Hydraulic ram pumps and Sling Pumps

which has not been mentioned in any other publication. Only a careful screening of river sand anduniform mixing will result in waterproof structures. The nit is an equally important coat oftenforgotten, and the necessity of curing cannot be overemphasized. An article by Kiran Mukerji in"Trialog" describes his experiences in India with the construction of a rainwater reservoir. He hadchosen an interesting two leaf structure combining the ferro-cement technique with air-dried claybricks, using the latter as permanent shuttering. He stresses the need for professional artisans andlimits the possibilities for self-help construction. Having worked for seven years in different Africancountries, I can confirm that this reflects my own experience, and leads me to comment onappropriate technology. This term is often misunderstood for different reasons. The first is that toomany academics from developing countries have been educated in the western industrialized world.Because of their academic orientation, they have little practical technical knowledge. They considerappropriate technology to be a second-class technology invented by the industrialized north, goodenough for the poor south. More often than not they prefer to discard traditional technicalknowledge. A second reason is that some aid organizations have indirectly supported thesearguments by allowing their engineers sent to developing countries to use techniques which are notappropriate to the economical, technical and social background of these countries. The windmilldesigned and manufactured for borehole pumps will not replace the diesel pump if it costs 20 timesmore than the latter as long as cheap fuel is available at all times. The plough which ismanufactured from scrap has the advantages of being labour-intensive and recycling material, butits success is only assured if a comparable industrial product is not available. This means thatappropriate technology must first of all be a technology which is based on a cost-benefit analysis.Secondly it is difficult to create a motivation, which is needed to achieve the acceptance of any newtechnique. It is therefore of fundamental importance that the manufactured product works properly.Techniques which function poorly or not at all result in frustration, demotivation and resignation, andfor many years people will be reluctant to accept any change. The consequence of this must be thatappropriate technology also requires professional engineering. According to my experience it ismore appropriate to train and instruct a contractor and his already qualified craftsmen than to useunskilled labour in self-help construction projects without professional supervision. In constructionwork there are many jobs which can be done by unskilled labour, but substituting casual labour fortrained plasterers should not be tried.This manual offers advice on a more professional approach towards rainwater catchment and theconstruction of different types of reservoirs. It also offers a selection of the most appropriatereservoir types and gives technical advice for the construction work. As far as possible it has beenkept on a level which would allow an experienced bricklayer to use the information or a buildingtechnician acting as Clerk of Works or Supervisor to advise bricklayers and plasterers on the site. Itis not suitable for laymen in the construction field. Just as it is not possible to learn the technique ofbricklaying by reading a book, it is not possible to write a construction manual imparting all theknowledge needed for people without the practical experience in the construction field.Finally I wish to thank Karin Bell who did the illustrations and Siggi Gross who took the photographs.Special thanks go to my colleague Frederick McKelton who corrected the manuscipt.Rolf Hasse2