International Rainwater Catchment Systems Conference
Mannheim, Germany - September 2001
Rainwater: Quality Issues
Water Quality Guidance for Collected Rainwater
Environmental Health Advisor
GPO Box 250
Traditionally surface water and (shallow) ground water
have been used as sources for drinking water. In harsher environments
societies have developed ways of securing sufficient good quality water
by developing techniques for digging deeper and collecting water in underground
drains (qanats) or by constructing run-off water collection systems to
fill surface reservoirs (tank, wewa, hafir, etc..).
In recent years exploitation of water resources has focused
on providing water for food production, and water supply for domestic
and industrial purposes. Population growth, intensification of agriculture
and growing urbanization have led to water stresses in locations that
used to self sufficient in water. Quantity and quality of water for all
human purposes are becoming compromised and many countries are now developing
strategies to conserve and protect water.
Households and communities all over the world have from
time immemorial collected rainwater for their daily needs. Dying Wisdom,
published by CSE in New Delhi in 1995 as a result of an extensive journey
across the Indian Sub-continent, beautifully describes the intricate ways
in which people secured their livelihood through harvesting and protection
of rainwater. On the other hand, public health concerns and technological
developments of the last 150 years have combined to provide many people
with safe and convenient water supply facilities near their home. This
will have pushed rainwater harvesting to the background as a water supply
Unfortunately, the Global Assessment of the Water Supply
and Sanitation Sector, 2000, has to report that in 2000 only 82% (4.9
billion) of the world's population is served with some form of improved
water supply. The diagram above shows that for the combined population
of Africa, Asia, Latin America and the Caribbean some 21% is not served.
Chances are that many of those not served, and even a good
number of those served by an improved supply, will practice some form
of rainwater harvesting to secure or augment domestic supplies.
In view of the stress on available water sources and because
many people will have no alternative, the use of rainwater for a variety
of domestic purposes is likely to grow rapidly. Not all collected rainwater
will be used for drinking and cooking. But for the part that is, it would
be useful to develop guidelines with respect to safeguarding its quality.
WHO intends to include guidance on the quality and storage of collected
rainwater as a source of drinking water, in its next update of the Drinking
Water Quality Guidelines scheduled for 2003.
PDF of full document (6pp, 50kb)
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