Back to the drawing board: assessing siting guidelines for sand dams in Kenya

Ngugi, Keziah; Gichaba, Charles Maina; Kathumo, V.M; Ertsen, Maurits W.

doi:10.1007/s40899-020-00417-4

Cited by 20 publications

(53 citation statements)

References 18 publications

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“…Furthermore, the results are significant only for the specific study locations and may or may not be representative of the performance of dams elsewhere. Ngugi et al (2020) recorded from questionnaires, corroborated by field observations and measurements, that 57% of the dams studied did not have water at the end of the short dry period, with a further 7% having no water at the end of the long dry season. These figures are based on a calculated capacity requirement of n households with 5.98 people/household using 20 L/day.…”

Section: Primary Impactssupporting

confidence: 65%

“…The quantity of water supplied to a sand dam also varies spatially, as sand dams constructed in higher order streams will likely receive greater volumes of runoff from upstream catchments. Stream order is weakly correlated to sand dam effectiveness (Ngugi et al, 2020). While spatial and temporal variability of water storage in sand dams is acknowledged in the literature, very little work has examined these variations and developed causation among catchment characteristics and sand dam performance.…”

Section: Water Balancementioning

confidence: 99%

“…While spatial and temporal variability of water storage in sand dams is acknowledged in the literature, very little work has examined these variations and developed causation among catchment characteristics and sand dam performance. The work that has been done is largely inconclusive (Beswetherick et al, 2018;Ngugi et al, 2020), highlighting the importance for more research in this area.…”

Section: Water Balancementioning

confidence: 99%

“…The sedimentation process in sand dams remains a point of confusion and contention in the sand dam community (Nissen-Petersen, 2006;de Trincheria et al, 2018;Eisma and Merwade, 2020;Ngugi et al, 2020). Further surface flow models should be developed to study the sedimentation process of sand dams, and the simulated processes should be studied in parallel with a field study and data monitoring.…”

Section: Surface Flow Modelsmentioning

confidence: 99%

“…In addition to increasing the potential for water storage, sand dams can also help protect stored water from evaporation (Borst and de Haas, 2006;Quinn et al, 2018b;Eisma and Merwade, 2020), increase the quality of stored water (Quinn et al, 2018a;Graber Neufeld et al, 2020), improve overall ecosystem health (Manzi and Kuria, 2012;Ryan and Elsner, 2016;Eisma and Merwade, 2020), and improve the well-being of the local community (de Bruijn and Rhebergen, 2006;Lasage et al, 2008;Pauw et al, 2008;Maddrell, 2010). Despite numerous positive impacts cited in the literature, some studies note that not all sand dams effectively capture and store water (Van Loon and Droogers, 2006;Nissen-Petersen, 2010;de Trincheria et al, , 2018Eisma and Merwade, 2020;Ngugi et al, 2020). For a sand dam to perform optimally, well-sorted sand must be the primary reservoir material.…”

Section: Introductionmentioning

confidence: 99%

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Sand Dams as a Potential Solution to Rural Water Security in Drylands: Existing Research and Future Opportunities

2021

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Sand dams, a rainwater harvesting technique, are small dams constructed across ephemeral streams. During the rainy season, water is stored in the sand that accumulates behind the dam. Sand dams provide communities in drylands with water during the dry season via scoop holes, pools, and shallow wells. Whilst many studies portray sand dams as a positive solution to the growing threat of dryland water insecurity, others highlight their challenges, including poor water quality, evaporation and leakage from some dams, and the contested failure rate and ability of dams to provide water year-round. This article reviews the peer-reviewed and gray literature on sand dams discovered through Scopus and Google Scholar searches, reference lists, and personal contacts. Findings from the collected literature were reviewed and categorized into sand dam hydrology, health and well-being impacts, economic cost and benefits, and water quality topics. In most numerical simulations, sand dams supply water to the local community throughout much of the dry season and exhibit a long-term positive impact on groundwater. Accounts of water storage and loss based on field measurements, conversely, often show that most water is lost due to evapotranspiration and seepage from the sand reservoir rather than community use. Furthermore, the positive impact on local groundwater storage, while variable, is likely seasonal. Sand dams are relatively affordable to build; construction estimates range from 6,000 to 8,500 EUR. However, existing literature suggests that sand dams are likely not a cost-efficient means of supplying water. Nevertheless, successful sand dams can significantly increase water availability and use, whilst reducing traveling time for water collection, subsequently providing a host of secondary benefits from improved hygiene, economic opportunity, and education. Positive impacts, however, are not equally shared and depend on variables, such as abstraction method, catchment, and household location. Furthermore, their water quality is variable, with high microbiological levels detected especially in scoop holes. Whilst sand dams can increase water security and resilience, they may not be an inclusive solution for all. More research is needed to assess the long-term sustainability of sand dams while accounting for the uncertainty of a changing climate.

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Section: Primary Impactssupporting

confidence: 65%

Section: Water Balancementioning

confidence: 99%

Section: Water Balancementioning

confidence: 99%

Section: Surface Flow Modelsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Sand Dams as a Potential Solution to Rural Water Security in Drylands: Existing Research and Future Opportunities

2021

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Large‐scale siting of sand dams: A participatory approach and application in Angolan drylands

et al. 2022

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Sand dams are simple and effective structures built across ephemeral riverbeds in arid/ semiarid regions to harvest water within sand pores and increase water availability and quality for rural communities. The complex morphological, hydrological, social, and economic conditions that make sand dams a beneficial tool for water resilience are largely influenced by the siting phase. Proper location of a sand dam can reduce communities' travel time to water points, reduce water conflicts, and increase food security through expansion of irrigated agriculture. On the other hand, a misplacement of sand dams can, at worst, increase disparities in water access and increase local conflicts. To approach a viable siting of sand dams, most projects are developed and delivered with the community through a bottom-up approach. However, in the case of large-scale projects, remote sensing and biophysical analysis are the dominant approach, leaving the socio-economic component at the margins of the siting strategy and eventually affecting the benefits to local communities. In this paper, we propose a large-scale participatory methodology to sand dams siting, which draws on mixed-methods connecting the conventional top-down biophysical analysis with bottom-up participatory research. We first describe the generic approach developed for sand dams siting in Namibe, a semi-arid region of Southwest of Angola, then we draw on our case to propose a generic approach to large-scale participatory siting beyond Namibe.

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Sand dam contributions to year-round water security monitored through telemetered handpump data

Ritchie,

Holman,

Parker

et al. 2023

Environ Monit Assess

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Sand dams are a form of rainwater harvesting, prolific in arid and semi-arid lands. Water is provided partly via handpumps, which, as the only improved method of abstraction from sand dams, are important for drinking water security. Accelerometers and cellular transmitters were fitted to 30 handpumps by the Africa Sand Dam Foundation (ASDF) in 2019 to monitor the use and reliability of the handpumps by recording hourly water volume abstracted. Data from April 2019 to October 2021 for 26 of these sites, alongside qualitative data, were analysed and each handpump’s contribution to year-round water security was explored, focusing on the long dry season when water supply from other sources is compromised. Abstraction was over 20 times higher in the long dry season than in any other season, and at sites with higher salinity, higher livestock use, and larger dam wall area. At 21 wells, abstraction was still being recorded at the end of at least one long dry season; however, high spatial and temporal heterogeneity between pumps and seasons means that not all sand dams deliver reliable water supply year-round. Quantifying the contribution that sand dams make to water security is crucial for understanding their resilience against a changing climate and can aid decision makers when choosing the most appropriate water management technique. Knowledge of temporal and site heterogeneity in abstraction can inform when other water sources need increasing and can help with sand dam design optimisation. Overall, our results indicate the positive contribution that sand dams make to year-round water security through the water that is abstracted through handpumps.

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Back to the drawing board: assessing siting guidelines for sand dams in Kenya

Cited by 20 publications

References 18 publications

Sand Dams as a Potential Solution to Rural Water Security in Drylands: Existing Research and Future Opportunities

Sand Dams as a Potential Solution to Rural Water Security in Drylands: Existing Research and Future Opportunities

Large‐scale siting of sand dams: A participatory approach and application in Angolan drylands

Sand dam contributions to year-round water security monitored through telemetered handpump data

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