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10th International Rainwater Catchment Systems Conference
"Rainwater International 2001"
Mannheim, Germany - September 2001

Section 3: Rainwater: Quality Issues

Paper 3.2

Towards Water Quality Guidance for Collected Rainwater

Han Heijnen
Environmental Health Advisor
WHO Bangladesh
GPO Box 250
Dhaka 1000
Bangladesh
e-mail: whosani@citechco.net

Introduction

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 option.

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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