Rainwater Harvesting method,Over 70% of our Earth's surface is covered by water
More than 97% of Earth’s water is in the oceans, 2% is in ice and glaciers- (Both are unsuitable for human use because of Salinity (Ocean Water) and location (ice caps and glaciers)
The total amount of water for which all the people, plants and animals on Earth compete is much less than 1% of the total
Rainwater harvesting- Alternative water source- Technology used for collecting and storing rainwater for human use from rooftops, land surfaces
Decentralised system – Installed in houses, Institutions, community
2. NORWEGIAN
UNIVERSITY
OF
LIFE
SCIENCES
www.umb.no
Total World Water Supply
Location Water
Volume
(km3)
% of Total
Water
Oceans 1,230,000,000 97.17
Ice caps and glaciers 28,600,000 2.5
Atmosphere 12,700 0.001
Rivers and Streams 1,200 0.0001
Lakes (Fresh water) 123,000 0.009
Groundwater
(Shallow to depth of
0.8 km)
4,000,000 0.31
Department
of
Plant
and
Environmental
Sciences
Over 70% of our Earth's surface is covered by water
More than 97% of Earth’s water is in the oceans, 2% is in ice and
glaciers- (Both are unsuitable for human use because of Salinity
(Ocean Water) and location (ice caps and glaciers)
The total amount of water for which all the people, plants and animals
on Earth compete is much less than 1% of the total
5. NORWEGIAN
UNIVERSITY
OF
LIFE
SCIENCES
www.umb.no
Where rainwater harvesting is
particularly attractive ?
– Rural area with no surface water sources
– Supply from surface and groundwater sources cannot
meet the water demand (Urban area)
– Groundwater contaminated with Arsenic
– Household do not have capacity to pay for centralised
water supply system
Department
of
Plant
and
Environmental
Sciences
6. NORWEGIAN
UNIVERSITY
OF
LIFE
SCIENCES
www.umb.no
Benefit of Rainwater harvesting
Has multiple uses-
– Domestic consumption
– toilet flushing, sprinkling,
– ground water recharge,
– reduces urban storm runoff and associate flooding and
errosion
Low maintenance
Department
of
Plant
and
Environmental
Sciences
13. NORWEGIAN
UNIVERSITY
OF
LIFE
SCIENCES
www.umb.no
Storage
Storage tank, acts to flatten out any fluctuation
in rainfall and usage allowing water use to be, to
a greater or lesser extent, independent of rainfall.
Types
– Ferrocement tank - cement-rich mortar reinforced with
layers of wire mesh,
– Fiberglass
Department
of
Plant
and
Environmental
Sciences
15. NORWEGIAN
UNIVERSITY
OF
LIFE
SCIENCES
www.umb.no
Sizing of storage tank
Demand side approach
A very simple method is to calculate the largest
storage requirement based on the consumption
rates and occupancy of the building.
– Consumption per capita per day, C – 20 litres
– Number of people per household, n – 6
– Longest average dry period – 25 days
Storage requirement = C x n x 25 = 3000
litres
Department
of
Plant
and
Environmental
Sciences
16. NORWEGIAN
UNIVERSITY
OF
LIFE
SCIENCES
www.umb.no
Quality of rainwater
The quality of rainwater is relatively good but it is
not free from all impurities.
Depends upont type and condition of the
catchments and the storage tank
Dust from the soil, and droppings of birds and
animals could be the source of contamination by
the bacteria.
Department
of
Plant
and
Environmental
Sciences
17. NORWEGIAN
UNIVERSITY
OF
LIFE
SCIENCES
www.umb.no
Method to enhance quality
The first run off from the
roof should be discarded to
prevent entry of impurities
from the roof.
In case of difficulties in the
rejection of first flow-
Clean the roof and gutter at
the beginning of the rainy
season
Department
of
Plant
and
Environmental
Sciences
18. NORWEGIAN
UNIVERSITY
OF
LIFE
SCIENCES
www.umb.no
Method to enhance quality
Cleanliness of roof and storage tank is critical in
maintaining good quality of rainwater.
The storage tank requires cleaning and disinfection
when the tank is empty or at least once in a year.
Department
of
Plant
and
Environmental
Sciences
20. NORWEGIAN
UNIVERSITY
OF
LIFE
SCIENCES
www.umb.no
Disinfecting Rainwater
Rainwater can be used for drinking, if it is clear, has no
or very little taste or smell and is from well maintained
system
Rainwater may not meet WHO drinking water quality
standards, specifically microbiological quality standards,
hence some disinfection is recommended.
Disinfection can be done by:
– boiling the water in before consumption
– adding chlorine compounds/bleaching powder in
required quantity to the water stored in the tank.
– using slow sand filtration
– solar disinfection (SODIS)
Department
of
Plant
and
Environmental
Sciences
22. NORWEGIAN
UNIVERSITY
OF
LIFE
SCIENCES
www.umb.no
22
Rainwater Harvesting and Utilization. An Environmentally Sound
Approach for Sustainable Urban Water Management: An
Introductory Guide for Decision-Makers. IETC-UNEP, Japan.
Rainwater catchment systems for Household Water Supply
(1991). Environmental Sanitation Reviews No No 32. ENSIC,
Bangkok, Thailand.
UNEP-IETC (1999) Proceedings of the International Symposium
on Efficient Water Use in Urban Areas - Innovative Ways of
Finding Water for Cities. (8 to 10 June 1999), Kobe, Japan.
Gould, J. and Nissen-Petersen, E. (1999) Rainwater Catchment
Systems for Domestic Supply. IT Publications, London
Hasse, R. (1989) Rainwater Reservoirs- Above Ground Structures
for Roof Catchment. GTZ.
NGO Forum and SDC (2001) Rain Water Harvesting System.
NGO Forum for Drinking Water Supply and Sanitation and SDC,
Bangladesh.
Bibliography
Department
of
Plant
and
Environmental
Sciences
23. NORWEGIAN
UNIVERSITY
OF
LIFE
SCIENCES
www.umb.no
23
International Rainwater Catchment Systems Association
http://www.eng.warwick.ac.uk/ircsa/
American Rainwater Catchment Association
http://www.arcsa-usa.org/
Centre for Science and Environment (CSE), India
http://www.rainwaterharvesting.org
Development Technology Unit, School of Engineering,
University of Warwick, UK
http://www.eng.warwick.ac.uk/DTU/rwh/index.html
Chennai Metrowater, India
http://www.chennaimetrowater.com/rainwaterfaqs.htm
Rainwater Partnership
http://www.rainwaterpartnership.org/
Web Resources on RWH (1)
Department
of
Plant
and
Environmental
Sciences
24. NORWEGIAN
UNIVERSITY
OF
LIFE
SCIENCES
www.umb.no
24
Lanka Rainwater Harvesting Forum
http://www.rainwaterharvesting.com
International Rainwater Harvesting Alliance
http://www.irha-h2o.org/
Greater Horn of Africa Rainwater Partnership (GHARP)
http://www.gharainwater.org/
The Web of Rain
http://www.gdrc.org/uem/water/rainwater/rain-web.html
Web Resources on RWH (2)
Department
of
Plant
and
Environmental
Sciences
