Hydraulic ram pumps and Sling Pumps

Rainwater Reservoirs aboveGround Structuresfor Roof Catchmentby Rolf HasseA Publication of Deutsches Zentrum fürEntwicklungstechnologien -GATEin: Deutsche Gesellschaft für TechnischeZusammenarbeit (GTZ) GmbH - 1989PrefaceThis paper was written in the Botswana village of Romotswa in 1987, the seventh year of drought inSouthern Africa. Romotswa has a history of rainwater catchment. Many of the private buildings aswell as public buildings are equipped with reservoirs, most of them dating from the time beforemunicipal water supply existed. In 1983 a large underground water source was detected here bygeologists. The yield of the drilled wells is of such magnitude that for some time in 1984, the townsof Gaborone, the capital of Botswana, and Lobatse were both supplied with water from Romotswa.During my residence in this little border village in SouthEast Botswana, 30 km away from the capital,I noticed that rainwater catchment had lost momentum as a result of the centralized water supply.Many of the catchment facilities were poorly maintained so that much of the rainwater during therare but heavy downpours was lost due to gutter leaks and/ or dislocated downpipes. At the sametime newly built schools and other public buildings had been equipped with reservoirs which weremuch too small for the huge catchment areas. It became obvious that no calculations and no designfor the systems had been made. Unprofessionally fixed gutters and downpipes were anotherproblem. It should be mentioned that drought in Botswana, as in other parts of the world's desertbelt, does not mean that no rain occurs at all. It simply means that the mean annual rainfall has notbeen reached and sometimes -just as serious - that the distribution of precipitation is extremelyunequal. In such unfavourable climatic conditions heavy downpours of up to 100 mm in one hour domore harm than good to the arable land. The water does not penetrate the very dry and hard soiland the massive runoff results in severe soil erosion. Together with my experience gained as TownArchitect in Lobatse, all these observations have influenced the structure of this paper. Originallyplanned as a technical manual for the construction of reinforced bricktanks, it became clear that theentire issue of rainwater catchment and storage should be put into a broader context. At the sametime UNICEF, Kenya, had approached the Editor with the Laurie F. Childers manual for aferro-cement tank. It was agreed that the accumulated knowledge in this paper should be used toprovide an introduction of different techniques for building rainwater reservoirs. Since thepossibilities of building rainwater reservoirs depend entirely on the availability of the requiredmaterials, it is the intention of this publication to cater for a variety of situations. N.J. Wilkinson of theBotswana Technology Centre has published a manual showing another technique of building aferro-cement tank. This technique has advantages under certain circumstances. E.H. Robinson haserected structures for "Christian Action for Development in the Caribbean" using another technique.Each of the different structures has its advantages. Which one should be chosen depends on thesituation at the specific site. Much emphasis is placed on material testing and mixing. Here theadvice given by Childers matches the experience I have made with waterproof cement plaster and