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Sand Dams: A Practical & Technical Manual

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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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... The volume of sediment stored upstream of the sand dam can be approximated using the following relationship [22,67]: ...
... Saves 30-90 min spent on collecting water [25,67]; 2. ...
... Improves the vegetation cover in the area, supply of water for livestock, wildlife, and small-scale irrigation and increases food production and income [25,49,67,80]; 3. ...
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Augmenting water availability using water-harvesting structures is of importance in arid and semi-arid regions (ASARs). This paper provides an overview and examines challenges and prospects of the sand dam application in dry riverbeds of ASARs. The technology filters and protects water from contamination and evaporation with low to no maintenance cost. Sand dams improve the socio-economy of the community and help to cope with drought and climate change. However, success depends on the site selection, design, and construction. The ideal site for a sand dam is at a transition between mountains and plains, with no bend, intermediate slope, and impermeable riverbed in a catchment with a slope greater than 2°. The spillway dimensioning considers the flow velocity, sediment properties, and storage target, and the construction is in multi-stages. Recently, the failure of several sand dams because of incorrect siting, evaporation loss, and one-stage construction were reported. Revision of practitioners’ manuals by considering catchment scale hydrological and hydrogeological characteristics, spillway height, and sediment transport are recommended. Research shows that protected wells have better water quality than open wells and scoop holes. Therefore, the community should avoid open defecation, pit latrines, tethering of animals, and applying pesticides near the sand dam.
... Sand dams are, most commonly, rectangular weir overflow gravity dams, that are built using rubble stone masonry reinforced with steel ( Figure 1) (Maddrell, 2018). These structures can, when built over a seasonal sandy riverbed, store massive volumes of water that is filtered, protected from evaporation and prevented from acting as a breeding ground from mosquitos, a water-related insect vector for disease (Lasage et al., 2013). ...
... Brazil (Barrow, 1999). In fact, sand dams have potential in all of the world's drylands, which constitute over 40 percent of the global terrestrial area and contain over a third of the world's total population (who also make up almost 75 percent of the world's poor) (Maddrell, 2018). ...
... Despite the technology existing for hundreds of years, most sand dams have been built in Kenya and in the last 25 years by a small number of NGOs and community groups with external support (Maddrell, 2018). Even then, construction and associated hydrologic research have only gained momentum at the start of the 21 st century. ...
Thesis
Community-based rainwater storage in semi-arid drylands can help to adapt to climate change and mitigate intensifying water scarcity. Sand dams are structures built in seasonal sandy rivers which store excess water upstream in deposited sand to overcome dry periods. This paper evaluates the technology’s upscaling process and the potential of a British Army involvement. For this evaluation, a thematic analysis was conducted. Data was collected by semi-structured interviews conducted with five key respondents from a variety of disciplines relevant to either the technology or the British Army. Findings underline how global upscaling is limited by a lack of understanding of critical success factors. The study identified three types of potential British Army intervention: (1) logistical support (2) the development of sand dams in regions of conflict, and (3) the restoration of sand dams following humanitarian crises. Military humanitarian assistance is restricted to response and recovery as a last resort, but it is recommended efforts are made by the British Army to develop an understanding of the technology such that it could support future upscaling if required.
... Because surface water flow only occurs when the aquifer is fully saturated (Nord, 1985;, surface water flow frequency equates to alluvial aquifer recharge frequency. Understanding of flow frequency is also required for a sand dam feasibility assessment according to Maddrell (2018): "Sand dams must be sited on a sufficiently seasonal river" (the number 1 technical pre-condition). Furthermore, because sand dams should be constructed in lifts following each surface water flow event (in order to enable passage of silts and trapping of only coarse sediment), it is important to know the flow frequency to enable project management of materials and labour (Nissen-Petersen, 2006). ...
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Ephemeral sand rivers are common throughout the world's dryland regions, often providing a water source where alternatives are unavailable. Alluvial aquifer recharge results from rare surface water flows. Assessment of surface flow frequency using traditional methods (rain or flow gauges) requires a high-density monitoring network, which is rarely available. This study aimed to determine if satellite optical imagery could detect infrequent surface flows to estimate recharge frequency. Well-used sensors (Landsat and MODiS) have insufficiently high spatio-temporal resolution to detect often short-lived flows in narrow sand rivers characteristic of drylands. Therefore, Sentinel-2 offering 10 m spatial resolution was used for the Shingwidzi River, Limpopo, South Africa. Based on an increase of Normalised Difference Water Index relative to the dry season reference value, detection of surface flows proved feasible with overall accuracy of 91.2% calculated against flow gauge records. The methodology was subsequently tested in the ungauged Molototsi River where flows were monitored by local observers with overall accuracy of 100%. High spatial and temporal resolution allowed for successful detection of surface water, even when flow had receded substantially and when the rivers were partially obstructed by clouds. The presented methodology can supplement monitoring networks where sparse rainfall or flow records exist.
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To secure and increase the availability of clean drinking water in arid and semi-arid regions of the world, construction of sediment filled dams for artificial subsurface storage of water could provide very cost efficient solutions.
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The Loess Mesa Ravine Region and the Loess Hill Ravine Region, cover 200,000 km2 of the Loess Plateau in China and have serious problems of soil and water erosion. Two primary ways to control the sediment pouring into the Yellow River from this area are planting and engineering measures. The former is not suitable for the Loess Plateau due to the arid climate and the barren soil, while some of the latter means, such as terrace farmlands, are vulnerable to floods. As a widespread engineering measure, the check-dam system in gullies is one of the most effective ways to conserve soil and water in the Loess Plateau. At present, the amount of sediment retained by check-dam systems is the largest of all methods and the potential is promising. The dam farmlands so created have become important high-yield croplands or orchards with enriched fertile soil and ample water. This paper reviews the history and principles of check-dams and discusses future theoretical and experimental studies which are needed for the further implementation of this system.
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A successful experiment with a physical model requires necessary conditions of similarity. This study presents an experimental method with a semi-scale physical model. The model is used to monitor and verify soil conservation by check dams in a small watershed on the Loess Plateau of China. During experiments, the model-prototype ratio of geomorphic variables was kept constant under each rainfall event. Consequently, experimental data are available for verification of soil erosion processes in the field and for predicting soil loss in a model watershed with check dams. Thus, it can predict the amount of soil loss in a catchment. This study also mentions four criteria: similarities of watershed geometry, grain size and bare land, Froude number (Fr) for rainfall event, and soil erosion in downscaled models. The efficacy of the proposed method was confirmed using these criteria in two different downscaled model experiments. The B-Model, a large scale model, simulates watershed prototype. The two small scale models, D(a) and D(b), have different erosion rates, but are the same size. These two models simulate hydraulic processes in the B-Model. Experiment results show that while soil loss in the small scale models was converted by multiplying the soil loss scale number, it was very close to that of the B-Model. Obviously, with a semi-scale physical model, experiments are available to verify and predict soil loss in a small watershed area with check dam system on the Loess Plateau, China.
Dam Safety: Stability and Rehabilitation of
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