| Construction of Circular
Rainwater Cisterns Using Metal FormsElizabeth Szilassy Agência dos Correios 55.140-000 Tacaimbó PE Brasil E-mail: tacaimbo@netstage.com.br
Abstract Technical volunteers of the Mennonite Central Committee (MCC), a Non-Governmental Organisation sponsored by the Mennonite churches of North America, have worked in the semiarid region of Northeast Brazil since 1968. In the late 1970’s, they developed forms and a process for the construction of concrete cisterns as an appropriate technology for the catchment and storage of rainwater. The easy to use technology has been used to construct over 2,000 cisterns and line many hand-dug wells. There is no need for a professional mason or engineer to oversee the work; thus it is perfect for communities to use on their own. The capacity of a 6 tube (ring) circular cistern is 15.000 L of potable rainwater, collected from rural buildings using eavestroughing. This amount is enough to supply a family of 8 for 250 days using 7.5 L per person per day. The advantage of this technology is that the force of the water is equal on the wall, unlike that of a rectangular cistern, where the water force is greater on the corners, often causing leaks. The construction of these cisterns uses a set of dismountable metal moulds which have a height of 50 cm, a diameter of 2.5 m and leave a wall spacing of 8 cm. The construction time period is seven days. The material costs are approximately US$ 250.00, which may be entirely supplied by the family, or partly subsidised. The labour for the cisterns is supplied by the families, using the work bee method where 2 to 3 families construct one family’s cistern, and then together construct the next family’s cistern using the same form, which is passed from house to house. This results in the family feeling a higher degree of ownership and responsibility for the cistern. |
