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Sand Dams: A Practical & Technical Manual
Abstract and Figures
Sand Dams* are a fantastic water resource solution in drylands. However, they are not appropriate everywhere. This manual describes the process of establishing the feasibility of sand dams on a regional basis whilst also detailing other solutions suitable for seasonal rivers. The manual covers the processes and practices for specific siting, designing, building and maintenance of sand dams. It is aimed at NGO and government technical and programme management staff working in drylands who are interested in understanding more and/or implementing sand dam technology; and also researchers interested in sand dams and other seasonal rivers solutions, as well as geology, hyrdogeology and hydrology. *Note: Also known as Sand Storage Dams, Sub-surface Dams, Groundwater Dams, Check Dams, Aquifer Recharge Dams; technically speaking broad-crested, contracted rectangular weir, gravity dams. The manual draws upon the knowledge of Excellent Development, ASDF and their partners in building over 1,000 sand dams and experience gained in Kenya, Zimbabwe, Mozambique, Swaziland, Uganda, Sudan and Rajasthan, India. Successfully building sand dams is not an easy task, but it is based on a small number of very simple principles and rules. Consequently, you do not need to be a qualified engineer to site, design and build a robust, effective sand dam. Technically speaking, sand dams are [rectangular weir] overflow gravity dams, constructed with steel reinforced rubble stone masonry. Experience has shown us that the building and design do not necessarily follow all the rules laid out in many technical and engineering manuals. The manual attempts to balance the need for technical explanations with simple principles and practical rules and processes. What is critical to understand for designing sand dams is that it is an art as well as a science and that understanding how seasonal rivers flow is the only way to design a successful dam. This depends on local knowledge and experience as sand dams can’t just be designed in offices by experts, nor by pure calculation. The key to success, and challenge, lies in community engagement as this is critical to correct design and sustainability. Experience tells us that the success requires engagement with a formal civil society group who own the sand dam and their involvement with end-users to place them at the heart of the decision-making processes. How this works may vary but success relies on local knowledge and the correct application and/or adaptation of sand dam technology. Chapter 2 introduces sand dams, their history and their benefits and impacts in relation to the SDGs. Chapter 3 provides guidance on regional technical feasibility of sand dams and the importance of sediment profiles. Chapter 4 describes a structured approach to introducing sand dam technology transfer into a new region. Chapter 5 is a guide to community engagement to assess the current water access, availability and quality from different technologies and establishing the community needs and priorities with key stakeholder groups. Chapter 6 is a step-by-step guide to the pre-design activities including specific siting of sand dams and abstraction options. Chapter 7 details a structured approach to designing sand dams in different environments. Chapter 8 offers guidance on procurement of materials and other vital pre-construction activities like legal agreements. Chapter 9 is a step-by-step guide to the principles and practices for the construction of sand dams Chapter 10 describes how to manage, maintain and repair sand dams. Chapter 11 describes and compares alternative water technologies used in rural drylands Appendices contain useful forms and checklists supporting the process of siting, design and construction of sand dams.
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