Rainwater harvesting

RAINWATER HARVESTING
BY EDMC
FAYAZ UDDIN
REG: 11105010
PRESENTATIONON

The World Water Crisis
Rapid population
growth, combined with
industrialization, urbanization, ag
ricultural intensification and
water-intensive lifestyles is
resulting in a global water crisis.
In 2000, at least 1.1 billion of
the world’s people - about one in
five – did not have access to safe
water. Asia contains 65 per cent
of the population without safe
water
and Africa 28 per cent.

Bangladesh Water Crisis
Bangladesh’s water crisis affects both rural
and urban areas, and is a matter of both
water scarcity and water quality. In the late
1970 s, approx. four million wells were
drilled to replace the traditional
contaminated surface water sources. The
projects made significant headway, and
mortality due to water-related diseases
declined. However, in 1993, high arsenic
concentrations were discovered in the
groundwater of several wells in western
Bangladesh. Long-term intake of high
concentrations of arsenic from drinking
water gives rise to a number of health
problems, particularly skin disorders.
Internal cancers have also been linked with
arsenic in drinking water.

 The size of the urban
population is
increasing at alarming
rates. Taking into
account the current
groundwater depletion
trend at 2.81 m/y, a
projection has been
made for 2050 and it
predicts that the
groundwater table will
be lowering down to
120 meters by 2050
from the existing
water .

Current Water Supply in Dhaka
Total production capacity of DWASA is 2247.47 Million Liter per
Day (MLD) (both groundwater and surface water. Water supply in
Bangladesh relies mainly on groundwater. In rural areas, more
than 97 percent of the population extracts groundwater to fulfill
drinking water demands. Whereas, 87.72 percent of the Dhaka
city‟s water supply is dependent on groundwater resources. Even
though Dhaka city is surrounded by the four rivers namely
Buriganga, Balu, Turag and Tongi Khal but only 12.28 percent of
supplied water is obtained from these rivers.
Table 1:
Water production scenario of DWASA

Whatcan we do?
some other recommendations to improve the water Crisis in bd may be listed as
follows:
 Surrounding rivers and canals inside should be kept free from pollution and
illegal occupation and increase the treatment plant for surface water to supply
as demand .
 Rainwater harvesting should be introduced at a massive scale to ensure supply of
drinking water to the households who still have no piped connection.
 Sense of ownership is crucial to manage water supply sustainably. Active
participation of key stakeholders i.e.
officials, representatives, individuals, community people etc. should be ensured at
all levels of planning, implementation, regulation, monitoring, and evaluation of
water supply scenario.
 Sewerage treatment system should be more efficient so that effluents do not
pollute their destination.
 New technologies should be incorporated to improve the quality and efficiency of
surface water treatment plants (SWTPs).
 Proper awareness campaign through print and electronic media should be
carried out to inform and to aware people regarding „right to water‟ and the
reduction of the misuse of water.

Basic idea of Rainwater Harvesting
Rainwater harvesting, in
its broadest sense, is a
technology used for
collecting and storing
rainwater for human use
from rooftops, land
surfaces or rock
catchments using simple
techniques such as jars
and pots as well as
engineered techniques.

RainwaterHarvestingAroundtheWorld
The concept of rainwater harvesting has
been accepted by many cities, government
agencies, societies, individuals, etc in
different countries around the world. They
have set the examples of RWH systems.
There are many success stories of RWH in
developing and developed countries of
Asia, Africa, Latin
America, USA, Japan, Germany, Singapore
and others.
A wooden water
tank in Hawaii, USA
‘Rajison’ a simple and unique rainwater
utilization facility at the community level in
Tokyo, Japan.
Thai Jar: RWH System inThailand

Rainwater Harvesting - Multiple
Benefits
 Improvement in the quality of ground water
 Rise in the water levels in wells and bore wells that are
 Drying up
 Mitigation of the effects of drought and attainment of
drought proofing
 An ideal solution to water problems in areas having
inadequate water resources
 Reduction in the soil erosion as the surface runoff is reduced
 Decrease in the choking of storm water drains and flooding
of roads
 Saving of energy, to lift ground water. (One-meter rise in
water level saves 0.40-kilowatt hour of electricity)

Rainwater Harvestingbasicelements:
Typically, a rainwater harvesting system consists
of three basic elements:
 The collection system : Collection systems can vary
from simple types within a household to bigger systems
where a large catchment area contributes to an impounding
reservoir from which water is either gravitated or pumped
to water treatment plants.
 The conveyance system : Conveyance systems are
required to transfer the rainwater collected on catchment
surfaces (e.g. rooftops) to the storage tanks .
 The storage system : Storage tanks for collecting
rainwater may be located either above or below the
ground.

ComponentsofaRainwaterHarvestingSystem
All rainwater-harvesting systems
comprise six basic components
irrespective of the size of the system.
1. Catchment area/roof
2. Gutters and downspouts
3. Leaf screens and roof washers
4. Cisterns or storage tanks
5. Conveying
6. Water treatment.

Catchment Surface
The catchment area of a water harvesting system is
the surface, which receives rainfall directly and
contributes the water to the system.
It can be a paved area like a terrace or courtyard of a
building, or an unpaved area like a lawn or open
ground.
For in house uses, rooftop harvested rainwater is safer
for drinking purposes than the runoff harvested water.

Storing Rainwater or Recharging
Ground Water Aquifers
Rainwater can be
stored for direct use or
alternatively it can be
charged into the ground
water aquifers. This can
be done through any
suitable structures like
dug wells, bore
wells, recharge trenches
and recharge pits.

Filters
The types of treatment units
most commonly used by
rainwater systems are filters that
remove sediment, in consort with
either ultraviolet light or
chemical disinfection.
Filters
A filter is an important part of
the inflow structure of a RWH
System. Once screens and roof
washers remove large
debris, other filters are available
which help improve rainwater
quality.
 Gravity Based Filter
 Sand Filters
 Pressure Based Filter

From Where We Can Harvest Rainwater
Rainwater can be
harvested from the
following surfaces:
 Rooftops: If buildings
with impervious roofs are
already in place, the
catchment area is
effectively available free
of charge and they
provide a supply at the
point of consumption.

 Paved and unpaved areas:
landscapes, open
fields, parks, storm water
drains, roads and
pavements and other open
areas can be effectively
used to harvest the runoff.
The main advantage in
using ground as a
collecting surface is that
water can be collected
from a larger area. This is
particularly advantageous

 Water bodies: The
potential of water bodies
such as lakes, tanks and
ponds to store rainwater
is immense. The
harvested rainwater can
be used not only to meet
water requirements of
the city; it also
recharges ground water
aquifers.

QualityConsiderationsinUtilizingRainwater
It is generally believed that rainwater can
provide clean, safe and reliable water which
can be consumed without pre-treatment. This
however may be used in some areas that are
relatively unpolluted. Rainwater collected in
many locations contains impurities.
Therefore, in order to ensure quality of
water, the collection systems will have to be
properly built and maintained and the water
shall also have to be treated appropriately
for intended uses.

Lets
Introduce
A Sample Design Of Rainwater
Harvesting system

PlanViewof Design
Catchment
area
Gutter
Discharge
Pipe
Sedimentation
& filtration
Chamber
Dark & Close
StorageTank

Design Data
 City: Dhaka, Bangladesh
 Rainfall Intensity : 2540mm annually(last 10 years )
 Building Type: Residential (2 storied)
 Number of people :18
 Catchment Area: 2400 ft2 = 223 m2
 Runoff Coefficient : 0.8
 Storage Factor : 0.5
 Pipe Dia= 9 inch
 Filtration material : Local sand and Gravel (Recommended size)
 & Filter paper

DailyDemand
 Amount of water used for different Household activities
(Activities Per capita consumption per day)
 Bathing =18.9 liter
 Drinking = 2.5 liter
 Personal hygiene =2.9 liter
 Kitchen =8.4 liter
 washing clothes =27.7 liter
 Toileting =6.7 liter
 Cleaning Houses=12.1 liter
 Others =4.0 liter
 For all purposes = 83.2 lpcd

Available Rainwater
 Q=CIA
 =0.8*2540*10^-4*223
 = 453 m3/yr
 Loss (for flashing first water and others)
 = 53 m3/yr
 FinalAvailable Rainwater = 400 m3/yr
 or, q= 60lpcd
**Here we use rain water except Bathing ,Drinking &
Personal hygiene. For more rain water we have to increase
catchment area.

StorageTankDesign
Volume V =0.365*18*60*.5=197.1 m3
=2121 cft
(Length*wide*depth) =(16*15*9)cft

Cost
 For installing this type of rain
water harvesting system total
costing is 75000 to 80000 taka.

Sourceof data:
 Source of data:
1. Domestic water consumption patterns in a village in Bangladesh
-by M. Al – Amin & K. Mahmud
Islamic University of Technology, Gazipur, Bangladesh
S. Hosen
Dhaka WASA, Dhaka, Bangladesh
M. Akhsanul Islam
Public Works Department, Dhaka, Bangladesh
2. Water supply & sanitation By Md. Feroze Ahmed and Md. Mujibar
Rahman
3. Bangladesh Meteorological Department , Bangladesh.
4. Water supply of Dhaka city: murky future the issue of access and
inequality
by A.F.M Azim Uddin Mohammed & Abdul Baten
5. MIST Rainwater harvesting project.

MIST Rainwater Harvesting Project.

Rainwater harvesting

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