Rain Water Harvesting for a Proposed Building
1. What is
rainwater harvesting?
Rainwater
harvesting is a technology used to collect, convey and store rain for later use
from relatively clean surfaces such as a roof, land surface or rock catchment.
The water is generally stored in a rainwater tank or directed to recharge
groundwater. Rainwater infiltration is another aspect of rainwater harvesting
playing an important role in storm water management and in the replenishment of
the groundwater levels. Rainwater harvesting has been practiced for over 4,000
years throughout the world, traditionally in arid and semi-arid areas, and has
provided drinking water, domestic water and water for livestock and small
irrigation.
Today,
rainwater harvesting has gained much on significance as a modern, water-saving
and simple technology. The practice of collecting rainwater from rainfall
events can be classified into two broad categories: land-based and roof-based.
Land-based rainwater harvesting occurs when runoff from land surfaces is
collected in furrow dikes, ponds, tanks and reservoirs. Roof-based rainwater
harvesting refers to collecting rainwater runoff from roof surfaces which
usually provides a much cleaner source of water that can be also used for
drinking.
Gould
and Nissen-Petersen (1999) categorised rainwater harvesting according to the
type of catchment surface used and the scale of activity
2. Why
rainwater harvesting?
In
many regions of the world, clean drinking water is not always available and
this is only possible with tremendous investment costs and expenditure.
Rainwater is a free source and relatively clean and with proper treatment it
can be even used as a potable water source. Rainwater harvesting saves
high-quality drinking water sources and relieves the pressure on sewers and the
environment by mitigating floods, soil erosions and replenishing groundwater
levels. In addition, rainwater harvesting reduces the potable water consumption
and consequently, the volume of generated wastewater.
3.
Application areas
Rainwater
harvesting systems can be installed in both new and existing buildings and
harvested rainwater used for different applications that do not require
drinking water quality such as toilet flushing, garden watering, irrigation,
cleaning and laundry washing. Harvested rainwater is also used in many parts of
the world as a drinking water source. As rainwater is very soft there is also
less consumption of washing and cleaning powder. With rainwater harvesting, the
savings in potable water could amount up to 50% of the total household
consumption.
4.
Criteria for selection of rainwater harvesting technologies
Several
factors should be considered when selecting rainwater harvesting systems for
domestic use:
·
Type
and size of catchment area
·
Local
rainfall data and weather patterns
·
Family
size
·
Length
of the drought period
·
Alternative
water sources
·
Cost
of the rainwater harvesting system.
When
rainwater harvesting is mainly considered for irrigation, several factors
should be taken into consideration. These include:
·
Rainfall
amounts, intensities, and evapo-transpiration rates
·
Soil
infiltration rate, water holding capacity, fertility and depth of soil
·
Crop
characteristics such as water requirement and length of growing period
·
Hydrogeology
of the site
·
Socio-economic
factors such as population density, labour, costs of materials and regulations
governing water resources use.
5.
Components of a rooftop rainwater harvesting system
Although
rainwater can be harvested from many surfaces, rooftop harvesting systems are
most commonly used as the quality of harvested rainwater is usually clean
following proper installation and maintenance. The effective roof area and the
material used in constructing the roof largely influence the efficiency of
collection and the water quality.
Rainwater harvesting systems
generally consist of four basic elements:
1. A collection (catchment) area
2. A conveyance system consisting of
pipes and gutters
3. A storage facility, and
4. A delivery system consisting of a tap
or pump.
Figure
2 shows a simple schematic diagram of a rooftop rainwater harvesting system
including conveyance and storage facilities.
1. A collection or catchment system is generally a simple structure such
as roofs and/or gutters that direct rainwater into the storage facility. Roofs
are ideal as catchment areas as they easily collect large volumes of rainwater.
The
amount and quality of rainwater collected from a catchment area depends upon
the rain intensity, roof surface area, type of roofing material and the
surrounding environment. Roofs should be constructed of chemically inert
materials such as wood, plastic, aluminium, or fibreglass. Roofing materials
that are well suited include slates, clay tiles and concrete tiles. Galvanised
corrugated iron and thatched roofs made from palm leaves are also suitable.
Generally, unpainted and uncoated surface areas are most suitable. If paint is
used, it should be non-toxic (no lead-based paints).
2. A conveyance system is required to transfer the
rainwater from the roof catchment area to the storage system by connecting roof
drains (drain pipes) and piping from the roof top to one or more downspouts
that transport the rainwater through a filter system to the storage tanks.
Materials suitable for the pipework include polyethylene (PE), polypropylene
(PP) or stainless steel.
Before
water is stored in a storage tank or cistern, and prior to use, it should be
filtered to remove particles and debris. The choice of the filtering system
depends on the construction conditions.
Low-maintenance
filters with a good filter output and high water flow should be preferred.
“First flush” systems which filter out the first rain and diverts it away from
the storage tank should be also installed. This will remove the contaminants in
rainwater which are highest in the first rain shower.
3. Storage tank or cistern to store harvested rainwater for
use when needed. Depending on the space available these tanks can be
constructed above grade, partly underground, or below grade. They may be
constructed as part of the building, or may be built as a separate unit located
some distance away from the building.
The
storage tank should be also constructed of an inert material such as reinforced
concrete, ferrocement (reinforced steel and concrete), fibreglass,
polyethylene, or stainless steel, or they could be made of wood, metal, or
earth. The choice of material depends on local availability and affordability.
Various types can be used including cylindrical ferrocement tanks, mortar jars
(large jar shaped vessels constructed from wire reinforced mortar) and single
and battery (interconnected) tanks. Polyethylene tanks are the most common and
easiest to clean and connect to the piping system. Storage tanks must be opaque
to inhibit algal growth and should be located near to the supply and demand
points to reduce the distance water is conveyed. Water flow into the storage
tank or cistern is also decisive for the quality of the cistern water. Calm
rainwater inlet will prevent the stirring up of the sediment. Upon leaving the
cistern, the stored water is extracted from the cleanest part of the tank, just
below the surface of the water, using a floating extraction filter. A sloping
overflow trap is necessary to drain away any floating matter and to protect
from sewer gases. Storage tanks should be also kept closed to prevent the entry
of insects and other animals.
4. Delivery system which delivers rainwater and it usually includes a small pump, a
pressure tank and a tap, if delivery by means of simple gravity on site is not
feasible.
Disinfection
of the harvested rainwater, which includes filtration and/or ozone or UV
disinfection, is necessary if rainwater is to be used as a potable water
source.
6. Storage
tanks or reservoirs
The
storage reservoir is usually the most expensive part of the rainwater
harvesting system such that a careful design and construction is needed. The
reservoir must be constructed in such a way that it is durable and watertight
and the collected water does not become contaminated.
All rainwater tank designs should
include as a minimum requirement:
·
A
solid secure cover
·
A
coarse inlet filter
·
An
overflow pipe
·
A
manhole, sump, and drain to facilitate cleaning
·
An
extraction system that does not contaminate the water, e.g. a tap or pump.
Storage
reservoirs for domestic rainwater harvesting are classified in two categories:
1) Surface or above-ground tanks, most
common for roof collection, and
2) Sub-surface or underground tanks,
common for ground catchment systems.
Materials
and design for the walls of sub-surface tanks or cisterns must be able to
resist the soil and soil water pressures from outside when the tank is empty.
Tree roots can also damage the structure below ground.
The
size of the storage tank needed for a particular application is mainly
determined by the amount of water available for storage (a function of roof
size and local average rainfall), the amount of water likely to be used (a
function of occupancy and use purpose) and the projected length of time without
rain (drought period).
7. First
flush and filter screens
The
first rain drains the dust, bird droppings, leaves, etc. which are found on the
roof surface. To prevent these pollutants from entering the storage tank, the
first rainwater containing the debris should be diverted or flushed. Automatic
devices that prevent the first 20-25 litres of runoff from being collected in
the storage tank are recommended.
Screens
to retain larger debris such as leaves can be installed in the down-pipe or at
the tank inlet. The same applies to the collection of rain runoff from a hard
ground surface. In this case, simple gravel-sand filters can be installed at
the entrance of the storage tank to filter the first rain.
8.
Rainwater harvesting efficiency
The
efficiency of rainwater harvesting depends on the materials used, design and
construction, maintenance and the total amount of rainfall. A commonly used
efficiency figure, runoff coefficient, which is the percentage of precipitation
that appears as runoff, is 0.8.
For
comparison, if cement tiles are used as a roofing material, the year-round roof
runoff coefficient is about 75%, whereas clay tiles collect usually less than
50% depending on the harvesting technology. Plastic and metal sheets are best
with an efficiency of 80-90%.
For
effective operation of a rainwater harvesting system, a well designed and
carefully constructed gutter system is also crucial. 90% or more of the
rainwater collected on the roof will be drained to the storage tank if the
gutter and down-pipe system is properly fitted and maintained. Common materials
for gutters and down-pipes are metal and plastic, but also cement-based
products, bamboo and wood can be used.
9.
Designing a rainwater harvesting system
For
the design of a rainwater harvesting system, rainfall data is required
preferably for a period of at least 10 years. The more reliable and specific
the data is for the location, the better the design will be. Data for a given
area can be obtained at the meteorological departments, agricultural and
hydrological research centres and airports.
One
simple method of determining the required storage volume, and consequently the
size of the storage tank, is shown below:
With
an estimated water consumption of 20 l/c*d, which is the commonly accepted
minimum, the water demand will be = 20 x n x 365 l/year, where n=number of
people in the household. If there are five people in the household then the
annual water demand is 36,500 litres or about 3,000 l/month. For a dry period
of four months, the required minimum storage capacity would be about 12,000
litres.
As rainwater supply depends on the annual rainfall, roof
surface and the runoff coefficient, the amount of rainwater that can be
collected = rainfall (mm/year) x area (m2) x runoff coefficient.
As
an example: a metal sheet roof of 80 m2 with 800 mm rainfall/year will yield =
80 x 800 x 0.8 = 51,200 l/year.
Figure
3 demonstrates the cumulative roof runoff (m3) over a one-year period and the
cumulative water demand (m3). The greatest distance between these two lines
gives the required storage volume (m3) to minimise the loss of rainwater.
10. Types
of rainwater use
Rainwater
systems can be classified according to their reliability, yielding four types
of user regimes:
·
Occasional
- water is stored for only a few days in a small container. This is suitable
when there is a uniform rainfall pattern with very few days without rain and
when a reliable alternative water source is available.
·
Intermittent - in situations with one long rainy season when all water demands are
met by rainwater. During the dry season, water is collected from other sources.
·
Partial -
rainwater is used throughout the year but the 'harvest' is not sufficient for
all domestic demands. For example, rainwater is used for drinking and cooking,
while for other domestic uses (e.g. bathing and laundry) water from other
sources is used.
·
Full - for
the whole year, all water for all domestic purposes comes from rainwater. In
such cases, there is usually no alternative water source other than rainwater,
and the available water should be well managed, with enough storage to bridge
the dry period.
Which
of the user regimes to be followed depends on many variables including rainfall
quantity and pattern, available surface area and storage capacity, daily
consumption rate, number of users, cost and affordability, and the presence of
alternative water sources.
11. Benefits
of rainwater harvesting
Rainwater
harvesting in urban and rural areas offers several benefits including provision
of supplemental water, increasing soil moisture levels for urban greenery,
increasing the groundwater table via artificial recharge, mitigating urban
flooding and improving the quality of groundwater. In homes and buildings,
collected rainwater can be used for irrigation, toilet flushing and laundry.
With proper filtration and treatment, harvested rainwater can also be used for
showering, bathing, or drinking. The major benefits of rainwater harvesting are
summarised below:
·
Rainwater
is a relatively clean and free source of water
·
Rainwater
harvesting provides a source of water at the point where it is needed
·
It
is owner-operated and managed
·
It
is socially acceptable and environmentally responsible
·
It
promotes self-sufficiency and conserves water resources
·
Rainwater
is friendly to landscape plants and gardens
·
It
reduces stormwater runoff and non-point source pollution
·
It
uses simple, flexible technologies that are easy to maintain
·
Offers
potential cost savings especially with rising water costs
·
Provides
safe water for human consumption after proper treatment
·
Low
running costs
·
Construction,
operation and maintenance are not labour-intensive.
12.
Disadvantages
The
main disadvantages of rainwater harvesting technologies are the limited supply
and uncertainty of rainfall. Rainwater is not a reliable water source in times
of dry periods or prolonged drought. Other disadvantages include:
·
Low
storage capacity which will limit rainwater harvesting, whereas, increasing the
storage capacity will add to the construction and operating costs making the
technology less economically feasible
·
Possible
contamination of the rainwater with animal wastes and organic matter which may
result in health risks if rainwater is not treated prior to consumption as a
drinking water source
·
Leakage
from cisterns can cause the deterioration of load-bearing slopes
·
Cisterns
and storage tanks can be unsafe for small children if proper access protection
is not provided.
13.
Sustainability
Rainwater
harvesting is one of the most promising alternatives for supplying water in the
face of increasing water scarcity and escalating demand. The pressure on water
supplies, increased environmental impact from large projects and deteriorating
water quality, constrain the ability to meet the demand for freshwater from
traditional sources. Rainwater harvesting presents an opportunity for the
augmentation of water supplies allowing the same time for self-reliance and
sustainability.
14.
Cultural acceptability
Rainwater
harvesting is an accepted freshwater augmentation technology in many parts of
the world. While the bacteriological quality of rainwater collected from ground
catchments is poor, rainwater from properly maintained rooftop catchment
systems, which are equipped with tight storage tanks and taps, is generally
suitable for drinking and often meets the WHO drinking water standards. This
water is generally of higher quality than most traditional water sources found
in the developing world. Rooftop catchment of rainwater can provide good
quality water which is clean enough for drinking, as long as the rooftop is
clean, impervious and made from non-toxic materials and located away from
over-hanging trees.
15.
Maintenance
Maintenance
is generally limited to the annual cleaning of the tank and regular inspection
and cleaning of gutters and down-pipes. Maintenance typically consists of the
removal of dirt, leaves and other accumulated material. Cleaning should take
place annually before the start of the major rainfall season. Filters in the
inlet should be inspected every about three months. Cracks in storage tanks can
create major problems and should be repaired immediately.
16.
Regulations and technical standards
The
most important aspect during the construction of a rainwater harvesting system
is to completely separate the rainwater and drinking water networks. All
rainwater pipework and tapping points should be clearly designated and secured
against unauthorised use.
In
Germany, the construction of a rainwater harvesting system does not require a
building approval but it is advisable to report it to the local public health
office as well as the local water supplier. Some regulations and standards
(especially DIN 1989) should be taken into consideration during construction
and maintenance of a rainwater harvesting system.
17.
Effectiveness of technology
The
feasibility of rainwater harvesting in a particular locality is highly
dependent on the amount and intensity of rainfall. As rainfall is usually
unevenly distributed throughout the year, rainwater harvesting can usually only
serve as a supplementary source of household water. The viability of rainwater
harvesting systems is also a function of the quantity and quality of water available
from other sources, household size, per capita water requirements and available
budget.
Accounts
of serious illness linked to rainwater supplies are few, suggesting that
rainwater harvesting technologies are effective sources of water supply. It
would appear that the potential for slight contamination of roof runoff from
occasional bird droppings does not represent a major health risk. Nevertheless,
placing taps at about 10 cm above the base of the rainwater storage tanks
allows any debris entering the tank to settle on the bottom, where it will not
affect the quality of the stored water, provided it remains undisturbed.
Finally,
effective water harvesting schemes require community participation which is
enhanced by:
·
Sensitivity
to people’s needs
·
Indigenous
knowledge and local expertise
·
Full
participation and consideration of gender issues, and
·
Taking
consideration of prevailing farming systems as well as national policies and
community by-laws.
18.
Economic efficiency
Valid
data on the economic efficiency of rainwater harvesting systems is not
possible. Dependent on the regional conditions (water and wastewater prices,
available subsidies), the amortisation period may vary between 10 and 20 years.
However, it should be taken into consideration that for the major investment
(storage and pipe work) a period of use of several decades is expected.
19. Costs
The
associated costs of a rainwater harvesting system are for installation,
operation and maintenance. Of the costs for installation, the storage tank
represents the largest investment which can vary between 30 and 45% of the
total cost of the system dependent on system size. A pump, a pressure
controller and fittings in addition to plumber’s labour represent other major
costs of the investment.
In
general, a rainwater harvesting system designed as an integrated element of a
new construction project is more cost-effective than retrofitting a system.
This can be explained by the fact that many of the shared costs (such as for
roofs and gutters) can be designed to optimise system performance and the
investment can be spread over time.
20.
Rainwater quality standards
The
quality of rainwater used for domestic supply is of vital importance because,
in most cases, it is used for drinking. Rainwater does not always meet drinking
water standards especially with respect to bacteriological water quality.
However, just because water quality does not meet some arbitrary national or
international standards, it does not automatically mean that the water is
harmful to drink.
Compared
with most unprotected traditional water resources, drinking rainwater from
well-maintained roof catchments is usually safe, even if it is untreated. The
official policy of the Australian Government towards the question “Is rainwater
safe to drink?” is as follows: “Providing the rainwater is clear, has little
taste or smell and is from a well-maintained system, it is probably safe and
unlikely to cause any illness for most users”. For immuno-compromised persons,
however, it is recommended that rainwater is disinfected through boiling prior
to consumption.
21.
Drinking water from rainwater
In
many countries of the world where water resources are not available at a
sufficient quality fit for human consumption, rainwater acts as a substitute
for drinking water and other domestic uses. In some remote islands around the
globe, rainwater may even act as the major potable water source for their
population.
The
most important issue in collecting rainwater is keeping it free of dirt such as
leaves, bird droppings and dead animals, and avoiding contamination with
pollutants like heavy metals and dust.
Rainwater
can be also treated for use as a potable water source. The use of slow sand
filtration has proved to be a simple and effective treatment technology for the
elimination of most of the organic and inorganic pollutants that may be present
in rainwater, as well as producing a virtually pathogen-free water for
drinking.
RAINWATER HARVESTING
Rainwater harvesting is the
accumulating and storing of rainwater for reuse before it reaches the aquifer.
It has been used to provide drinking water, water for livestock, water for
irrigation, as well as other typical uses. Rainwater collected from the roofs
of houses and local institutions can make an important contribution to the
availability of drinking water. It can supplement the subsoil water level and
increase urban greenery.
Water collected from the ground,
sometimes from areas that are especially prepared for this purpose, is called
Stormwater harvesting. In some cases, rainwater may be the only available, or
economical, water source. Rainwater harvesting systems can be simple to
construct from inexpensive local materials, and are potentially successful in
most habitable locations. Roof rainwater may not he potable and may require
treatment before consumption. As rainwater rushes from your roof it may carry
pollutants, such as mercury from coal burning buildings or bird faeces.
Although some rooftop materials may
produce rainwater that would be harmful to human health as drinking water, it
can he useful in flushing toilets, washing clothes, watering the garden and
washing cars these uses alone have the amount of water used by a typical home,
Household rainfall catchment systems are appropriate in areas with an average
rainfall greater than 200 mm (7.9 in) per year, and no other accessible water
sources (Skinner and Cotton, 1992). Overflow from rainwater harvesting tank
systems can be used to refill aquifers in a process called groundwater recharge
though this is a related process, it must not be confused with rainwater
harvesting.
There are several types of systems to
harvest rainwater, ranging from very simple home systems to complex industrial
systems. The rate at which water can be collected from either system is
dependent on the plan area of the system, its efficiency, and the intensity of
rainfall (i.e., annual precipitation (mm per annum) x square meter of
catch.rnent area litres per annum yield) ... a 200 square meter roof catchment
catching 1,000mm PA yields 200 kLPA.
Id be large enough to carry peak
flows. Storage tanks should be covered to prevent mosquito breeding and to
reduce evaporation losses, contamination and algal growth.
A subsurface dike is built in an aquifer
to obstruct the natural flow of groundwater, thereby raising the groundwater
level and increasing the amount of water stored in the aquifer. The sub-surface
dike at Krishi Vigyan Kendra Kannur under Kerala Agricultural
University
Groundwater recharge
Rainwater may also be used for
groundwater recharge, where the runoff on the ground is collected and allowed
to he absorbed adding to the groundwater. In the US, rooftop rainwater is
collected and stored in sump.
Advantages in urban areas
Rainwater harvesting can ensure an
independent water supply during water restrictions, though somewhat dependent
on end-use and maintenance, usually of acceptable quality for household needs
and renewable at acceptable volumes, despite forecasted climate change (CSIRO,
2003). It produces beneficial externalities by reducing peak storm water runoff
and processing costs.
In municipalities with combined sewer
systems, reducing storm runoff is especially important, because excess runoff’
during heavy storms leads to the discharge of raw sewage from outfalls when
treatment plant capacity cannot handle the combined flow. Rainwater harvesting
systems are simple to install and operate. Running costs are negligible, and
they provide water at the point of consumption. Rainwater harvesting in urban
communities has been made possible by various companies. Their tanks provide an
attractive yet effective solution to rainwater catchment.
Quality
As rainwater may be contaminated due
to pollutants like microscopic germs etc., 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 human, animal and bird faces, 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; 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 the Gansu province for example, harvested
rainwater is boiled in parabolic solar cookers before being used for drinking.
In Brazil alum and chlorine is added to disinfect water before corisun1ption.
So-called appropriate technology” methods, such as solar water disinfection,
provide low-cost disinfection options for treatment of stored rainwater for
drinking.
System sizing
It is important that the system is
sized to meet the water demand throughout the dry season. In general, the size
of the storage tank should be big enough to meet the daily water requirement
throughout the dry season. In addition, the size of the catchment area or roof
should be large enough to fill the tank.
Around the world
Ancient period
Rainwater harvesting has been used
since biblical times. It was done in ancient Palestine, Greece and Rome. Around
3rd Century BC., fanning communities in Baluchistan and Kutch used it for
irrigation.141 In Ancient Tamil Nadu, India, Rainwater harvesting weie done by
Chola kings.
Now
·
Currently in
China and Brazil rooftop rainwater harvesting is being practiced for providing
drinking water, domestic water, water for livestock, water for small irrigation
and a way to replenish ground water levels. Gansu province in China and
semi-arid north east Brazil have the largest rooftop rainwater harvesting
projects ongoing.
·
In Bermuda the
law requires all new construction to include rainwater harvesting adequate for
the residents.
·
The U.S. Virgin
Islands have a similar law.
·
In Senegal and
Guinea-Bissau, the houses of the Diola-people are frequently equipped with
homebrew rainwater harvesters made from local, organic materials.
·
In the United
Kingdom water butts are often found in domestic gardens to collect rainwater,
which is then used to water the garden. However, the British govemment1s Code
For Sustainable Homes encourages fitting large underground tanks to new-build
homes to collect rainwater for flushing toilets, washing clothes, watering the
garden, and washing cars. This reduces by 50% the amount of mains water used by
the home.
·
In the Irrawaddy
Delta of Myanmar, the groundwater is saline and communities rely on mud- lined
rainwater ponds to meet their drinking water needs throughout the dry season.
Some of these ponds are centuries old and are treated with great reverence and
respect.
·
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 rights to take water from the watershed. Now, residential well owners
that meet certain criteria may obtain a pennit to install a roojiop precipitation
collection system (SB 09080).171 Up to 10 large scale pilot studies may also he
permitted (HB 09-1 l29).[81 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. In Colorado
·
In Beijing some
housing societies are now adding rain water in their main water sources after
proper treatment.
Professor Micheal McGinley established
a project to design a rain water harvesting prototype in the Biosystems design
Challenge Module in University College Dublin.
·
In Australia
rainwater harvesting is typically used to supplement the reticulated mains
supply. In south east Queensland, households that harvested rainwater doubled
each year from 2005 to 2008, reaching 40% penetration at that time (White, 2009
(PhD)).
·In India
·
In Tamil Nadu,
India rainwater harvesting was made compulsory for every building to avoid
ground water depletion. It proved excellent results within five years and every
other state took it as role model. Since the implementation, Chennai saw 50 per
cent rise in water level in five years and the water quality significantly
improved.
·
In Rajasthan,
India rainwater harvesting has traditionally been practiced by the people of
the Thar Desert. There are many ancient water harvesting systems in Rajasthan,
which have now been revived.
·
Kerala, India,
ESTIMATE OF RAIN WATER HARVESTING
SYSTEM FOR PROPOSED TMC BUILDING
|
Item No.
|
Details of Particulars
|
Qty
|
Unit
|
Rate
|
Per
|
Amount
|
|
1
|
110mm PVC pipie
|
200
|
Mm
|
78.00
|
/m
|
15000.00
|
|
2
|
110mm Pipe Bents
|
6
|
Each
|
55.00
|
Each
|
330.00
|
|
3
|
Coupling for Joining
|
8
|
Each
|
45.00
|
Each
|
360.00
|
|
4
|
Clamp for Fixing
|
16
|
Each
|
25.00
|
Each
|
400.00
|
|
|
Grand Total
|
19090.00
|
||||
ESTIMATE OF RAIN WATER HARVESTING tank FOR TMC BUILDING
|
Item
No.
|
Particular
Items and Details of Works
|
No
|
L
|
B
|
Ht
or Depth m
|
Qty
|
Explanatory
Notes
|
|
1
|
Earth work in excavation
for water tank
|
1
|
6
|
3
|
1.5
|
27
|
Cum
|
|
2
|
Cement concrete 1:3:6 in
foundation
|
1
|
6
|
3
|
0.15
|
2.7
|
Cum
|
|
3
|
1st class brick
work in 1:4 cement mortar in septic tank
|
|
|
|
|
|
|
|
|
Long wall
|
2
|
6
|
0.3
|
1.5
|
5.4
|
Cum
|
|
|
Short wall
|
2
|
3
|
0.3
|
1.5
|
2.7
|
Cum
|
|
4
|
12 mm plastering inside
septic tank with 1:2 cement mortar mixed with water proofing compound
|
|
|
|
|
|
|
|
|
Long wall
|
2
|
6
|
0.12
|
1.5
|
2.16
|
Cum
|
|
|
Short wall
|
2
|
3
|
0.12
|
1.5
|
1.08
|
Cum
|
|
5
|
1x1m filtration chamber
|
4
|
1
|
0.3
|
1
|
1.2
|
Cum
|
ABSTRACT FOR WATER TANK PROPOSED
TMC BUILDING
|
Item No.
|
Details of Item of Work
|
Qty
|
Unit
|
Rate
|
Per
|
Amount
|
|
1
|
Earth work in
excavation for water tank
|
27
|
Cum
|
133.00
|
/cum
|
3591.00
|
|
2.
|
Cement concrete
1:3:6 in foundation
|
2.7
|
Cum
|
3328.00
|
/cum
|
8985.60
|
|
3
|
1st
class brick work in 1:4 cement mortar in septic tank
|
|
|
|
|
|
|
|
Long wall
|
5.4
|
Cum
|
6184.00
|
/cum
|
33393.60
|
|
|
Short wall
|
2.7
|
Cum
|
6184.00
|
/cum
|
16696.80
|
|
4
|
12 mm
plastering inside septic tank with 1:2 cement mortar mixed with water
proofing compound
|
|
|
|
|
|
|
|
Long wall
|
2.16
|
Cum
|
102.00
|
/cum
|
220.32
|
|
|
Short wall
|
1.08
|
Cum
|
102.00
|
/cum
|
110.16
|
|
5
|
1x1m
filtration chamber
|
1.2
|
Cum
|
6184.00
|
/cum
|
7420.80
|
|
|
Grand Total : 70418.28
|
|||||
REFERENCES
·
DIN
1989-1. 2002. Rainwater Harvesting Systems – Part 1: Planning, Installation,
Operation and Maintenance. German Institute for Standardisation, Berlin, 2002.
·
Gould,
J. and Nissen-Petersen, E. (1999) Rainwater Catchment Systems for Domestic
Supply: Design, construction and implementation. IT Publications, London
·
Rainwater
Harvesting Project at the Development Technology Unit of School of Engineering,
University of Warwick, UK
·
http://www.eng.warwick.ac.uk/DTU
·
www.wikipedia.com
·
www.google.com
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