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

Moderator's Summaries of Discussion in Sessions

B1: Rainwater Harvesting in an Urban Context
Terry Thomas

The Urban Stream comprised contributions from several continents and complemented the mainly urban papers in the parallel fbr/ European conference. In those contributions, most papers linked RWH with drainage, aquifer replenishment or architectural 'greening' rather than with domestic water supply. Several industrial and developing countries are suffering from falling or polluted aquifers for which problem injecting runoff water through wells assist (other countries have instead a problem with rising aquifers that such injection would only exacerbate).

There was little discussion of affordability, especially in a developing country context, and the contrast between industrialized-country system budgets of over 3000 Euro per household and the system budget ceilings likely to apply in tropical cities (under 150 Euro) was striking. The urban sessions also did not directly address water quality, but it was clear that in Europe urban roof water is unlikely to be used for drinking whereas in developing cities it is potentially the cleanest water available to dwellers in slums or in peri-urban areas.

Some special niches were identified as being available to immediate occupation by RWH. These included industrial water supply in areas reaching the limits of the surface or groundwater supply and domestic supply in those suburban areas or rapidly-growing cities not yet served by heavily subsidized piped water. RWH was shown to have the potential to reduce the costs of drainage provision in new housing estates and to significantly improve the ecology of large urban institutional sites.

In developed countries, urban RWH expansion is being driven by professionals like architects. In the cities of less developed countries the process is hampered by householder ignorance and their difficulty in finding competent installers. 'Informal' (spontaneous) DRWH in such cities is thought to be widely practiced but was not discussed. It was generally felt however that supplies from conventional water sources are unlikely to be able to keep up the rapidly growing populations of cities in poorer countries.

B2: Rainwater Catchment (RWC) in Humid and Arid Regions (HARs)
Johann Gnadlinger / Tanuja Ariyananda

 Most of the previous IRCS Conferences took place in HARs where RWC was invented thousand of years ago. The poster sessions and presentations showed experiences of RWC in the HARs also in the German conference: they showed many successful projects and experiences worldwide.

Special discussion points and topics:

  • Mostly RWC for domestic purposes 
  • The value and price of water is discussed worldwide: valuing rainwater also 
  • Participatory / holistic approach: communities, women, the poor, nature 
  • Social, economic and health benefits of RWC 
  • Operation and maintenance of RWCS is cheaper than other systems


  • Funding of projects by NGOs or/and by government 
  • Managed totally by the communities  
  • Governmental commitments 
  • Rain water collection is just not roof water collection (Subsurface dams, courtyard collection, rainwater use for livestock, etc.) 
  • What type and size fits best for the people (it depends on climate, people, economy, etc.)

Further discussion is needed as regards:

  • RWC and water supply security 
  • RWC modeling 
  • Multiple sourcing of water supply (rain water harvesting as partial source)
  • Economic valuation of RWC 
  • Involvement other than English speaking people (French, Spanish, Portuguese,...)

B3: Water Quality of Harvested Rainwater (for Drinking)
Jayne Heyworth

The overall theme of the water quality sessions was " towards a health risk assessment of harvested rainwater". The series of presentations contributed data on various aspects of Health Risk Assessment including: Bacteriological risks, chemical risks and victor-borne diseases.

The key questions that guided the three water quality sessions were:

  • What data inputs do we need for a health risk assessment of harvested water quality? 
  • What do we know now? 
  • What are the gaps in data?

Lessons learnt:

  • Guidelines on harvested rainwater quality are needed from World Health Organization and to assist people in following a risk-assessment approach. However these guidelines should focus on the process rather than be misused as standards. Social and political considerations are needed in undertaking a risk assessment approach. 
  • Hazard Analysis and Critical Control Points (HACCP) as used in the food industry offers a methodology to guide us on process of risk assessment , and the potential to avoid or reduce risks associated with harvesting rainwater. A Sanitary survey and process monitoring is recommended in this respect. 
  • No one risk assessment will be adequate as each site may be associated with different risk. Hence the process is important rather than pass-fail standards. Caution should be taken to ensure to assess site- specific risks and take the appropriate mitigation measures. 
  • Guidelines for Domestic Rain Water Harvesting should describe good practice in design and maintenance of the system. Bacteriological testing is obviously useful in the context of research, but it has limited use for monitoring. 
  • In one study, epidemiological research showed that children taking rainwater have 32% less chance of having a gastro-enteric episode than those using public piped water in South Australia. This type of research is very useful for policy development and should be undertaken elsewhere as well. 
  • Chemical quality of roof water, especially lead, cadmium, zinc and pesticides needs to be considered but should be done to check once in a while and only when one suspects chemical contamination due to human settlement, industrial or agricultural activities. 
  • Vector borne diseases are a risk in rainwater harvesting in certain climatic zones and needs to be carefully considered in rainwater harvesting programs. 
  • For final treatment of rainwater, Solar Disinfection (SODIS) and appropriate filters can be considered to make the water finally fit for drinking.

B4: Water Harvesting for Agriculture, Including Environmental Aspects
Andrew Lo

There were altogether 26 papers (both oral and poster) presented in the B4 session. The major discussion points touched upon topics such as:

  • Selection of appropriate rainwater harvesting techniques in arid and semi-arid areas 
  • Efficiency of plant barriers on runoff reduction 
  • The best catchment surface materials for rainwater harvesting 
  • Rainwater harvesting as supplemental irrigation in agricultural production 
  • Rainwater harvesting to improve crop yield and food security 
  • Improvement of quality of stored rainwater using natural energies 
  • Environmental benefits of rainwater harvesting for reducing groundwater withdrawal

The major lessons learnt from the case studies and paper presentations are as follows:

  • With the global change affecting the rainfall pattern all over the world, the storage component of rainwater harvesting is becoming a critical design issue in the future. 
  • The precious rainwater collected needs to be used more efficiently and effectively. 
  • Remote sensing, as well as field data is essential in modeling rainwater harvesting design and planning. 
  • Economic and risk analyses are necessary to evaluate performance of rainwater harvesting systems. 

B5: Policy Issues and Awareness Raising
Jessica Salas

Basic Considerations on the techniques, ideas, processes to promote rainwater harvesting included:

    1. The Promotion of the multi-use of rainwater. 
    2. In promoting rainwater for drinking, improve quality with WHO guidelines/ standards

A Two-pronged approach to rainwater promotion:

    1. Economic mainstreaming - As the rainwater technologies get mature and accepted, both socially and economically, the business sector picks up the opportunity of adding value to these technologies by putting them out in the market. In some countries, communities are ready for economic mainstreaming. In this case, the conference suggests: product differentiation to reflect multi-use of rainwater and increase customers' choice, segmentize the market to make rainwater technologies adapt to local conditions. 
    2. Political support - The second approach particularly needed in developing countries is political support. This means rallying the local government, the national government to lead rainwater utilization through policy support and investment in public funds. Promoting rainwater in this manner will be easier with community-based project implementation, use of mass media, identifying local partners, and accounting for community costs.

In implementing these two approaches, care should be taken to estimate and monitor the impact on equity. Influential businesses could sabotage community efforts when the two approaches collide. Local government policies, directed by stakeholders should be able to protect the community to enjoy their water rights.


Presenters and participants gave examples of the laws involving rainwater and their implication to rainwater promotion. A summary is as follows:

    1. Rainwater is not even mentioned in water laws. 
    2. There are countries where rainwater belongs to the government. Extra permits are required for rainwater harvesting. Rainwater is not seen as a water supply option. It is not seen as an individual human right. 
    3. In some countries, there is a growing trend of decentralization. Right to access water is decentralized to the community although ownership belongs to the state. 
    4. The enabling policy environment shows genuine interest in conservation and reuse of water.  
      1. Water law gives tax exemption to rainwater harvesting equipment, supplies or activities. No property tax is imposed on these equipment. 
      2. Water laws offer incentives in form of rebates if a taxpayer puts up his/her own rainwater tank 
      3. Other governments provide rainwater incentive by facilitating financing of the rainwater tank or rainwater system. 
      4. In Australia, rainwater is required in all public housing projects.

In a different perspective, an issue was raised that the government has a policy not to harvest rain in a particular place because another community is deprived. This leads to the perspective of upstream-downstream conflict that could only be resolved when the perspective of the basin or the watershed, or the natural rainwater catchment system is seen. This could lead to a policy advocacy for a catchment basin management or the natural catchment, even in dealing with rainwater harvesting. It is recommended that his concern be taken up in future conferences of IRCSA.

The Final Discussion

Topics, Contributions, Proceedings

Success stories are needed to be collected

  • "More emphasis on socio-political background in DCs" 
  • "More emphasis on regional (appropriate) technical aspects" 
  • "For a rwh-push in Africa there's a need for more emphasis on community management, management of water resources, technical aspects" 
  • "training of trainers is important and has to be addressed"

the Question of Standards

  • "adopt German experiences as standards.. ?" 
  • "..or international ones ?" 
  • "we cannot have just one common standard for all, people need a choice, there are gaps between the countries"

More powerful and practical recommendations/an agenda / one vision and a common ground till Kyoto 2003 - what are we going to present there ?

  • "success stories need to be systemized" 
  • "an international organisation should publish a commitment" 
  • "we need links with international organisations like Int Ass for Water Quality, Int. Ass for storm drainage" 
  • "the voice of IRCSA is needed ("you are only heard, when you are in the political centre") 
  • "need for clear and common definitions, there still is confusion about the word rwh" 
  • "we need to come from rw-harvesting to rw-management"

Which form of further communication for rwh ?

  • "using the internet as medium for communication" 
  • "activities of the members need to be written down" 
  • "cse is starting a e-newsletter on rwh" 
  • "what about a rwh-journal ?" 
  • "and a rwh cd-rom ?" 
  • "all previous rainwater conferences need to be on the net" 
  • "establishment of a Forum for RW Technology Transfer ?"

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