Groundwater recharge, flow and hydrogeochemical evolution in a complex volcanic aquifer system, central Ethiopia

Demlie, Molla; Wohnlich, Stefan; Wisotzky, Frank; Gizaw, Birhanu

doi:10.1007/s10040-007-0163-3

Cited by 88 publications

(55 citation statements)

References 18 publications

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“…Major ions of groundwater in the study area are thus derived from the weathering of minerals in host rocks. Along the Cameroon Volcanic Line [7,39,40] and elsewhere in other countries [41,42], analogous observations have been reported in springs. Those observations are confirmed by the Gibbs diagram [43] for the study area (Figure 4a,b) which indicates that water-rock interaction is the dominant process controlling the main chemical composition of groundwater.…”

Section: Discussionsupporting

confidence: 80%

Importance of Rocks and Their Weathering Products on Groundwater Quality in Central-East Cameroon

et al. 2017

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Abstract:The present work highlights the influence of lithology on water quality in Méiganga and its surroundings. The main geological formations in this region include gneiss, granite and amphibolite. The soils developed on these rocks are of ABC type, which are acidic to slightly acidic. Electrical conductivity (EC), organic matter, total nitrogen, nitrate-nitrogen, sulfate, chloride, phosphorus and exchangeable base values were low to very low in the soil samples. Groundwater samples were investigated for their physicochemical characteristics. The wide ranges of EC values (15.1-436 µS/cm) and total dissolved solids (9-249 mg/L) revealed the heterogeneous distribution of hydrochemical processes within the groundwater of the area. The relative abundance of major dissolved species (mg/L) was Ca 2+ > Na + > Mg 2+ > K + for cations and HCO 3 − >> NO 3 − > Cl − > SO 4 2− for anions.All the groundwater samples were soft, with total hardness values (2.54-136.65 mg/L) below the maximum permissible limits of the World Health Organization (WHO) guideline. The majority of water samples (67%) were classified as mixed CaMg-HCO 3 type. Alkaline earth metal contents dominated those of alkali metals in 66.66% of samples. Thus, for the studied groundwater, Mg 2+ and Ca 2+ ion adsorption by clay minerals was almost nonexistent; this implies their release into the solution, which accounts for their high concentrations compared to alkali metals. Ion geochemistry revealed that water-rock interactions (silicate weathering) and ion exchange processes regulated the groundwater chemistry. One water sample points towards the evaporation domain of this diagram, indicating that groundwater probably does not originate from a deeper system. Kaolinite is the most stable secondary phase in the waters in the study area, in accordance with the geochemical process of monosiallitization, which predominated in the humid tropical zone.

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Section: Discussionsupporting

confidence: 80%

Importance of Rocks and Their Weathering Products on Groundwater Quality in Central-East Cameroon

et al. 2017

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“…Despite their limited extent, they are highly significant aquifers since they underlie many of the poorest and most drought vulnerable areas. The groundwater potential of volcanic rocks varies considerably, reflecting the complexity of the geology (Demlie et al, 2007).…”

Section: Groundwater Resources In Africamentioning

confidence: 99%

What impact will climate change have on rural groundwater supplies in Africa?

MacDonald

Calow

Macdonald

et al. 2009

Hydrological Sciences Journal

123

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One of the key uncertainties surrounding the impacts of climate change in Africa is the effect on the sustainability of rural water supplies. Many of these water supplies abstract from shallow groundwater (<50 m) and are the sole source of safe drinking water for rural populations. Analysis of existing rainfall and recharge studies suggests that climate change is unlikely to lead to widespread catastrophic failure of improved rural groundwater supplies. These require only 10 mm of recharge annually per year to support a hand pump, which should still be achievable for much of the continent, although up to 90 million people may be affected in marginal groundwater recharge areas (200-500 mm annual rainfall). Lessons learnt from groundwater source behaviour during recent droughts, substantiated by groundwater modelling, indicate that increased demand on dispersed water points, as shallow unimproved sources progressively fail, poses a much greater risk of individual source failure than regional resource depletion. Low yielding sources in poor aquifers are most at risk. Predicted increased rainfall intensity may also increase the risk of contamination of very shallow groundwater. Looking to the future, an increase in major groundwater-based irrigation systems, as food prices rise and surface water becomes more unreliable, may threaten long-term sustainability as competition for groundwater increases. To help prepare for increased climate variability, it is essential to understand the balance between water availability, access to water, and use/demand. In practice, this means increasing access to secure domestic water, understanding and mapping renewable and non-renewable groundwater resources, promoting small-scale irrigation and widening the scope of early warning systems and mapping to include access to water.Key words groundwater; climate; Africa; water supply; drought; agriculture Quel impact aura le changement climatique sur les approvisionnements ruraux en eaux souterraines en Afrique? Résumé Une des incertitudes principales concernant les impacts du changement climatique en Afrique est l'effet sur la durabilité des approvisionnements ruraux en eau. Nombre de ces approvisionnements prélèvent dans des nappes souterraines peu épaisses (<50m) et sont l'unique source sûre d'eau potable pour les populations rurales. Les analyses des études existantes de précipitations et de recharge suggèrent que le changement climatique est peu susceptible de conduire à une défaillance catastrophique généralisée des ressources rurales améliorées en eaux souterraines. Ces dernières ne nécessitent que 10 mm de recharge par an pour satisfaire une pompe manuelle, ce qui devrait être réalisable pour une grande partie du continent, bien que 90 millions de personnes puissent être affectés dans des zones marginales de recharge en eaux souterraines (200-500 mm de pluviosité annuelle). Les leçons apprises sur les comportements des ressources souterraines au cours des sécheresses récentes, renforcées par des modélisations hydrogéologi...

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“…The groundwater potential of volcanic rocks varies considerably, reflecting the complexity of the geology. There have been few systematic studies of the hydrogeology of volcanic rocks in Africa, although good site studies are given by Aberra (1990), Vernier (1993), Demlie et al (2007) Kebede et al (2007).…”

Section: Volcanic Rocksmentioning

confidence: 99%

African hydrogeology and rural water supply

MacDonald¹,

Davies²,

Calow³

2008

IAH - Selected Papers on Hydrogeology

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The widespread development of groundwater is the only affordable and sustainable way of improving access to clean water and meeting the Millennium Development Goals for water supply by 2015. Current approaches to rural water supply, in particular demand driven approaches and decentralisation of service delivery have many benefits to the overall efficacy and sustainability of water supplies, however, problems arise when projects do not take into

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Groundwater recharge, flow and hydrogeochemical evolution in a complex volcanic aquifer system, central Ethiopia

Cited by 88 publications

References 18 publications

Importance of Rocks and Their Weathering Products on Groundwater Quality in Central-East Cameroon

Importance of Rocks and Their Weathering Products on Groundwater Quality in Central-East Cameroon

What impact will climate change have on rural groundwater supplies in Africa?

African hydrogeology and rural water supply

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