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About UNEP
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United Nations Environment Programme
Division of Technology, Industry and Economics
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Newsletter and Technical Publications

Rainwater Harvesting And Utilisation

An Environmentally Sound Approach for Sustainable
Urban Water Management: An Introductory Guide for Decision-Makers


What Must be Considered When Selecting Rainwater as a Water Supply Source?

The disadvantages of the rainwater harvesting and utilisation systems are:
  The catchment area and storage capacity of a system are relatively small. There is a great variation in weather. During a prolonged drought, the storage tank may dry up.
  Maintenance of rainwater harvesting systems, and the quality of collected water, can be difficult for users.
  Extensive development of rainwater harvesting systems may reduce the income of public water systems.
  Rainwater harvesting systems are often not part of the building code and lack clear guidelines for users/developers to follow.
  Rainwater utilisation has not been recognized as an alternative of water supply system by the public sector. Governments typically do not include rainwater utilisation in their water management policies, and citizens do not demand rainwater utilisation in their communities.
  Rainwater storage tanks may be a hazard to children who play around it.
  Rainwater storage tanks may take up valuable space.
  Some development costs of larger rainwater catchment system may be too high if the costs are not shared with other systems as part of a multi-purpose network

Learning from these advantages and disadvantages, the decision to use rainwater as a new water source should be discussed among citizen/user groups and government water officials. Topics of such discussion might include:
  What are the alternatives for new water supply sources?
  What are the advantages and disadvantages of each alternative of new water source?
  How is rainwater utilisation ranked among the alternatives of new water supply sources, taking into account the viewpoints of private citizens and governmental officials?
  What are the responsibilities of users and communities for the participation in new water source development?
After these discussions, if rainwater utilisation is selected for development, then a detailed engineering feasibility study can be undertaken.
 

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