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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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... 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. ...
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. ...
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.
... It's important to note that the design and construction of sand dams often deviate from the guidelines outlined in technical and engineering manuals, as experience has shown that practical knowledge and adaptation play significant roles in their successful implementation. [1] A groundwater dam is a structure that obstructs the natural flow of groundwater and stores water below the ground surface. There are basically two types of groundwater dams: i) sub-surface dams and ii) sand-storage dams. ...
In dry land areas like Somaliland shortage of water is very common. People have to travel for long distances to find water, and after it rains, most of the water is lost to evaporation or surface run off. The challenge in arid and semi-arid climates is how to harvest rainwater; most of villages in Somaliland need how to harvest rainwater and running water through their dry valleys. This study aimed to evaluate the positive and negative impact of existing water infrastructure (sand dams) in dry rivers in Cadadley district and to compare these with appraisal of sites yet to be developed that can be constructed sand dams in Cadadley region Somaliland. This study employs a method known as probing, which involves hammering a rod into the middle of the riverbed until it makes contact with the floor beneath the sand, producing a dull sound. The level of the sand is then marked on the rod, which is subsequently pulled straight up without any twisting. The crucial factor in determining the location for constructing a sand storage dam is the depth of the basement or impermeable layer relative to the riverbed surface. Ideally, the dam should be built where the impermeable layer is closest to the riverbed surface. The result shows that sand dam need reconstruction because of short of their spill ways and there is poor choice location.
... After construction, the sand dam is allowed to mature: a sand bed initially forms upstream and is transported into the dam basin during a heavy storm, which repeats until eventually, the basin fills with coarse sediment that can extend 500 m or more upstream (Fig. 1). Consistent with approaches outlined in Maddrell (2018), the wingwalls are constructed to full design height and the spillway in stages as the volume of harvested sediment reaches the dam wall following storm events. Because fine sediment in a sand dam can obstruct water abstraction, this staged design ensures that only coarse sediment is captured behind the dam wall and cyclonic rains during the wet season are able to pass, transporting fine sediment through the dam basin. ...
Climate change is increasing the frequency and severity of droughts in semi-arid regions. Small-scale water storage can help build drought resilience, particularly in rural areas with no access to formal water infrastructure. Sand dams, which store water by capturing water in sand-filled ephemeral rivers during the wet season, are one promising storage option. While emerging studies indicate tentative evidence of their benefits, the focus on resilience is under-addressed. This study evaluates the impact of sand dams on resilience to climate variability and changes through a participatory case study approach in the Shashe catchment, a semi-arid catchment shared by Botswana and Zimbabwe. Participatory research was conducted via site inspections, focus group discussions, and interviews at 20 sand dams utilized by 19 villages across the Zimbabwean portion of the Shashe catchment. The results show that sand dams significantly improved local water availability, most notably with a significant increase in the number of months per year that water could be collected from the dam site (mean = 6.5 months before, to mean = 10.9 months after construction, p < 0.05). This increase is also reflected in drought years (mean = 5.8 months before, to mean = 9.6 months after construction, p < 0.05). Sand dams also contribute to the adaptive capacity of communities via key benefits such as diversification of livelihood activities, improved health and hygiene, and reduced erosion in the surrounding area due to increased vegetation. In sum, the study demonstrates clear benefits to communities facing drought, supporting calls to elevate sand dams on the development agenda.
... Due to the high rate of evapotranspiration found in the ASALs, open water sources such as dams and water pans are not reliable, making sand dams more suitable structures for water storage. Water can be obtained from the sand dams either through scooping holes or shallow wells [14]. Being key water resources during the dry seasons for the people and livestock in the ASALs of Kenya, it is critical to frequently monitor their water quality to guarantee access to quality water as envisioned in SDGs as well as informing water quality mitigation measures [15]. ...
... Due to the high rate of evapotranspiration found in the ASALs, open water sources such as dams and water pans are not reliable, making sand dams more suitable structures for water storage. Water can be obtained from the sand dams either through scooping holes or shallow wells [14]. Being key water resources during the dry seasons for the people and livestock in the ASALs of Kenya, it is critical to frequently monitor their water quality to guarantee access to quality water as envisioned in SDGs as well as informing water quality mitigation measures [15]. ...
Communities in semi-arid lands use sand dams to enhance access water during the dry seasons. However, there is limited information on the quality of water derived from these sand dams, especially in degraded lands where storm surface runoff poses contamination risk. Thus, this study aimed at assessing the spatial–temporal variations in water quality of sand dams in Chepareria, West Pokot County in Kenya. Water samples were collected from scooping holes across 18 purposefully selected sand dams. Results obtained showed significant differences in water quality based on a sand dam’s age and location of the scooping holes, but the magnitude of these differences differed with specific properties. For instance, in recently constructed sand dams (<1 year), scooping holes near the sand dam wall had lower pH values (8.5) than holes scooped a distance from the sand dam wall (9.2). For total dissolved solutes and microbial properties, sand dam age had the greatest impact, over the location of the scooping holes. For example, water obtained from <1 year old sand dams had significantly higher TDS with an average value of 100.3 mg L−1. The thermotolerant coliforms (TTC) exceeded the maximum allowable levels recommended by The World Health Organization. Thus, water obtained from these sand dams should be treated before consumption. Finally, sand dams meant for domestic water harvesting should be protected. Shallow wells with appropriate aprons for effective protection against contamination should be installed to enhance abstraction of safe water from sand dams.
... Traditionally, sand dams have been used to harvest and conserve water for domestic and agricultural purposes in the arid and semi-arid lands of Kenya (Maddrell, 2018;Neufeld et al., 2021). Through improving water availability in the sand aquifers and their surroundings, sand dams have proven a suitable tool for enhancing adaptations of ASALs to climate change through vegetation regeneration (Lasage et al., 2008) and conserving and increasing availability of domestic water during the dry seasons for durations up to four months (Ryan & Elsner, 2016). ...
Arid and semi-arid lands occupy currently 88% of arable land mass in Kenya, a region with significant diversity of production systems and economic opportunities. However, these areas are characterised by low and erratic rainfall, hence challenges to agriculture and socioeconomic development in the wake of an increasing population and the impacts of climate change. This review seeks to identify key challenges and opportunities associated with the management of agricultural soils in these arid and semi-arid communities. Arid and semi-arid regions in Kenya are dominated by 10 soil types; Solanchaks, Solonetz, Cambisols, Arenosols, Leptosols, Vertisols, Fluvisols, Phoezems, Calcisols, and Gypsisols. Among the main soil fertility challenges in these soils are moisture stress, high erodibility, and low organic matter content, salinity, and sodium toxicity, the deficiencies of mainly N, P, Zn, and Fe, hence the vulnerability of over 14 million inhabitants to the shocks of low crop and pasture production. Moreover, the adoption of soil conservation practices remains low as existing soil fertility management technologies have been criticized for being too abstract and not providing context and site-specific solutions. Improving soil fertility and moisture levels enhances soil ecosystem functions and food and pasture production in these regions. Encouraging farmers to join soil and water conservation groups, while providing economic incentives, could potentially accelerate the adoption of soil and water practices at the farm level through pulling resources together. Future research to validate a site and context-specific integrated soil fertility improvement technologies for these soils is evitable to enhance soil functions, agricultural production and livelihood at house hold level.
... Due to the high rate of evapotranspiration found in the ASALs, open water sources such as dams and water pans are not reliable, making sand dams more suitable structures for water storage. Water can be obtained from the sand dams either through scooping holes or shallow wells [14]. Being key water resources during the dry seasons for the people and livestock in the ASALs of Kenya, it is critical to frequently monitor their water quality to guarantee access to quality water as envisioned in SDGs as well as informing water quality mitigation measures [15]. ...
Conventional approach of establishing soil conservation strategies in degraded drylands has had negligible success. This has been contributed by many constraints, including; lagging of farmers in technology adoption, inadequate resources, and lack of motivation. Thus, a study was conducted among three agro-pastoral community farmer groups in Korellach Parak, Kapkitony, and Kaporowo villages domiciled in Chepareria ward, West Pokot, Kenya, to assess contributory factors and consequences of adopting terracing as a soil conservation measure. Mixed methods comprising; one-on-one interviews, cross-sectional field measurements, and focus group discussions (FGDs), were used for data collection. Results indicate that the agro-pastoral communities are fully aware of soil degradation and its impacts. Besides terracing, farmers practice stone bands, enclosures, agroforestry, and ridges. Terracing is a recently adopted farm-level soil conservation practice achieved through organized farmer groups dubbed “Kemorokorenyo” (meaning let us reclaim our land) merry-go-round. Within the three villages, 60% of the households have their farms terraced with an average terrace volume of 103.8±21.45m3, 105.89±33.126m3, and 129.6±15.966m3 in Parak Kapkitony and Kaporowo, respectively. Rapid sedimentation of terraces dykes, which contributes to the reduced effectiveness of the terrace system was identified as the major challenge. The sediment volume significantly differs along the slope, with the highest sediment build-up experienced on high slopes as shown by the Kruskal Wallis test; H (2) =6.699, p=0.035. Terrace embankments reinforcement practice to counter sedimentation challenge has faced slow adoption. The poor reinforcement is attributable to the lack of knowledge on suitable local context multipurpose materials to meet the community’s needs.
... 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). ...
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.
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.
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.
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.
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