construct dams with large water surfaces, build long interstate water pipelines and construct treatment plants.
All the above causes damage to the environment. Biodiversity is affected; treatment consumes chemicals and produces toxic wastes not to discount the CO2 emissions during the construction and operational process.
“The sustainable method of water supply is to capture the rainwater at source where it falls, store and utilized it there.”
From a typical breakdown of water use in a Malaysian home, the water used for toilet flushing (30%), clothes washing (13%), outdoor (7%), and cleaning (8%) amounting 58% of household water consumption in Malaysia, can be replaced by rainwater harvesting. (Baharuddin A., 2007)
The Malaysian government has recognized that RWH contribute towards national water conservation. It has made a commitment to revise the Guidelines for Installing a Rainwater Collection and Utilization System, in
the Ninth Malaysia Plan; ref: item 18.50, Chap 18, of Ninth Malaysia Plan 2006-2010
In 2003, a shopping complex in Petaling Jaya has successfully installed a RWH system and reported a savings of 30% of its monthly water bill.
JPS and NAHRIM has installed and studied RWH in a double storey link house, Mosque and the JPS headquarters building. NAHRIM reported a savings of 34% of the household water consumption and a stored rainwater quality equivalent to Malaysian National WQI Index of Class IIA; ie suitable for recreation and body contact.
Sumida City, Japan has promoted RWH and to date 300 tanks have been installed in the city, whilst it was reported that 750 private and public buildings in Tokyo have installed RWH systems.
At Changi Airport, rainfall from the runways and the surrounding green areas is diverted to two impounding reservoirs. The water is used primarily for non-potable functions such fire-fighting drills and toilet flushing. Such collected and treated water accounts for 28 to 33% of the total water used
In a project at Belss-Luedecke-Strasse,Berlin, rainwater from all roof areas (7,000 m2) is transferred into a an underground cistern together with the runoff from streets, parking spaces and pathways and the water is used for toilet flushing and garden watering.
In St. Thomas, US Virgin Islands, a rainwater utilisation system is a mandatory requirement for a residential building permit. In Bermuda RWH systems are regulated by a Public Health Act which requires that catchments be whitewashed by white latex paint; catchments, tanks, gutters, pipes, vents, and screens must be kept in good repair. Roofs are repainted every two to three years and storage tanks must be cleaned at least once every six years.
In Australia, states are giving rebates and subsidies for installations of RWH systems in an effort to reduce the consumption of municipal water supply. In fact from the following table 36% of households in South Australia are using RWH as the source of potable water supply.
Malaysian Scenario:
In Malaysia, the government shall promote the use of RWH by not only issuing regulations but need to look into financial incentives, rebates and subsidies to encourage the installations of RWH systems.
RWH is sustainable and shall be a part of the water supply system in Malaysia.
Note: The author is a member of the International Rainwater Catchment Systems Association (IRCSA) which aims to promote and advance rainwater catchment systems technology with respect to planning, development, management, science, technology, research and education worldwide; It was founded in August 1989. Biannual international conference has been held since 1989 with the last in Sydney 2007.
The 14th International Rainwater Cistern Systems Conference will be held in Malaysia in 2009.
Check out the following websites related to RWH; http://www.ircsa.org/ ; http://www.irha-h2o.org/; http://www.arcsa.org/; ; www.skywater.jp/ ; http://www.eng.warwick.ac.uk/dtu/rwh/index.html;
