Your search found 12 records
1 Taylor, R. G.; Howard, K. W. F. 1996. Averting shallow-well contamination in Uganda. In Pickford, J.; Barker, P.; Elson, B.; Ferguson, C.; Parr, J.; Saywell, D.; Shaw, R.; Skinner, B. (Eds.), Sustainability of water and sanitation systems: Selected papers of the 21st WEDC International Conference Kampala, Uganda, 1995. London, UK; Leicestershire, UK: IT Publications; WEDC. pp.80-83.
(Location: IWMI-HQ Call no: 628.1 G000 PIC Record No: H027107)
2 Taylor, R. G.; Howard, K. W. F. 1996. Groundwater recharge in the Victoria Nile Basin of East Africa: Support for the soil Moisture balance approach using stable isotope tracers and flow modelling. Journal of Hydrology, 180:31-53.
Groundwater ; Flow ; Models ; Recharge ; Soil moisture ; Aquifers ; Precipitation / Africa / Uganda / Victoria Nile Basin
(Location: IWMI-HQ Call no: P 6883 Record No: H034834)
3 MacDonald, A. M.; Taylor, R. G.; Bonsor, H. C. 2012. Groundwater in Africa: is there sufficient water to support the intensification of agriculture from 'land grabs'? In Allan, T.; Keulertz, M.; Sojamo, S.; Warner, J. (Eds.). Handbook of land and water grabs in Africa: foreign direct investment and food and water security. London, UK: Routledge. pp.376-383.
Land acquisitions ; Groundwater development ; Water storage ; Groundwater irrigation ; Water availability ; Crop production ; Intensification / Africa
(Location: IWMI HQ Call no: 333.91 G000 ALL Record No: H045689)
4 Gurdak, J. J.; Leblanc, M.; Aureli, A.; Resende, T. C.; Faedo, G.; Green, T. R.; Tweed, S.; Longuevergne, L.; Allen, D. M.; Elliott, J. F.; Taylor, R. G.; Conti, K. 2015. GRAPHIC position paper and call to action. Groundwater and climate change: mitigating the global groundwater crisis and adapting to climate change. Paris, France: UNESCO International Hydrological Programme (IHP). GRAPHIC - Groundwater Resources Assessment under the Pressures of Humanity and Climate Change Project. 16p.
Groundwater management ; Groundwater recharge ; Climate change adaptation ; Water resources ; Water scarcity ; Assessment ; Water quality ; Water policy ; Aquifers ; Monitoring ; International cooperation ; Strategies ; Agricultural policy ; Food production ; Gender ; Women ; Sustainability
(Location: IWMI HQ Call no: e-copy only Record No: H047352)
http://www.graphicnetwork.net/wp-content/uploads/2015/11/GRAPHIC_pp20151.pdf
https://vlibrary.iwmi.org/pdf/H047352.pdf
https://vlibrary.iwmi.org/pdf/H047352.pdf
(1.55 MB) (1.55 MB)
5 Kolusu, S. R.; Shamsudduha, M.; Todd, M. C.; Taylor, R. G.; Seddon, D.; Kashaigili, J. J.; Ebrahim, Girma Y.; Cuthbert, M. O.; Sorensen, J. P. R.; Villholth, Karen G.; MacDonald, A. M.; MacLeod, D. A. 2019. The El Nino event of 2015-2016: climate anomalies and their impact on groundwater resources in East and Southern Africa. Hydrology and Earth System Sciences, 23: 1751-1762. [doi: https://doi.org/10.5194/hess-23-1751-2019]
El Nino ; Groundwater management ; Water resources ; Water storage ; Climate change ; Rainfall ; Drought ; Water balance ; Water levels ; Surface water ; Precipitation ; Evapotranspiration ; Satellite imagery ; Satellite observation / East Africa / SouthernAfrica / Limpopo Basin
(Location: IWMI HQ Call no: e-copy only Record No: H049164)
https://www.hydrol-earth-syst-sci.net/23/1751/2019/hess-23-1751-2019.pdf
https://vlibrary.iwmi.org/pdf/H049164.pdf
https://vlibrary.iwmi.org/pdf/H049164.pdf
(2.80 MB)
The impact of climate variability on groundwater storage has received limited attention despite widespread dependence on groundwater as a resource for drinking water, agriculture and industry. Here, we assess the climate anomalies that occurred over Southern Africa (SA) and East Africa, south of the Equator (EASE), during the major El Niño event of 2015–2016, and their associated impacts on groundwater storage, across scales, through analysis of in situ groundwater piezometry and Gravity Recovery and Climate Experiment (GRACE) satellite data. At the continental scale, the El Niño of 2015–2016 was associated with a pronounced dipole of opposing rainfall anomalies over EASE and Southern Africa, north–south of ~12° S, a characteristic pattern of the El Niño–Southern Oscillation (ENSO). Over Southern Africa the most intense drought event in the historical record occurred, based on an analysis of the cross-scale areal intensity of surface water balance anomalies (as represented by the standardised precipitation evapotranspiration index – SPEI), with an estimated return period of at least 200 years and a best estimate of 260 years. Climate risks are changing, and we estimate that anthropogenic warming only (ignoring changes to other climate variables, e.g. precipitation) has approximately doubled the risk of such an extreme SPEI drought event. These surface water balance deficits suppressed groundwater recharge, leading to a substantial groundwater storage decline indicated by both GRACE satellite and piezometric data in the Limpopo basin. Conversely, over EASE during the 2015–2016 El Niño event, anomalously wet conditions were observed with an estimated return period of ~10 years, likely moderated by the absence of a strongly positive Indian Ocean zonal mode phase. The strong but not extreme rainy season increased groundwater storage, as shown by satellite GRACE data and rising groundwater levels observed at a site in central Tanzania. We note substantial uncertainties in separating groundwater from total water storage in GRACE data and show that consistency between GRACE and piezometric estimates of groundwater storage is apparent when spatial averaging scales are comparable. These results have implications for sustainable and climate-resilient groundwater resource management, including the potential for adaptive strategies, such as managed aquifer recharge during episodic recharge events.
6 Cuthbert, M. O.; Taylor, R. G.; Favreau, G.; Todd, M. C.; Shamsudduha, M.; Villholth, Karen G.; MacDonald, A. M.; Scanlon, B. R.; Kotchoni, D. O. V.; Vouillamoz, J.-M.; Lawson, F. M. A.; Adjomayi, P. A.; Kashaigili, J.; Seddon, D.; Sorensen, J. P. R.; Ebrahim, Girma Yimer; Owor, M.; Nyenje, P. M.; Nazoumou, Y.; Goni, I.; Ousmane, B. I.; Sibanda, T.; Ascott, M. J.; Macdonald, D. M. J.; Agyekum, W.; Koussoube, Y.; Wanke, H.; Kim, H.; Wada, Y.; Lo, M.-H.; Oki, T.; Kukuric, N. 2019. Observed controls on resilience of groundwater to climate variability in sub-Saharan Africa. Nature, 572(7768):230-234. [doi: https://doi.org/10.1038/s41586-019-1441-7]
Groundwater recharge ; Climate change ; Resilience ; Groundwater table ; Observation ; Precipitation ; Hydrology ; Hydrography ; Models ; Arid zones ; Rain / Africa South of Sahara / Benin / Uganda / United Republic of Tanzania / Zimbabwe / South Africa / Namibia / Niger / Ghana / Burkina Faso
(Location: IWMI HQ Call no: e-copy only Record No: H049316)
https://www.nature.com/articles/s41586-019-1441-7.epdf?author_access_token=UgizrPwmrGzlbL33bjbvQdRgN0jAjWel9jnR3ZoTv0M3C122Ih9FQbr0PbeOlDAX9EZlbSwXsaUcJ-Vq-8EelgPfWJQTdVE-2_3g7yypNR4C-qTOMe7Ux1weufjBdaT9SyaKgJjfKYgJ2fqsjIRLng%3D%3D
https://vlibrary.iwmi.org/pdf/H049316.pdf
https://vlibrary.iwmi.org/pdf/H049316.pdf
(7.21 MB)
Groundwater in sub-Saharan Africa supports livelihoods and poverty alleviation1,2 , maintains vital ecosystems, and strongly influences terrestrial water and energy budgets3 . Yet the hydrological processes that govern groundwater recharge and sustainability—and their sensitivity to climatic variability—are poorly constrained4,5 . Given the absence of firm observational constraints, it remains to be seen whether model-based projections of decreased water resources in dry parts of the region4 are justified. Here we show, through analysis of multidecadal groundwater hydrographs across sub-Saharan Africa, that levels of aridity dictate the predominant recharge processes, whereas local hydrogeology influences the type and sensitivity of precipitation–recharge relationships. Recharge in some humid locations varies by as little as five per cent (by coefficient of variation) across a wide range of annual precipitation values. Other regions, by contrast, show roughly linear precipitation–recharge relationships, with precipitation thresholds (of roughly ten millimetres or less per day) governing the initiation of recharge. These thresholds tend to rise as aridity increases, and recharge in drylands is more episodic and increasingly dominated by focused recharge through losses from ephemeral overland flows. Extreme annual recharge is commonly associated with intense rainfall and flooding events, themselves often driven by large-scale climate controls. Intense precipitation, even during years of lower overall precipitation, produces some of the largest years of recharge in some dry subtropical locations. Our results therefore challenge the ‘high certainty’ consensus regarding decreasing water resources4 in such regions of sub-Saharan Africa. The potential resilience of groundwater to climate variability in many areas that is revealed by these precipitation–recharge relationships is essential for informing reliable predictions of climate-change impacts and adaptation strategies.
7 Faye, S. C.; Diongue, M. L.; Pouye, A.; Gaye, C. B.; Travi, Y.; Wohnlich, S.; Faye, S.; Taylor, R. G.. 2019. Tracing natural groundwater recharge to the Thiaroye Aquifer of Dakar, Senegal. Hydrogeology Journal, 27(3):1067-1080. (Special issue: Groundwater in Sub-Saharan Africa) [doi: https://doi.org/10.1007/s10040-018-01923-8]
Groundwater recharge ; Aquifers ; Semiarid zones ; Urban areas ; Groundwater flow ; Groundwater table ; Monsoon climate ; Rain ; Chemical composition ; Isotopes / Senegal / Dakar / Thiaroye aquifer
(Location: IWMI HQ Call no: e-copy only Record No: H049362)
https://link.springer.com/content/pdf/10.1007%2Fs10040-018-01923-8.pdf
https://vlibrary.iwmi.org/pdf/H049362.pdf
https://vlibrary.iwmi.org/pdf/H049362.pdf
(5.43 MB) (5.43 MB)
Urban groundwater in Sub-Saharan Africa provides vital freshwater to rapidly growing cities. In the Thiaroye aquifer of Dakar (Senegal), groundwater within Quaternary unconsolidated sands provided nearly half of the city’s water supply into the 1980s. Rising nitrate concentrations traced to faecal contamination sharply curtailed groundwater withdrawals, which now contribute just 5% to Dakar’s water supply. To understand the attenuation capacity of this urban aquifer under a monsoonal semi-arid climate, stable-isotope ratios of O and H and radioactive tritium (3H), compiled over several studies, are used together with piezometric data to trace the origin of groundwater recharge and groundwater flowpaths. Shallow groundwaters derive predominantly from modern rainfall (tritium >2 TU in 85% of sampled wells). d18O and d2H values in groundwater vary by >4 and 20‰, respectively, reflecting substantial variability in evaporative enrichment prior to recharge. These signatures in groundwater regress to a value on the local meteoric water line that is depleted in heavy isotopes relative to the weighted-mean average composition of local rainfall, a bias that suggests recharge derives preferentially from isotopically depleted rainfall observed during the latter part of the monsoon (September). The distribution of tritium in groundwater is consistent with groundwater flowpaths to seasonal lakes and wetlands, defined by piezometric records. Piezometric data further confirm the diffuse nature and seasonality of rain-fed recharge. The conceptual understanding of groundwater recharge and flow provides a context to evaluate attenuation of anthropogenic recharge that is effectively diffuse and constant from the vast network of sanitation facilities that drain to this aquifer.
8 Chan, W. C. H.; Thompson, J. R.; Taylor, R. G.; Nay, A. E.; Ayenew, T.; MacDonald, A. M.; Todd, M. C. 2020. Uncertainty assessment in river flow projections for Ethiopia’s Upper Awash Basin using multiple GCMs [General Circulation Models] and hydrological models. Hydrological Sciences Journal, 65(10):1720-1737. [doi: https://doi.org/10.1080/02626667.2020.1767782]
River basins ; Flow discharge ; Forecasting ; Hydrology ; Models ; Calibration ; Climate change ; Precipitation ; Evapotranspiration ; Assessment ; Uncertainty / Ethiopia / Upper Awash Basin
(Location: IWMI HQ Call no: e-copy only Record No: H049953)
(4.45 MB)
Uncertainty in climate change impacts on river discharge in the Upper Awash Basin, Ethiopia, is assessed using five MIKE SHE hydrological models, six CMIP5 general circulation models (GCMs) and two representative concentration pathways (RCP) scenarios for the period 2071–2100. Hydrological models vary in their spatial distribution and process representations of unsaturated and saturated zones. Very good performance is achieved for 1975–1999 (NSE: 0.65–0.8; r: 0.79–0.93). GCM-related uncertainty dominates variability in projections of high and mean discharges (mean: –34% to +55% for RCP4.5, – 2% to +195% for RCP8.5). Although GCMs dominate uncertainty in projected low flows, inter-hydrological model uncertainty is considerable (RCP4.5: –60% to +228%, RCP8.5: –86% to +337%). Analysis of variance uncertainty attribution reveals that GCM-related uncertainty occupies, on average, 68% of total uncertainty for median and high flows and hydrological models no more than 1%. For low flows, hydrological model uncertainty occupies, on average, 18% of total uncertainty; GCM-related uncertainty remains substantial (average: 28%).
9 Kebede, S.; Charles, K.; Godfrey, S.; MacDonald, A.; Taylor, R. G.. 2021. Regional-scale interactions between groundwater and surface water under changing aridity: evidence from the River Awash Basin, Ethiopia. Hydrological Sciences Journal, 15p. (Online first) [doi: https://doi.org/10.1080/02626667.2021.1874613]
Groundwater flow ; Surface water ; Drylands ; River basins ; Water security ; Lakes ; Reservoirs ; Water resources ; Aquifers ; Stream flow ; Discharges ; Salinity ; Irrigation water ; Water budget ; Wetlands ; Hydrology ; Electrical conductivity ; Isotopes / Ethiopia / Awash River Basin / Lake Beseka
(Location: IWMI HQ Call no: e-copy only Record No: H050234)
https://www.tandfonline.com/doi/pdf/10.1080/02626667.2021.1874613
https://vlibrary.iwmi.org/pdf/H050234.pdf
https://vlibrary.iwmi.org/pdf/H050234.pdf
(8.05 MB) (8.05 MB)
Relationships between surface waters and groundwaters at basin scale are rarely investigated but have important implications for water resource development and management. Here, we integrate evidence from geochemical tracers and piezometry to advance the understanding of regional-scale, groundwater–surface water interactions in the River Awash Basin of Ethiopia. Hydrological characteristics are consistent with those observed in other semi-arid and arid basins where rivers are predominantly losing and act as a source of recharge rather than as a sink for groundwater discharge. Further, regional groundwater flow originating from the highlands exits the catchment rather than discharging to the riverine drainage. Consequently, groundwater abstraction from several regional-scale aquifers in the lowlands is not expected to impact river flow. However, salinity presents a major threat to irrigation and water supply. We identify critical areas for managing inflows, water use, wetlands and water quality that have significant implications for water security across the basin.
10 Sorensen, J. P. R.; Davies, J.; Ebrahim, Girma Y.; Lindle, J.; Marchant, B. P.; Ascott, M. J.; Bloomfield, J. P.; Cuthbert, M. O.; Holland, M.; Jensen, K. H.; Shamsudduha, M.; Villholth, Karen G.; MacDonald, A. M.; Taylor, R. G.. 2021. The influence of groundwater abstraction on interpreting climate controls and extreme recharge events from well hydrographs in semi-arid South Africa. Hydrogeology Journal, 29(8):2773-2787. [doi: https://doi.org/10.1007/s10040-021-02391-3]
Groundwater extraction ; Groundwater recharge ; Well hydrographs ; Semiarid climate ; Catchment areas ; Groundwater table ; Rain ; River flow ; Stream flow ; Extreme weather events ; El Nino-Southern Oscillation ; Hydrogeology ; Boreholes ; Spatial distribution ; Land use / South Africa / Limpopo / Mogalakwena Catchment / Sand River Catchment
(Location: IWMI HQ Call no: e-copy only Record No: H050671)
https://link.springer.com/content/pdf/10.1007/s10040-021-02391-3.pdf
https://vlibrary.iwmi.org/pdf/H050671.pdf
https://vlibrary.iwmi.org/pdf/H050671.pdf
(6.26 MB) (6.26 MB)
There is a scarcity of long-term groundwater hydrographs from sub-Saharan Africa to investigate groundwater sustainability, processes and controls. This paper presents an analysis of 21 hydrographs from semi-arid South Africa. Hydrographs from 1980 to 2000 were converted to standardised groundwater level indices and rationalised into four types (C1–C4) using hierarchical cluster analysis. Mean hydrographs for each type were cross-correlated with standardised precipitation and streamflow indices. Relationships with the El Nino– Southern Oscillation (ENSO) were also investigated. The four hydrograph types show a transition of autocorrelation over increasing timescales and increasingly subdued responses to rainfall. Type C1 strongly relates to rainfall, responding in most years, whereas C4 notably responds to only a single extreme event in 2000 and has limited relationship with rainfall. Types C2, C3 and C4 have stronger statistical relationships with standardised streamflow than standardised rainfall. C3 and C4 changes are significantly (p < 0.05) correlated to the mean wet season ENSO anomaly, indicating a tendency for substantial or minimal recharge to occur during extreme negative and positive ENSO years, respectively. The range of different hydrograph types, sometimes within only a few kilometres of each other, appears to be a result of abstraction interference and cannot be confidently attributed to variations in climate or hydrogeological setting. It is possible that high groundwater abstraction near C3/C4 sites masks frequent small-scale recharge events observed at C1/C2 sites, resulting in extreme events associated with negative ENSO years being more visible in the time series.
11 Nayebare, J. G.; Owor, M. M.; Kulabako, R.; Taylor, R. G.. 2021. Faecal contamination pathways of shallow groundwater in low-income urban areas: implications for water resource planning and management. Water Practice and Technology, 12p. (Online first) [doi: https://doi.org/10.2166/wpt.2021.110]
Faecal pollution ; Groundwater ; Shallow wells ; Sanitation ; Chemical contamination ; Water quality ; Water resources ; Planning ; Water management ; Urban areas ; Hydrogeology ; Wet season ; Dry season ; Nitrates ; Models / Uganda / Kalungu / Lukaya
(Location: IWMI HQ Call no: e-copy only Record No: H050760)
https://iwaponline.com/wpt/article-pdf/doi/10.2166/wpt.2021.110/967090/wpt2021110.pdf
https://vlibrary.iwmi.org/pdf/H050760.pdf
https://vlibrary.iwmi.org/pdf/H050760.pdf
(0.43 MB) (436 KB)
Shallow groundwater is vulnerable to faecal contamination, especially in low-income urban areas where use of on-site sanitation facilities is high. This paper explores statistical relationships between potential factors influencing contaminant pathways (i.e., variables) and observed faecal contamination of shallow groundwater, represented by nitrate concentrations and counts of Escherichia coli (i.e., response function) in a small, growing town in Uganda over dry and wet seasons in 2018 and 2019. A statistically significant (p = 0.004) multiple linear regression model from dry-season E. coli counts in 2018 identifies medium sanitary risk levels and modes of construction as significant pathways (p = 0.01). Water source depth (<20 m) and proximity (>10 m) to a pit latrine were also significant (p<0.05) in both hydrogeological formations. No significant linear regression models were established for NO3 during both seasons due to low pH and rapid infiltration velocities; inconsistent sample timing during the wet season impaired the significance of the statistical models of E. coli counts. We show that modes of construction of water sources and pit latrines play key roles in determining the quality of the shallow groundwater in urban environments. Greater emphasis is therefore required to improve the functionality and sustainability of on-site water sources and pit latrines.
12 Bellwood-Howard, I.; Thompson, J.; Shamsudduha, M.; Taylor, R. G.; Mosha, D. B.; Gebrezgi, Gebrehaweria; Tarimo, A. K. P. R.; Kashaigili, J. J.; Nazoumou, Y.; Tiekoura, O. 2022. A multicriteria analysis of groundwater development pathways in three river basins in Sub-Saharan Africa. Environmental Science and Policy, 138:26-43. [doi: https://doi.org/10.1016/j.envsci.2022.09.010]
Groundwater management ; River basins ; Water policies ; Water governance ; Water availability ; Large-scale farming ; Small-scale farming ; Water use ; Water users ; Multiple use ; Water quality ; Environmental sustainability ; Groundwater extraction ; Stakeholders ; Communities ; Modelling ; Uncertainty / Africa South of Sahara / Ethiopia / Niger / United Republic of Tanzania / Great Ruaha Sub-Catchment / Iullemmeden Basin / Awash Basin
(Location: IWMI HQ Call no: e-copy only Record No: H051559)
https://www.sciencedirect.com/science/article/pii/S146290112200288X/pdfft?md5=4e23255036c0e457072d97d30d062c6e&pid=1-s2.0-S146290112200288X-main.pdf
https://vlibrary.iwmi.org/pdf/H051559.pdf
https://vlibrary.iwmi.org/pdf/H051559.pdf
(10.10 MB) (10.1 MB)
Reliance on groundwater in Sub-Saharan Africa is growing and expected to rise as surface water resource variability increases under climate change. Major questions remain about how groundwater will be used, and who informs these decisions. We represent different visions of groundwater use by ‘pathways’: politically and environmentally embedded socio-technological regimes for governing and managing groundwater systems. We presented policy actors (9 sets), development and research stakeholders (4 sets), and water users (6 sets) in three river basins in Ethiopia, Niger and Tanzania with information on the social and environmental impacts of six ‘Groundwater Development Pathways’, before gathering their opinions on each, through Multicriteria Mapping (MCM). Participants preferred pathways of low-intensity use, incorporating multiple agricultural, pastoral and domestic purposes, to high-intensity single-use pathways. Water availability and environmental sustainability, including water quality, were central concerns. Participants recognised that all groundwater uses potentially impinge upon one another affecting both the quantity and quality of abstracted water. Across participant groups there was ambiguity about what the most important water use was; each expressed demands for more detailed, certain modelling data. Water users preferred community or municipal-scale management regimes, perceiving that water quality was more likely to be safeguarded by institutions at these levels, whereas policy and development actors preferred individual-scale management, viewed as more efficient in terms of operation and maintenance. We conclude that MCM, combined with more detailed modelling, can provide an effective framework for policy actors to understand other stakeholders’ perspectives on groundwater development futures, enabling equitable, inclusive decision-making and governance.
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