Volta Basin Research Articles

River basin organizations in Africa: Volta, Senegal and Inco Maputo River Basin, South Africa

International river basins are covering Africa’s almost 62% of land area. Long history is present in the area of transboundary water management and water law which are partially helpful to regulate rivers (Lautze and Giordano, in submission, 2005).This factled to a range of factors that have driven transboundary water law in Africa in the post-colonial period. Internally, these factors include joint management, water development, and water sharing and division. Externally, they have included a range of factors emanating largely outside the African continent including geopolitics, the concept of hydraulic mission, cultural ties, international environment agendas, and global concern with water conflicts. The results contributed to an evolutionary change in the way these external factors have influenced African transboundary water law. More importantly, analysis of the way internal and external drivers interact suggests that both must be considered by basin states and the outside actors if either is to achieve their objectives (Lautze and Giordano & Borghese, 2005).

Petrography of detrital zircons from sandstones of the Lower Devonian Accraian Formation, SE Ghana: Implications on provenance

Integrated petrographic studies entailing quartz‐type analysis and zircon typologic studies were carried out on sandstones of the Lower Devonian Accraian Formation of southern Ghana to constrain their provenance and tectonic setting. The stratigraphic succession of the Devonian Accraian Group consists mainly of sandstones in the Lower Accraian Formation, shales in the Middle Accraian Formation, and sandstone–shale intercalations in the Upper Accraian Formation. Systematic sampling of sandstones was conducted in the Lower Devonian Accraian Formation. Modal petrographic analysis indicates that the sandstones are quartz arenites with their framework grains consisting on average of, 99.8% quartz, 0.14% lithics with little or no feldspars. They are subangular to subrounded in shape. Modal mineralogy of the sandstones suggests that they are of craton interior origin with an affinity to recycled orogenic provenance. Quartz‐type analysis was used to unravel distinct characteristic features of the quartz grain, namely its polycrystallinity, nonundulose, and undulose nature to constrain the source rock. This pointed to multiple sediment supply from both a plutonic origin and a medium‐ to high‐grade metamorphic terrain. Furthermore, a comprehensive zircon typology study on 298 zircon grains indicate multiple provenances of calc‐alkaline affinity. This study revealed that the Lower Accraian Formation sandstones probably received sediment input from the Paleoproterozoic Birimian Basin granitoids and their associated metasedimentary rocks and some additional supply from the Neoproterozoic sedimentary rocks from the Volta Basin which are inclusive of sediments derived from the Dahomeyide Belt of the Pan‐African Orogeny.

Understanding the physical and human contexts of fluvial floods in rural Ghana

ABSTRACT Major past floods that have resulted in huge losses to households along the Black and White Volta Basins have raised the question of whether they were consequences of climate change or direct anthropogenic activities. This paper therefore examines the physical and human contexts of fluvial floods in rural Central Gonja District of Ghana using the mixed-methods technique. Mann Kendall test was employed to show rainfall trends from 1980 to 2016 supplemented with household surveys and in-depth interviews. The primary data were analysed using IBM SPSS (Version 21) as well as thematic analytical framework. There was no evidence to show that past floods in the district was climate change induced. Results however indicated that floods in Central Gonja District have been the results of a mix of factors including the perennial opening of the Bagre Dam in Neighbouring Burkina Faso, floodplain intrusion and the generally flat topography. The paper thus recommends as a short-term measure an effective collaboration between relevant institutions in Ghana and their counterparts in Burkina Faso for ensuring effective management and use of the shared water resources of the Black and White Volta. An effective flood risk communication, supported by early warning signals is critical in reducing flood disaster losses. In the long-term, however, a relocation of these communities away from the river banks with the support of the District Assembly and other stakeholders will be a welcome alternative.

Untapped Economic Resource Potential of the Neoproterozoic to Early Paleozoic Volta Basin, Ghana: A Review

The ~ 115,000 km2 Volta Basin of Ghana is one of the most studied geological terrains. However, unlike the Birimian and Tarkwaian which have been targeted due to their gold potential, the Volta Basin has been studied largely only toward resolving its lithostratigraphic-related issues. The Volta Basin, however, has economic resource potentials that are worth exploring for the economic benefit of the country. This study seeks to highlight some of the economic resources of the Volta Basin that can be harnessed through further exploration and evaluation. Synthesis of the available literature on the economic resources of the Basin and some few field relations by the authors helped in unraveling the economic resource potential of the Basin. Previous mineral prospectivity maps for various identified minerals in the Basin were merged into a single large-scale map and overlaid on the geology of the area using GIS-based kriging interpolation method to outline the complete mineral resource potential of the Volta Basin. The study reveals that the northeastern, central, and southeastern fringes of the Basin have extensive exposures of sandstones that can be extracted and quarried for construction purposes. The Oti/Pendjari Group with a large areal extent coupled with a great thickness could be evaluated for brick and tiles production. The Group also has a wealth of limestones in the Mamprusi areas that could serve as a hub for cement production to serve all the northern parts of the country if exploited. The Basin could be hosting gold deposits via late hydrothermal fluids evidenced by quartz veins and the presence of extensive continuation of the Birimian structures into the overlying Volta Basin which are the main controlling features of the Birimian gold deposits. The Basin hosts phosphate, bauxite, diamond and iron ore deposits in some localities. Out of these, only iron ore discovered in the Sheini area is currently under exploration but is being constrained by several geological factors. Although Premuasi 1 well has not given promising results on the hydrocarbon potential of the Basin, the lithostratigraphic succession of the basin supports a complete hydrocarbon system just like the Taodeni Basin.

Carbon Isotopes of Riparian Forests Trees in the Savannas of the Volta Sub-Basin of Ghana Reveal Contrasting Responses to Climatic and Environmental Variations

Stable isotopes of tree rings are frequently used as proxies in climate change studies. However, species-specific relationships between climate and tree-ring stable isotopes have not yet been studied in riparian forests in the savannas of West Africa. Four cross-dated discs, each of Afzelia africana Sm. (evergreen) and Anogeissus leiocarpus (DC.) Guill. & Perr. (deciduous) in the humid (HSZ) and dry (DSZ) savanna zones of the Volta basin in Ghana were selected from a larger tree-ring dataset to assess the relationships between the tree-ring carbon isotope composition (δ13C values) and climatic parameters. The atmospherically corrected δ13C values of both studied species showed that A. africana was enriched in 13C compared to A. leiocarpus. Strong correlations were found between δ13C values of A. africana and A. leiocarpus with temperature, but weak correlations with precipitation. Spatial correlation analysis revealed significant relationships between δ13C values of both tree species and Sea Surface Temperatures in the Gulf of Guinea in the southern Atlantic Ocean. The results suggest that the carbon isotope composition of riparian trees in the Volta river basin has a potential to reconstruct climate variability and to assess tree ecological responses to climate change.

Volta basin precipitation and temperature climatology: evaluation of CORDEX-Africa regional climate model simulations

Here, an evaluation of nine simulations of the regional climate models (RCM) performed within the frame of CORDEX-Africa Project to reproduce the Volta Basin climatology (1971–2005) is presented. Performance metrics of climatological means were computed from annual, seasonal, and monthly total values which detect differences in the spatial and temporal structures of the model outputs with observational datasets for precipitation and temperature evaluated over three sub-domains (the Guinea Coast, the Soudano-Sahel, and the Sahel) within the basin. The results reveal pronounced influence of the GCM-derived boundary conditions at homogeneous zones, for example, CNRM-induced model overestimations over the Sahel. A good replica of the spatial distribution of climatic parameters particularly for temperature with biases within 0.1 °C and obvious wet bias for precipitation up to 40% is detected predominantly over the Sahel with widespread differences in spatial extent and intensities. A better performance is obtained for summer and fall but worse in spring for precipitation. The analysis showed that the basic characteristics of the West African climate are reasonably reproduced by the models, including its variability in sign, amplitude, and spatial extent, but also, there are recognized deficiencies of the model simulations for some selected metrics, regions, and seasons. The study emphasizes on individual model skills than in ensemble performance, and CanESM2-RCA4 and NorESM1-RCA4 RCMs were realized to replicate best the observed dataset so these models are recommended for impact studies over the basin for most seasons. Results achieved will be valuable in the choice of GCMs/RCMs for impact study over the basin, and we conclude that this may also depend on the focus of interest, whether it is a study on variability and process representation or region of study or timescales.

Determinants of livelihood strategies of fishing households in the volta Basin, Ghana

The main objective of this study is to identify livelihood strategies of fishing households in response to prevalent vulnerabilities they face within the Volta Basin. Questionnaires were administered to fishery households in the Basin using the multistage sampling technique. A non-hierarchical k-means cluster analysis partitioned the households into four livelihood strategies on which the multinomial logit regression was performed. These four identified strategies are fishery only, fishery and farming, fishery and non-farm, and fishery, non-farming and farming. The results from the multinomial logit regression revealed that marital status of head of household, number of months of food shortage experienced by a household per year, access to credit, access to extension services, distance to regular markets and district capital as well as experience in fishery were the major determinants of livelihood strategies. Implications for policy include the need for public extension services and training to invigorate fishery households’ income. As majority of the fishery households combined fishing and non-fishing strategies, livelihood intervention programmes should prioritize improvement of the non-fishing activities and lead to opening other opportunities for rural development. This will take pressure off the fish stock by facilitating the regeneration of fish stock.

Recent climate trends for the Volta Basin in West Africa

WeatherVolume 74, Issue S1 p. S13-S22 Research Article Recent climate trends for the Volta Basin in West Africa Deborah Darko, Corresponding Author Deborah Darko deborah.ofori@gmail.com orcid.org/0000-0002-3378-5129 Civil Engineering Department, Kwame Nkrumah University of Science and Technology, University Post Office, Kumasi, Ghana Water Research Institute, Council for Scientific and Industrial Research, Accra, GhanaCorrespondence to: D. Darkodeborah.ofori@gmail.comSearch for more papers by this authorKwaku A. Adjei, Kwaku A. Adjei Civil Engineering Department, Kwame Nkrumah University of Science and Technology, University Post Office, Kumasi, GhanaSearch for more papers by this authorSamuel N. Odai, Samuel N. Odai Civil Engineering Department, Kwame Nkrumah University of Science and Technology, University Post Office, Kumasi, GhanaSearch for more papers by this authorEmmanuel Obuobie, Emmanuel Obuobie Water Research Institute, Council for Scientific and Industrial Research, Accra, GhanaSearch for more papers by this authorRuby Asmah, Ruby Asmah Water Research Institute, Council for Scientific and Industrial Research, Accra, GhanaSearch for more papers by this authorDennis Trolle, Dennis Trolle Department of Bioscience, Aarhus University, Silkeborg, DenmarkSearch for more papers by this author Deborah Darko, Corresponding Author Deborah Darko deborah.ofori@gmail.com orcid.org/0000-0002-3378-5129 Civil Engineering Department, Kwame Nkrumah University of Science and Technology, University Post Office, Kumasi, Ghana Water Research Institute, Council for Scientific and Industrial Research, Accra, GhanaCorrespondence to: D. Darkodeborah.ofori@gmail.comSearch for more papers by this authorKwaku A. Adjei, Kwaku A. Adjei Civil Engineering Department, Kwame Nkrumah University of Science and Technology, University Post Office, Kumasi, GhanaSearch for more papers by this authorSamuel N. Odai, Samuel N. Odai Civil Engineering Department, Kwame Nkrumah University of Science and Technology, University Post Office, Kumasi, GhanaSearch for more papers by this authorEmmanuel Obuobie, Emmanuel Obuobie Water Research Institute, Council for Scientific and Industrial Research, Accra, GhanaSearch for more papers by this authorRuby Asmah, Ruby Asmah Water Research Institute, Council for Scientific and Industrial Research, Accra, GhanaSearch for more papers by this authorDennis Trolle, Dennis Trolle Department of Bioscience, Aarhus University, Silkeborg, DenmarkSearch for more papers by this author First published: 12 December 2018 https://doi.org/10.1002/wea.3303Citations: 3Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume74, IssueS1December 2019Pages S13-S22 RelatedInformation

Nutritional composition of aquatic plants and their potential for use as animal feed: A case study of the Lower Volta Basin, Ghana

Etse WJ, Annang T, Ayivor JS. 2018. Nutritional composition of aquatic plants and their potential for use as animal feed: a case study of the Lower Volta Basin, Ghana. Biofarmasi J Nat Prod Biochem 9: 99-112. The study was conducted to determine the nutritional composition of selected dominant aquatic plants and their significant effect on the chemical and physical characteristics of the water. Aquatic plants namely Nymphaea lotus, Typha australis, Ipomoea aquatica, and Scirpus cubensis were collected, identified and authenticated at the Ghana Herbarium. The proximate nutritional compositions of these plants were measured using the standard procedure outlined in the Association of Official Analytical Chemist (AOAC 2002). Water and sediment quality analyses of some physicochemical variables were also carried out using processes described in the standard methods for water and wastewater examination. The results showed that nutrient composition such as the crude protein, ether extracts, ash content, and nitrogen-free extracts was significantly higher than the corresponding constituents in Panicum maximum used as a control for the study. The findings also indicated that levels of heavy metals in all plants fell within the WHO/FAO standards for metals in vegetables and food. The effects of the physicochemical parameter of water also revealed that pH, nitrate, turbidity, DO, and BOD levels were found significantly different from the control site. The level of heavy metal in the sediment samples revealed significant variations in the distribution of the metals, with Zn showing the most significant difference and Pb the least with a mean level of 7.5±0.86 mg/L and 0.4±0.03 mg/L respectively. These plant species suggests having a high nutritive potential and indicates their possible use as mixed ingredients in animal feed. Exploitation of these aquatic plants for animal feed would be a step towards better utilization of these plants help in the management of aquatic plants within the basin.

Projected increased risk of water deficit over major West African river basins under future climates

Estimating climate change impacts on water resources in West Africa has been challenged by hydrological data scarcity and inconsistencies in the available climate projections. In this study, multi-model ensembles of the most recent global and regional climate models output are used to simulate the hydrologic impacts of climate change in five major river basins (i.e. Senegal, Gambia, Volta, Niger and Chad) that comprise most of West Africa. Under Representative Concentration Pathways 4.5 and 8.5, the results consistently project substantial decreases (10 to 40%) in potential water availability across the five major river basins. The largest changes are projected to occur in the Senegal basin, Gambia basin and the Sahelian part of the other river basins. The negative trends are steepest after 2050 and in the higher greenhouse gas forcing scenario. Therefore, in a business-as-usual world, reduced water availability combined with the region’s rapidly growing population will have West Africa facing an unprecedented water deficit during the second half of the twenty-first century. However, greenhouse gas mitigation can help reduce this deficit. In the Volta basin, although potential water availability declines considerably, precipitation exceeds potential evapotranspiration during the monsoon season in both forcing scenarios, suggesting opportunities for adaptation.

Assessment of Spatio-Temporal Changes of Land Use and Land Cover over South-Western African Basins and Their Relations with Variations of Discharges

West African basins play a vital role in the socio-economic development of the region. They are mostly trans-boundary and sources of different land use practices. This work attempts to assess the spatio-temporal land use and land cover changes over three South Western African basins (Volta, Mono and Sassandra basins) and their influence on discharge. The land use and land cover maps of each basin were developed for 1988, 2002 and 2016. The results show that all the studied basins present an increase in water bodies, built-up, agricultural land and a decline in vegetative areas. These increases in water bodies and land use are as a result of an increase in small reservoirs, of dugouts and of dam constructions. However, the decline in some vegetative clusters could be attributed to the demographic and socio-economic growth as expressed by the expansion of agriculture and urbanization. The basic statistical analysis of precipitation and discharge data reveals that the mean annual discharge varies much more than the total annual precipitation at the three basins. For instance, in the entire Volta basin, the annual precipitation coefficient of variation (CV) is 10% while the annual discharge CV of Nawuni, Saboba and Bui are 43.6%, 36.51% and 47.43%, respectively. In Mono basin, the annual precipitation CV is 11.5% while the Nangbeto and Athieme annual discharge CV are 37.15% and 46.60%, respectively. The annual precipitation CV in Sassandra basin is 7.64% while the annual discharge CV of Soubre and Dakpadou are 29.41% and 37%, respectively. The discharge varies at least three times much more than the precipitation in the studied basins. The same conclusion was found for all months except the driest months (December and January). We showed that this great variation in discharge is mainly due to land use and land cover changes. Beside the hydrological modification of the land use and land cover changes, the climate of the region as well as the water quality and availability and the hydropower generation may be impacted by these changes in land surfaces conditions. Therefore, these impacts should be further assessed to implement appropriate climate services and measures for a sustainable land use and water management.

Toward an integrated watershed zoning framework based on the spatio-temporal variability of land-cover and climate: Application in the Volta river basin

This article details a watershed regionalization approach which uses the concept of entropy in combination with the k-means clusters analysis. The regionalization approach aims to subdivide a watershed into relatively uniform zones based on the spatial variability of the local climate and land-covers. A case study is presented to illustrate the approach and outline the environmental implications of the outcomes. Especially, the study reports an application in the Volta river basin which is a transnational watershed, shared by six different countries in West Africa. Over years, the transboundary status of the Volta watershed seems to have exacerbated its environmental challenges, because the environmental policies in the six countries do not necessarily complement. Subsequently, it is desirable to envision unified scientific tools to support the management platform of the Volta basin. To date, the literature on the Volta has virtually neglected this aspect. Hence, this case study is timely as it intends to create a unified zoning system for the Volta river basin. In the study, formulations of entropy theory and k-means clustering were jointly applied to 16-years gridded time-series of monthly leaf area index, precipitation, and temperature across the Volta basin. Based on a clustering optimization criterion, a total of five zones were identified then the related land-cover and climatic patterns were comparatively analyzed. Significant environmental contrasts were diagnosed then specificities were pinpointed for each zone. A comparison of the new zones with an existing macro-scale ecoregion shows similarities which sustain the capacity of the regionalization approach to capturing meaningful biophysical signals. Hence, the zoning technique may be valued for further applications in environmental management.

U–Pb detrital zircon ages of sediments from the Firgoun and Niamey areas (eastern border of West African Craton, West Niger)

This study uses field observations and new U–Pb ages of detrital zircon grains from three samples to question the stratigraphic position of the Firgoun and Niamey siliciclastic sediments, presumed to be Neoproterozoic in age. Sharing several lithological similarities with the Late Cryogenian “Triad” of the Taoudenni, Gourma, and Volta basins, the uppermost siliciclastic sediments of the Firgoun and Niamey areas were likely also deposited during this period. This is corroborated by matrix-supported diamictites with faceted or striated pebbles as well as by structures resembling cryoturbation processes. However, the detrital zircon U–Pb age record that we present here for the lowermost deposits of Firgoun and Niamey provides mainly Paleoproterozoic ages, and very few Archean ages, altogether in a range from 1822±9 to 3392±9 Ma. Therefore, the new data only show that the Firgoun and Niamey sediments were deposited before about 1800 Ma. Nevertheless, the U–Th–Pb zircon age data allows examining the possible provenance of the sediments. We show that the latter was likely in the westerly close vicinity of the studied areas. The Archean zircons are likely inherited, and possibly originating from a more westerly source. The nearby source of the Niamey and Firgoun sediments suggests that a high topographic relief was still existing in the south-central part of the West African Craton in the Mid Neoproterozoic.

Evaluation of CMIP5 Global Climate Models over the Volta Basin: Precipitation

A selected number of global climate models (GCMs) from the fifth Coupled Model Intercomparison Project (CMIP5) were evaluated over the Volta Basin for precipitation. Biases in models were computed by taking the differences between the averages over the period (1950–2004) of the models and the observation, normalized by the average of the observed for the annual and seasonal timescales. The Community Earth System Model, version 1-Biogeochemistry (CESM1-BGC), the Community Climate System Model Version 4 (CCSM4), the Max Planck Institute Earth System Model, Medium Range (MPI-ESM-MR), the Norwegian Earth System Model (NorESM1-M), and the multimodel ensemble mean were able to simulate the observed climatological mean of the annual total precipitation well (average biases of 1.9% to 7.5%) and hence were selected for the seasonal and monthly timescales. Overall, all the models (CESM1-BGC, CCSM4, MPI-ESM-MR, and NorESM1-M) scored relatively low for correlation (<0.5) but simulated the observed temporal variability differently ranging from 1.0 to 3.0 for the seasonal total. For the annual cycle of the monthly total, the CESM1-BGC, the MPI-ESM-MR, and the NorESM1-M were able to simulate the peak of the observed rainy season well in the Soudano-Sahel, the Sahel, and the entire basin, respectively, while all the models had difficulty in simulating the bimodal pattern of the Guinea Coast. The ensemble mean shows high performance compared to the individual models in various timescales.

Modelling streamflow response to climate change in data-scarce White Volta River basin of West Africa using a semi-distributed hydrologic model

Abstract This study uses high resolution Climate Forecast System Reanalysis (CFSR), SWAT and two IPCC climate change (CC) scenarios (A1B and B1) combined with two general circulation models (GCMs) (HADCM3 and MPEH5) to evaluate impact of CC on streamflow in the White Volta basin of West Africa. The evaluation criteria (R2 and NSE > 0.70 and PBIAS within ±25%) during calibration and validation showed good simulation of the basin hydrology. Using average streamflow from 1979 to 2008 as a baseline, there were uncertainties over the sign of variation of annual streamflow in the 2020s. Annually, streamflow change is projected to be within −4.00% to +13.00% in the 2020s and +3.00% to +16.00% in the 2050s. Monthly streamflow changes for most months vary between −13.00% and +32.00%. A shift in monthly maximum streamflow from September to August is projected, while the driest months (December, January and February) show no change in the future. Based on the model results, the White Volta basin will likely experience an increase in streamflow by the mid-21st century. This would call for appropriate investment into cost-effective adaptive water management practices to cater for the likely impact of CC on the future hydrology of the basin.

Simulation of climate characteristics and extremes of the Volta Basin using CCLM and RCA regional climate models

The extent to which statistical bias-adjusted outputs of two regional climate models alter the projected change signals for the mean (and extreme) rainfall and temperature over the Volta Basin is evaluated. The outputs from two regional climate models in the Coordinated Regional Climate Downscaling Experiment for Africa (CORDEX-Africa) are bias adjusted using the quantile mapping technique. Annual maxima rainfall and temperature with their 10- and 20-year return values for the present (1981–2010) and future (2051–2080) climates are estimated using extreme value analyses. Moderate extremes are evaluated using extreme indices (viz. percentile-based, duration-based, and intensity-based). Bias adjustment of the original (bias-unadjusted) models improves the reproduction of mean rainfall and temperature for the present climate. However, the bias-adjusted models poorly reproduce the 10- and 20-year return values for rainfall and maximum temperature whereas the extreme indices are reproduced satisfactorily for the present climate. Consequently, projected changes in rainfall and temperature extremes were weak. The bias adjustment results in the reduction of the change signals for the mean rainfall while the mean temperature signals are rather magnified. The projected changes for the original mean climate and extremes are not conserved after bias adjustment with the exception of duration-based extreme indices.

Streamflow response under different climate change scenarios in data-scarce White Volta basin of West-Africa using a semi-distributed hydrologic model

In this study, streamflow response in White Volta basin of West Africa was evaluated using ECHAM5 (MPEH5) GCM for two IPCC climate change scenarios (A1B and B1) and semi-distributed hydrologic model (SWAT) for three future time periods; 2020s, 2050s and 2080s using 1987-1996 as baseline. Both climate change scenarios project decrease in rainfall in 2020s but increases in 2050s and 2080s. Decrease in rainfall in 2020s was higher in B1 scenario compared to A1B; whereas for 2050s and 2080s, increases in rainfall were higher in A1B scenario than B1. Projected average changes indicate that overall the climate will be warmer and wetter in future. Projected annual streamflow volumes show disproportionate change (~220%) in response to slight changes in mean annual rainfall. Streamflow volume shows sharp changes for A1B scenario than B1 in 2020s whilst in 2050s and 2080s, the changes are moderate. Projected average annual streamflow changes are -3.1% in 2020s, 5.1% in 2050s and 13.3% in 2080s. Overall projected streamflow changes for both A1B and B1 scenarios were not so dramatic (less than ±20%). These call for adaptation strategies to reduce vulnerability and ensure water security within the basin.

Provenance of shales and sandstones from the Devonian Accraian Group, southern Ghana

Petrographic and whole rock geochemical studies were carried out on sandstones and shales of the Devonian Accraian Group of southern Ghana to constrain their provenance and tectonic setting. Modal petrographic analysis on the sandstones show that the framework grains are sub-angular to rounded in shape. Upper continental crust normalized multi-element plots, as well as trace element ratios, suggests that the sandstones and shales were mainly derived from felsic and recycled sources. Modal mineralogy of the sandstones, and major and trace element geochemistry of sandstones and shales further suggest that they are of recycled orogenic provenance. Discriminant function based major-element diagram suggests that the Accraian sandstones and shales were deposited in a Passive margin setting. Weathering indices suggest high degree of source area weathering. It is of the view that the Accraian sandstones and shales, most probably, received sediment input mostly from the Paleoproterozoic Birimian metasedimentary rocks and their associated granitoids and/or the Neoproterozoic sedimentary rocks from the Volta Basin which are both positioned northwest and north, respectively, of the Accraian sedimentary rocks.

Modeling future flows of the Volta River system: Impacts of climate change and socio-economic changes

As the scientific consensus concerning global climate change has increased in recent decades, research on potential impacts of climate change on water resources has been given high importance. However in Sub-Saharan Africa, few studies have fully evaluated the potential implications of climate change to their water resource systems. The Volta River is one of the major rivers in Africa covering six riparian countries (mainly Ghana and Burkina Faso). It is a principal water source for approximately 24 million people in the region. The catchment is primarily agricultural providing food supplies to rural areas, demonstrating the classic water, food, energy nexus. In this study an Integrated Catchment Model (INCA) was applied to the whole Volta River system to simulate flow in the rivers and at the outlet of the artificial Lake Volta. High-resolution climate scenarios downscaled from three different Global Climate Models (CNRM-CM5, HadGEM2-ES and CanESM2), have been used to drive the INCA model and to assess changes in flow by 2050s and 2090s under the high climate forcing scenario RCP8.5. Results show that peak flows during the monsoon months could increase into the future. The duration of high flow could become longer compared to the recent condition. In addition, we considered three different socio-economic scenarios. As an example, under the combined impact from climate change from downscaling CNRM-CM5 and medium+ (high economic growth) socio-economic changes, the extreme high flows (Q5) of the Black Volta River are projected to increase 11% and 36% at 2050s and 2090s, respectively. Lake Volta outflow would increase +1% and +5% at 2050s and 2090s, respectively, under the same scenario. The effects of changing socio-economic conditions on flow are minor compared to the climate change impact. These results will provide valuable information assisting future water resource development and adaptive strategies in the Volta Basin.

Hydro-climatic stress, shallow groundwater wells and coping in Ghana's White Volta basin

Debates of the nexus between water-related stresses and water availability for groundwater-dependent irrigation which comprises of non-conventional groundwater abstraction schemes is only recently emerging. The interaction between Seasonal Shallow Wells (SSWs), one of such indigenous abstractions scheme and groundwater recharge remains new to groundwater science and development. The SSWs supplement formal irrigation (e.g. reservoirs) and surface water for dry season agriculture in Ghana's White Volta Basin, yet links with the overall gradient of groundwater is unknown. Therefore, using the Water Evaluation And Planning (WEAP) model and qualitative techniques, the implications of groundwater recharge and surface runoff in their orientation to shallow wells is explored. Standardized precipitation index (SPI) from a regional downscale model for droughts and floods showed increased drought and flood influence on groundwater recharge and irrigation. Enhanced surface runoff water and climate change continuously reduced groundwater recharge by 2030, with decreased stream and water inflows. Irrigation water requirements of reservoirs were computed to be between 173% and 327% of normal reservoir water requirements, yet majority of dams did not meet these requirements especially during the dry season. The basin has history of dryness and exhibited uneven distribution of groundwater, yet recharged water of unsaturated soil moisture zones made water available to the SSWs. The SSWs were patronised mostly by women and farming households based on perceptions of limited cost, less sophistication and no formal regulatory measures. The paper therefore provides framework for establishing links between the mechanics of SSWs, and existing climatic and hydrologic conditions for informed groundwater development.