Friday 24 November 2006


Basics of Rain Water Harvesting (RWH)
What is RWH?
Rain Water Harvesting is a way to capture the rain water when it rains, store that water above ground or charge the underground and use it later. This happens naturally in open rural areas. But in congested, over-paved metropolitan cities, we need to create methods to capture the rain water.
Rainwater harvesting is the collection and storage of rain from roofs or from a surface catchment for future use. The water is generally stored in rainwater tanks or directed into mechanisms which recharge ground water. This is appropriate in many parts of the world, such as western Britain, China, Brazil, Thailand, Sri Lanka, Germany, Australia and India, where there is enough rain for collection and conventional water resources either do not exist or are at risk of being over-used to supply a large population. Rainwater harvesting can provide lifeline water for human consumption, reduce water bills and the need to build reservoirs which may require the use of valuable land.
Traditionally, rainwater harvesting has been practised 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. This method may have been used extensively by the Indus Valley Civilization.
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 north east Brazil have the largest rooftop rainwater harvesting projects ongoing.
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.
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 (Toronto Healthy House).
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 homes.

A sample urban installation - Roof rainwater collection - in a metropolitan city
• If you live in a single dwelling house or a multi-tenant apartment complex, you already have 80% of the RWH system. We just need re-orient the plumbing design.
• The present design of the house will take all the rainwater from the roof and all the ground level areas surrounding the house and flow the water towards the street. (where it floods the street, clogs the storm drains and sewer lines for a few days, before flowing away as sewage water)
• From the roof tops, bring the rainwater down using closed PVC pipes and direct it to a sump. Include a simple 3-part filteration unit consisting of sand, brick jelly and broken mud bricks
• If you do not have sump, use a well. In many parts of the country, old wells when they go dry, is used as garbage dumps. Please clean the well and put the rain water into it.
• If you do not have a well, construct a baby well (about 2ft in diameter and about 16 feet deep based on soil structure)
• Other types of RWH - collect the ground water and stop their flow at the gate. Put a concrete slab with holes in it, build a 2 feet deep pit, across the full width of the gate. Collect and connect a pipe and flow the water to a well or a baby well.
All costs are subject to local variations in different parts of India. Use these figures for budgetary purposes only.
• Most often, the cost is from the PVC pipes. A 4" diameter PVC pipe costs Rs xx per linear foot. A 5" pipe costs lot more than a 4" pipe.
• If you do not have a sump, include about Rs 5 per litre of water storage. So, a 10,000 litre size sump will cost Rs 50,000. (For a family of 4, using about 80 litres per day per person, this 10,000 litre size sump will contain 1 month's water needs for this family.
• If you do not have old style well - 6' to 8' diameter and about 60 feet deep, it will cost about Rs 5,000.
If you wish to construct a baby well, it may cost around Rs 2,500
• A water tanker bringing water from unknown sources and untested for its quality will cost about Rs 1000 to Rs 2500 for 10,000 litres of water.
• You cannot put a price on 'peace of mind' knowing that you have water for a month.
Did you know that..
• A well is not for storing water. The well connects the surface to the underground water sources. Based on the underground water availability during a rainy season, the water level in the well will go up and down.
• Long after the rains have stopped, the well gets its water from the underground sources leaking into it.
• Where you get water using a bore-well, rain water did percolate through any soil structure at the ground level, including rocky, laterite rock surface.
• Every bore well will eventually go dry, some sooner, some later.
• Use a bore well in reverse. Use a dried up bore well to recharge the underground supply by adding a percolation pit at the top
A sample rural installation - rain water collection - in a small village.
Recognize first that 3 positive aspects of a village as it relates to water harvesting.
1. The village population is about 500+ families or about 1,500+ residents.
2. Most villages don't even have roads. There are no paved parking lots in a village.
3. A villager's house is about 300 sq.feet - whether it is made of a thatched roof or a concrete roof. Even if you collect the rain water from the roof or from the sides, you often find kitchen waste water running in the middle of the street.
What types of RWH makes sense in the rural areas?
a. Build community wells in a few places in the village. Within 10-20 feet from the well, construct a bore-well using a hand-operated pump. Educate the villagers to keep the area around the well and the bore well clean - no washing (human, cattle, motor cycles, clothing), no defecation.
b. If there are existing water tanks in the village, desilt and dredge them every 3 years.
c. If there are any small rivers or streams, build check-dams across them to hold the rain water for usage after the rains have stopped.

Residential Buildings

Single dwelling and Multiple dwelling
RWH installation cost for a single dwelling house in Chennai will cost around Rs 2,000 to Rs 5,000.
Costs for a 5-story flat complex in Chennai with 25 tenants will cost about Rs 60,000 to Rs 80,000.
For Delhi and Mumbai, double the costs.
Describes the 3 types of RWH at the Rain Center in Chennai
RC Pamphlet
A house in Portland OR (USA) with RWH
RWH in Portland OR
A graphic showing the RWH installation in a 2-story house
Note: the excess water from the sump is charged underground
Multi-story schematic

RWH Calculation spread sheet

RWH Calculation spread sheet
Monthly rainfall averages for 19 cities in India are available. Assuming that you are familiar with EXEL sheets, understand the method and parameters used. Unit cost factors are subject to local variation.

Coca-Cola India today set another example in the area of private-public partnership in water conservation with the dedication of one more Rain Water Harvesting Project in the city. The latest Rain Water harvesting has come up at the official residence of the Environment Minister, Government of Uttar Pradesh. The Rain Water Harvesting Project was commissioned under the aegis of Brindavan Bottlers Ltd., the authorized bottler of Coca-Cola. With this project, Coca-Cola India has created fresh annual ground water recharge potential of 450 cubic meters at average rain fall. Amongst those present on the occasion included Shri Ujjawal Raman Singh, Hon’ble Minister for Environment, Government of Uttar Pradesh, Senior Officials of the Environment Ministry, Mr. M. D. Ladhani, Chairman, Brindavan Bottlers Ltd., Mr. Deepak Jolly, Vice President, Public Affairs & Communication, Coca-Cola India, Mr. Vivek Ladhani, Director, Brindavan Bottlers Ltd., Mr. Ashutosh Bharadwaj, Area Operations Director, Coca-Cola and other dignitaries.
In February 2006, Coca-Cola India had commissioned 05 Rain Water Harvesting Projects in the city. These five projects together have the potential to recharge 30,00 cubic meters of ground water annually in normal monsoon. The projects are at Colvin Taluqdar’s College, Gopal Tirath Plaza, Nandgaon The Club, Mahindra Towers and Raja Ram Kumar Plaza in the city. With the commissioning of the latest project, Coca-Cola has created annual ground water recharge potential of 3450 cubic meter in Lucknow city alone in 2006.

Speaking on the occasion, Mr. Deepak Jolly, Vice President, Coca-Cola India, said, “At Coca-Cola, we are following 4 R’s for water conservation – reduce, reuse, recycle and recharge. While 3 R’s that is reduce, reuse and recycle are being followed vigorously at all our bottling units, recharge is an area where we are working with various stakeholders including communities. We share water resources with the local community, therefore we pro-actively work in the area of water conservation through rain water harvesting and restoration of large water bodies, which also helps majorly in ground water recharge. It has also been our endeavour to create awareness on the need of water conservation and ground water recharge. The latest private-public partnership is a step in that direction. I hope that this small but significant step from Coca-Cola will give a big fillip to Rain Water Harvesting initiatives in Uttar Pradesh in general and Lucknow in particular. In all our Rain Water Harvesting projects in Uttar Pradesh, the State Ground Water Board has been an excellent partner”.

In the year 2006, Coca-Cola has so far created fresh annual ground water recharge potential of over 11,708 Cubic Meter in Varanasi alone at the average rain fall through Rain Water Harvesting Projects and revival of two large community ponds. The World Environment Foundation recently conferred “Special Commendation of Golden Peacock Award for Environment Management, 2006”to Mehandiganj Bottling Operation.

Shri Ujjawal Raman Singh, Hon’ble Minister for Environment, Government of Uttar Pradesh said that we are all consumers of water and therefore we should take collective responsibility to ensure that water resources are conserved and protected for the future generation. To maintain water sustainability, it is very crucial that we capture and direct as much rain water as possible into the ground to ensure that the underground water bank is augmented to meet our present and future demands. In this regard, the steps taken by Hindustan Coca-Cola through Rain Water Harvesting are commendable. Hindustan Coca-Cola officials have also told me that they plan to undertake many more such initiatives. I take this opportunity to congratulate and thank Hindustan Coca-Cola for their excellent work in the area of water conservation and ground water recharge. I hope to hear of more such projects being implemented by the company in the future.
There are many types of systems to harvest rainwater. The type used depends on physical and human considerations.
A mechanism can be used to send the initial water flow to waste, usually the first few liters. These are commonly known as 'first-flush' diverters, and are used to ensure that the 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 airborn pollutants being washed from the sky[citation needed], and likewise minimizes contamination of your captured supply.
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,[citation needed] but this may be unwise in different environments.
In India, reservoirs called tankas were used to store water; typically they were shallow with mud walls. Ancient tankas still exist in some places.[citation needed]
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 India this includes johads, or ponds which collect the run-off from small streams in wide area. [1][citation needed]
As rainwater may be contaminated, it is often not considered suitable for drinking without treatment. However, there are many examples of rainwater being used for all purposes — including drinking — following suitable treatment.
Rainwater harvested from roofs can contain 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 the highest concentrations occurring in the first rain immediately after a dry spell;[2] 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.[citation needed] In Brazil alum and chlorine is added to disinfect water before consumption.[citation needed] Appropriate technology methods such as solar water disinfection, provide low-cost disinfection options for treatment of stored rainwater for drinking.


Water filters said...

Your blog got some nice info about the the rain water harvesting. It will surely give a basic idea of how it works.

rain water harvesting india said...

Rainwater is totally free; the only charge is for collection and utilize. It reduces need on the consistorial water supply. This will save money on utility bills. It makes effective use of a very important source. It reduces flooding, erosion, and the circulation to storm water drains. It decreases the contaminants of surface water with sediments, fertilizers and pesticides from rainwater run-off resulting in cleaner lakes, rivers, seas and other receivers of storm water.