International Rainwater Catchment Systems Conference
Mannheim, Germany - September 2001
of Discussion in Sessions
B1: Rainwater Harvesting
in an Urban Context
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
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.
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,
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,...)
Quality of Harvested Rainwater (for Drinking)
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
- What do we know now?
- What are the gaps in data?
- 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
- 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
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
- 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
- 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
B5: Policy Issues
and Awareness Raising
Basic Considerations on the techniques, ideas, processes to promote rainwater
- The Promotion of the multi-use of rainwater.
- In promoting rainwater for drinking, improve quality with WHO guidelines/
A Two-pronged approach to rainwater promotion:
- 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.
- 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.
ON LEGAL FRAMEWORKS AND THEIR IMPLICATIONS TO RAINWATER PROMOTION
Presenters and participants gave examples of the laws involving rainwater and
their implication to rainwater promotion. A summary is as follows:
- Rainwater is not even mentioned in water laws.
- 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.
- In some countries, there is a growing trend of decentralization. Right to
access water is decentralized to the community although ownership belongs to the
- The enabling policy environment shows genuine interest in conservation and
reuse of water.
- Water law gives tax exemption to rainwater harvesting equipment, supplies
or activities. No property tax is imposed on these equipment.
- Water laws offer incentives in form of rebates if a taxpayer puts up his/her
own rainwater tank
- Other governments provide rainwater incentive by facilitating financing of
the rainwater tank or rainwater system.
- 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
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 ?"
for further discussion/ up-dates of on-going activities you should join
|Note: The IRCSA proceedings
section is still new and under active management, If you find any problems,
ommissions or corrections please contact
the administrator so we can put things right.