» Technology Profiles
» Standardized Roof Rainwater Harvesting (RWH) Technology
Description and Characterization of Technology
Roof rainwater harvesting (RWH) is the capturing of rainfall from roof surfaces and storing the collected water for use in households, schools and other private and public institutions.  RWH systems can be constructed in a multitude of ways. However, the standardized systems have been developed to provide water of good quality after days, weeks and months of storage required between rains and to be environmentally, economically and socially sustainable over time. The technology has been designed based on standardized criteria that offer affordable, appropriate, and cost-effective RWH solutions, including water filtration and disinfection, for safe urban, peri-urban and rural water supply. 


Standardization included selection and specification of the sizes and quality of the materials for rain collectors (roof and rain gutters), down pipes and other piping components, storage tanks, cleaning and disinfection methods and materials and water abstraction or distribution components.
How the technology works
RWH systems consist of various components that collect, clean, convey, store, disinfect and distribute rainwater in a house or building. The water is collected from suitable roofs, carried to rain gutters attached to the roof and cleaned before entry into downpipes by removal of leaves and other debris through the use of rain heads and diversion of part of the collected water through a first flush system to discard the dirty water from the first rains. The harvested water is then conveyed to storage tanks through downpipes and other piping system and distributed in buildings through the use of pumps, overhead tanks and plumbing networks.  Before distribution, however, the water can be further cleaned through filtration to remove suspended particles. The water can also be disinfected to render it potable. The size of the storage tank depends on how much rainwater can be collected from a given roof and the consumption rate and pattern of users.
The standardized RWH systems that have been developed are implemented in 3 main categories – the Basic, Intermediate and Advanced systems.  The Basic system is a low cost one with no filtration, distribution and disinfection components.  Water from such system is accessed by abstracting manually and directly from the storage tank.  The Intermediate system has both filtration and distribution components, including an electric pump and overhead tank, but have no disinfection.  The advanced system is a high end system in terms of both system cost and features.  It has all the functions of the intermediate system and also uses a UV disinfection component so potable water can be obtained.  All systems are fitted with rain heads and automatic first flush diverters.  The standardized systems can be modified by adding extra components as required.
 
Market Potential
    The systems have been designed to use components available in the Ghanaian market.
    They are cost effective, affordable and environmentally friendly
    They are suitable for areas with unreliable or no water supply from the utility company
    They can supply up to 80% of the annual water requirements of a household, depending on the roof catchment size, the size of the household and the consumption rate.
    The expertise to undertake good quality installations, including trained artisans with registered businesses, is available in the country
    RWH is an appropriate and recommended adaption technology at the household level for the impacts of climate change on water resources of the country.
    RWH is currently being actively promoted by government through the Ministry of Water Resources, Works and Housing.  The ministry has already developed a RWH strategy for the country. 
    RWH is currently being undertaken in various forms in some households, schools and public buildings nationwide
    Technical support for the assessment, installation and monitoring of the standardized systems is readily available at the CSIR-WRI
 
Challenges and Opportunities
The main challenge is the relatively high initial or installation cost.  Though the systems have been found to perform very well with users saving considerably from costs of water tanker services, the initial cost are high with respect to monthly incomes of the average civil servant.  The opportunity thus exists for the private sector to be involved in the diffusion of the technology through the provision of affordable loan facilities (such as the Green Loans of ProCredit) to potential beneficiaries of the technology.
Another challenge is the lack of awareness of RWH as a very good source of water to at least supplement other sources. Public education on this will, therefore, be necessary with the media playing a big role. In addition, if RWH systems are installed at ALL the CSIR institutes for demonstration purposes it will go a long way to popularizing the technology. 
 
Collaboration and Funding
The standardized systems were developed, tested and evaluated in selected households and public buildings in collaboration with CSIR-STEPRI and SINTEF of Norway.  A core of artisans also participated in several classrooms and field training sessions on RWH system installation and business development. The project was funded by the Nordic Climate Facility (NCF) of the Nordic Development Fund (NDF), implemented through NEFCO.
 
Dissemination Strategies and Diffusion
Diffusion of the technology is undertaken directly through seminars, workshops and field demonstrations with a wide variety of stakeholders including:
    Real Estate developers such as GREDA
    Ghana Water Company Ltd (GWCL) and Community Water and Sanitation Agency (CWSA)
    Selected households within GAMA
    Selected mushroom and other vegetable farmers within GAMA
    Selected schools within GAMA
    System component suppliers
    The Ministry of Education, Ministry of Environment, Science, Technology and Innovation and the Ministry of Water Resources, Works and Housing.  The print and broadcast media.
 
End-Users of the Technology
    Individual households
    Communities
    Schools, including community day schools
    Small scale mushroom and other vegetable farmers
Public and private institutions such as ministries, clinics, offices

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