A Global Village
Issue 4 » Engineering Development

Harvesting Water for Tanzania

Timothy Thang, Mechanical Engineering, Imperial College London

Raincatcher Imperial is an annual student-led project that aims to improve the standard of living in Tanzania through the provision of clean drinking water. According to Tanzania’s Ministry of Water, it is estimated that 70% of the rural population have no access to safe water causing the deaths of 31,000 children due to diarrhoea each year in Tanzania alone. In remote regions even unclean water is in short supply as the dry season lasts for up to eight months of the year. Raincatcher Imperial attempts to alleviate this problem by constructing Rainwater Harvesting Systems (RHSs) for such communities.

Tanzania experiences a dry season of up to 8 months during which time there is little to no rainfall. In contrast, during the wet season, rainfall is heavy and flooding occurs. The total rainfall over the year is sufficient for the population’s water needs but is very unevenly distributed and drought is common.

Rainwater harvesting is a viable means of providing clean drinking water to the local population, as it is a simple yet effective method of storing water for countries with seasonal rainfall patterns. Through the adoption of rainwater harvesting, excess rainfall can be stored in water tanks during the wet season that may be rationed during the dry season. This allows the local population to have a constant supply of water all year round, and minimises the population’s reliance on well water during the dry season that is not only dirtier than harvested rainwater but expensive as well.

Rainwater harvesting is a
viable means of providing
clean drinking water to
the local population

Since its inaugural project, Raincatcher Imperial has been working closely with Caritas Tanzania, a Tanzanian-based NGO. Each year a number of sites in need of rainwater harvesting systems are identified by Caritas and presented to the team. The team then decides how many rainwater harvesting systems to build and where they should be built taking many factors into consideration including that of available funding. Other logistical factors such as accessibility to construction materials, the safety of the team and ease of travel are also taken into account.

Capturing the Rain
The rainwater harvesting systems that are constructed by Raincatcher Imperial are designed by a Tanzanian engineer specialising in rainwater harvesting systems in collaboration with specialists at Imperial College. A key feature of these rainwater harvesting systems includes a dome-shaped storage tank that takes advantage of the compressive strength of concrete. At the same time the dome shape minimises stress concentrations and reduces the risk of fracture in the tank. A ring beam has also been incorporated into the tanks to make them earthquake-resistant. The design has low labour and construction costs and is built underground with space considerations in mind.

When the first rains fall after the dry season, the rainwater is allowed to first run off the roof but not into the tank. This first flush system allows the initial rainfall to be used to clean the roof of dirt and debris. Once the roofs have been cleaned, the storage tank inlet pipe is then connected to the gutters of the roofs allowing water to be collected off the roofs of surrounding buildings and stored in the storage tank. The storage levels of the tanks should be managed such that the tank is full at the end of the wet season. The water in the storage tank is then further pumped up into a water tower that is connected to a tap stand.

Water for Education
For the 2010 project the tap stand is located in a shed and can only be accessed by the matron and head girl of the school for which the RHS was built. This ensures that during the dry season the water in the tank can be properly calculated and rationed to ensure that water is being consumed from the storage tank at the appropriate rate. At the end of the dry season the tank is cleaned, inspected and the cycle repeats with the new wet season. During the team’s time in Tanzania, locals will be trained to clean and inspect the tank.

Members of Raincatcher Imperial faced many challenges on the ground in Tanzania. One of the main challenges faced by teams over the years is the language barrier. Most Tanzanians speak rudimentary English and many team members have difficulty communicating. Although most team members attempt to overcome this barrier by learning basic Swahili before going to Tanzania, their extremely fundamental grasp of the language is appreciated although largely ineffectual. Another significant challenge lay in securing materials in Tanzania. In 2010, the team faced delays in construction when no cement was being supplied to the nearest large town.

Raincatcher Imperial has improved the quality of life of local communities. The availability of clean water at schools through the RHS has meant that parents are more likely to send their children to school thus reducing the chances of their children falling ill. The children spend more time at school, time which might in the past have been spent fetching water from potentially contaminated wells, and receive a better education and prospects. It has also allowed the school to accommodate more students in their dormitories.

Raincatcher Imperial boosted the local economy as all resources and materials for the construction of the tanks were purchased locally at a cost of approximately £12,000 per RHS. Local labour was also hired during the construction phase thus generating jobs for members of the local community.

Raincatcher Imperial strives to make a positive impact on the provision of clean water to the rural villages of Tanzania, and hopes to improve the quality of life for the people through the provision of environmentally sustainable and ethically sound RHSs. If you would like to know more about Raincatcher Imperial or would like to support our efforts in any way, please visit our website at www.rwh-tanzania.co.uk. 

Timothy Thang is a 3rd year undergraduate in Mechanical Engineering at Imperial College London, helping with promotion and fundraising for the Raincatcher project.

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