Rainwater Harvesting
By Dr. Jessica Calfoforo Salas
on behalf of International Rainwater Catchment Systems Association (IRCSA)
www.ircsa.org
- kspfi@skyinet.netDescription of Initiative:
Rainwater Harvesting is a popular term used for a tradition of collecting rainwater, improved
by modern concepts and technologies, a result of more than two decades of research work
around the globe. Today, Rainwater Harvesting is used in wet and dry countries, in poor and
modern situations, for water supply and for sanitation in homes. It is utilized in addressing
agricultural productivity and food security for poverty alleviation, even in places with 200
mm of rain. Rainwater Harvesting is employed in flood mitigation in rain-drenched countries,
and in solving infiltration problems of sealed surfaces in urban areas and industrial
complexes, or in avoiding polluted water and toxic ground water.
Most of all, Rainwater Harvesting, or RWH is environmentally sound as it assists in
recharging ground water, enhances wetlands, assists forest conservation, encourages
ecological farming, and slows down construction of new dams for water supply thus helping
the ecological flow.
Discussions during the 3
rd World Water Forum session on Rainwater Harvesting aresummarized below:
1. On Water Supply and Sanitation
•
In the face of water scarcity, another major option for water supply should beconsidered at par with surface water and ground water. This third option is Rainwater
Harvesting. In some areas of the world, rainwater could be the only option. This was
shown by cases presented from Africa, South Asia, and the arid and semi-arid regions
of Brazil, Nepal, Sri Lanka, Thailand, and others.
•
Rainwater quality can be improved to WHO standards with proper monitoring andmaintenance, and by using improved technologies. In South Australia, 42% of the
population drink rainwater and only 40% drink from the main water supply.
•
In view of the above, the Forum recommended that RWH should be recognized by theUnited Nations as a major option for water supply for health and sanitation.
Governments should issue guidelines and policies for water quality monitoring and
use of improved technology. A mix of technologies is appropriate in many situations.
2. On Water and Poverty Alleviation
•
China reported that 5 million people relying on 300-400 mm annual rainfall werebenefited significantly by the practice of RWH. Additional examples were presented
from India. Forum participants agreed that rainwater harvesting is a cost effective
means to irrigate farms. It controls erosion, conditions soil, helps recharge ground
water and beneficially modifies farming practices.
•
The participants recommended that RWH should be recognized as a basic strategy forpoverty alleviation. Governments should invest in RWH facilities.
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3. On Urban Use
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Many mega-cities suffer from problems brought about by increased water demand,intense pollution and the absence of an efficient drainage system.
•
In Tokyo, RWH was advocated for water supply and disaster preparedness andmitigation.
•
In Bangladesh, 80 million people could have been affected by arsenic poisoning fromground water, if not for the implementation of RWH.
•
The problem of flooding in cities could be mitigated by RWH using low-impact runoffretardation. The Water Resource Bureau of Taiwan reports the effectiveness and the
technology of such use.
•
In Germany, 50,000 new RWH systems are installed every year to add to an existing500,000 systems, as reported by RWH equipment manufacturers.
Mainstreaming/ Sustainability
Introducing rainwater harvesting in the country’s policy often starts with an information
campaign about the new concepts and technologies and good practices around the world.
When acceptability is seen, an ordinance is passed requiring all building constructions to
include RWH facilities. Incentives such as tax rebates are offered if the owner adds a RWH
system to an existing building. These practices are found in Texas, Hawaii, Caribbean
islands, Australia, Germany and other European countries. Guidelines are issued and made
accessible to the public. Water quality monitoring guidelines are also issued. In one province
in the Philippines, a revolving fund was started to enable households to install their own
RWH facilities. In another province, a water concessionaire leads a RWH campaign as its
means of expanding its water installations. In Kenya, the women contribute some amount
every week to allow one RWH per member
The financial cost of rainwater varies across the globe, but it is invariably lower than the
alternatives. For example, in Lebanon it is $0.05 to $0.30 per m
3 of collected water, inRajasthan, India, it is $0.02 to $0.06 per liter. Essentially, the cost varies depending on the
expenditure needed for construction of the system. In Bangladesh it is $0.02 per liter of
water, and in Malaysia it is approximately $0.65 per m
3 of water, while in Thailand, theconstruction cost is $20/ 2m
3 jar. In the Philippines it is $0.05/ liter , and in Africa it is in theregion of $0.09 per stored liter of water, including labor costs.
Replicating the Initiative
The International Rainwater Catchment Systems Association (IRCSA) has documented,
through its 11 biennial international conferences, country experiences showing replications,
variations and patterns of rainwater catchment systems as adapted to specific conditions in 8
IRCSA regions of the world. .
During the development years, IRCSA members-- volunteer scientists and development
practitioners, were so focused with their studies and action researches, that promotion has
been relegated to the background. However, it could be said that the proper time has come,
since the world is experiencing water scarcity and environmental degradation. Rainwater
Catchment Systems or Rainwater Harvesting technologies are appropriate for the prevailing
conditions and are ready for the world