Water from Small Dams

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6.9 An example of a complete designThe Kimuu Valley Dam described in this handbook.44
Chapter 7.Construction of a valley dam7.1 Check list before starting construction workBefore construction work begins it is important to check that the following criteria havebeen met and relevant procedures followed according to the sequence listed below:1) A suitable site for the dam has been identified and its feasibility investigated interms of the issues highlighted in Chapter 2.2) A written agreement on the ownership of the dam site, an access road, usage ofwater <strong>from</strong> the dam and conservation of the catchment has been completed.3) Design drawings and bill of quantities for the dam are ready.4) A decision regarding the method of excavation of soil works whether manual labour,draught power or machinery. Quotations for purchases and hiring of labour ormachinery or prior agreement with community regarding free labour inputs.5) Any legal requirements have been addressed.6) Funds for survey, design and construction of the dam have been secured.7) Construction of valley dams should only be done during dry seasons where there isvery little risk of heavy rainfall because a dam under construction can easily beswept away by a thunderstorm or heavy shower.7.2 The keyThe key under the dam wall prevents water <strong>from</strong> seeping through layers of sand orsandy soil under a dam wall. The two ends of a key should extend to the maximum levelof water in a reservoir.Place two pegs at both ends of the lowernylon string to show the width of the key,which should have a width of 2.5 metres.Attach a nylon string between these 4 pegsto mark the full extent of the key.When a key has been excavated to a depthof 60 cm below any layer of sand or sandysoil, the vertical sides of the key are cut toa slope of 45 degrees for stabilising theexcavation.45
Page 1 and 2: Water from Small DamsA handbook for
Page 3 and 4: ContentsAcknowledgement ………
Page 5 and 6: AcknowledgmentsMuch gratitude is du
Page 7 and 8: TECHNICAL VOCABULARYASAL = Arid and
Page 9 and 10: Chapter 1.Introduction to small dam
Page 11 and 12: Borrow pits, also called murram pit
Page 13 and 14: Rock catchment dams can either bebu
Page 15 and 16: Chapter 2.Considerations before con
Page 17: It is difficult to estimate the wat
Page 21 and 22: If the answers to the questions lis
Page 23 and 24: 3.3 OwnershipValley dams are normal
Page 25 and 26: Chapter 4.Charco damsFarmers and ca
Page 27 and 28: Since there are no documented guide
Page 29 and 30: 4.4 ConstructionThe construction si
Page 31 and 32: Simple equipment for measuring leve
Page 33 and 34: Another very positive feature of hi
Page 35 and 36: For manual excavation, divide the a
Page 37 and 38: A hillside dam built by a tractorpl
Page 39 and 40: The rainwater runoff from the catch
Page 41 and 42: 6.4 Measurements to be taken of a d
Page 43 and 44: The sketch shows that a freeboard 1
Page 45: Homogeneous dam walls can be built
Page 48 and 49: 6.8 Bill of Quantities (BQ) and cos
Page 50 and 51: The table below shows all the tools
Page 54 and 55: It is a good idea to have an experi
Page 56 and 57: Water drawn directly from a dam res
Page 58 and 59: Usually, soil for building the side
Page 60 and 61: The usual types of pit latrines wit
Page 62 and 63: Silt traps made of vegetation plant
Page 64 and 65: 9.2 Washed-out dam wallsThere are s
Page 66: ReferencesBrown, L.N. 1965. Small e

Water from Small Dams

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