Weathering in the West Africa Craton: Mineralogy and Geochemistry of Niger River Sediments

The cartographical history of Africa has often left much to the imagination. The idea of a great inland lake along the Niger River in West Africa, for example, has had a rich tradition in written accounts and on maps from Ptolemy onwards. One tendency was to dismiss the notion that any such body of water existed; another was to find divers ways of reconciling tradition and the sparse scattering of new 'facts' that reached European mapmakers. The fundamental problem was ignorance about the hydrology of the interior of Africa, especially in the region of the Niger River. Not until the nineteenth century was the presumed connection between the Niger and Senegal rivers laid to rest, together with the older view that the Niger flowed underground through the eastern highlands to the Nile. Only then was the Niger's actual course established, flowing first east and then, after a great bend, south to debouche into the Gulf of Guinea.1 While the attention of historians focused mostly on the African coastline and the eastern lakes, the early maps of West Africa had regularly showed a prominent inland lake on the southern edge of the Sahara. The cartographical history of this lake has invited further investigation. In this paper we ask how did the image originate, by what physical feature could it have been inspired, and why should it have been considered important in the history of the sub-Saharan region. We approached the issue by looking at four hundred primary maps dating from 900 to 1900. The analysis of this database confirmed that one of the most consistent features throughout the archival record was the image of a lake in West Africa within the region of the middle Niger River.2 From maps on which the lake was named (which was not always the case), we have identified numerous toponyms, including Nigrite Palus, Nilides Palolus, Wangara, Sigisma, Guber, Guarda, Bogs of Guarda, Maberia, Nigris Morass, Dibbie Sea, Lake Dibbie and Lake Debo. This analysis has led to the conclusion that whatever the feature was called, and whatever shape it was given, the mapmakers were each attempting to portray a common physical reality. That entity was the fluctuating area of lakes and branching streams in the middle course of the Niger River, between Djenne and Tombouctou known today as the Inland Niger Delta (Fig. 1). The inland delta, as a unique local feature, is shown on modern maps at best as a limited area of swamp at the southern edge of the Sahara. It is rarely given a name and remains mostly unnoticed in the world's view of modern Africa. Yet, the true meaning of this great wetland lies in the fact that it was once home to a thriving civilization centred on an array of specialized urban settlements near Lake Debo, in the vicinity of modern Djenne (old JenneJeno).3 For more than fifteen hundred years Jenne-Jeno had been the focus of one of the

Research on the implementation of West Africa-North Africa grid interconnection using new electricity-water composite transmission technology

To investigate the spread of Rice yellow mottle virus (RYMV) along the Niger River, regular sampling of virus isolates was conducted along 500 km of the Niger Valley in the Republic of Niger and was complemented by additional sampling in neighbouring countries in West Africa and Central Africa. The spread of RYMV into and within the Republic of Niger was inferred as a continuous process using a Bayesian statistical framework applied previously to reconstruct its dispersal history in West Africa, East Africa, and Madagascar. The spatial resolution along this section of the Niger River was the highest implemented for RYMV and possibly for any plant virus. We benefited from the results of early field surveys of the disease for the validation of the phylogeographic reconstruction and from the well-documented history of rice cultivation changes along the Niger River for their interpretation. As a prerequisite, the temporal signal of the RYMV data sets was revisited in the light of recent methodological advances. The role of the hydrographic network of the Niger Basin in RYMV spread was examined, and the link between virus population dynamics and the extent of irrigated rice was assessed. RYMV was introduced along the Niger River in the Republic of Niger in the early 1980s from areas to the southwest of the country where rice was increasingly grown. Viral spread was triggered by a major irrigation scheme made of a set of rice perimeters along the river valley. The subsequent spatial and temporal host continuity and the inoculum build-up allowed for a rapid spread of RYMV along the Niger River, upstream and downstream, over hundreds of kilometres, and led to the development of severe epidemics. There was no evidence of long-distance dissemination of the virus through natural water. Floating rice in the main meanders of the Middle Niger did not contribute to virus dispersal from West Africa to Central Africa. RYMV along the Niger River is an insightful example of how agricultural intensification favours pathogen emergence and spread.

This paper presents a reconstruction of the palaeodrainage evolution of the Niger River in West Africa in order to contribute to the understanding of sediment supply to the Niger Delta. It has been covered extensively in literature that the Niger River has undergone changes along its course in the Holocene, as implied by the large bend it makes in Mali. However, other enigmatic bends further downstream are indicative of an older and more complicated history that has yet to be understood, and is the focus of this paper. Until now, sediment supply from the Niger River has been considered as being negligible compared to that of the Benue River. The results of this study imply that the contribution from the Niger River was more important than previously thought. The Niger River obtained its present-day geometry in three phases: a Bida Basin phase (Maastrichtian–Miocene); a Iullemmeden Basin phase (Miocene–Pleistocene); and a present-day Niger River phase (Holocene). In the Miocene, an important capture event occurred, increasing the incipient drainage basin by 10 6 km 2 , thereby changing the provenance of the sediment supplied to the Niger Delta from mainly crystalline basement to mixed lithologies including sandstone, shale, limestone and volcanic outcrops.

Textural and geochemical characteristics of the Yikpata river channel sands, Nigeria

Flood is one of the most important natural disasters that cause huge loss of life and properties every year around the world. Moreover, the International Federation of the Red Cross and Red Crescent Societies pointed out that floods were by far the greatest cause of homelessness. In West Africa, many countries are damaged from flooding almost every season. Thus, this study aimed to set a seasonal flood forecast model and carried out an evaluation of the level of risk associated with each seasonal forecast. HEC-RAS (Hydrologic Engineering Centers River Analysis System) was used to develop a hydro-dynamical model of Niger river on a 160km reach (80km upstream to 80kmdownstream of Niamey), then a simple risk measure was used to calculate the probability of overtopping the flood protection dykes in Niamey. Results show that the hydro-dynamical model reproduced well the rating curve over the period 2009-2014. A subsequent copula analysis demonstrated a dependency between flow on the Niger river and flow on the Sirba River, the main tributary contributing to the seasonal flood at Niamey. The Gumbel copula was found to be the best among the tested 5 copulas to represent the dependency between peak flow on the main channel of the Niger River and concomitant flow on the Sirba river. It is found that for the six dykes the probabilities of being overtopped by the flood range from very high (100%) to relatively low (16.67 %) over the 34 years of simulation.

Across West Africa, the River Niger is a major source of freshwater. In addition, the river system also provides services such as aquaculture, transportation, and hydropower. The river network plays a critical role in the hydropolitics and hydroeconomics of the region. Therefore, River Niger is integral to the development of West Africa, hence, there is a need to ensure that the river’s ecosystem is a healthy one. In light of the changing climate and its associated threats such as droughts and floods, constant monitoring and measurements of the the river’s flow system cannot be overemphasized. This study investigates temporal variations in annual river discharge characteristics at eight stations (Koulikoro, Dioila, Kirango, Douna, Mopti, Dire, Ansongo, and Niamey) in the Niger River basin, presenting detailed quantitative findings. Analyzing discharge data of River Niger from 1950 to 1990, the minimum discharge measures (minimum and 10th percentile) exhibit a consistent decreasing trend post-1960, persisting into the 1990s at several stations. Central tendency measures (mean and 50th percentile) also consistently reduced since 1950, with near-zero median values observed in Diola and Douna. Recovery in mean discharge is evident in Ansongo after 1980. Extreme values (maximum and 90th percentile) show decreasing trends across all stations, with some locations exhibiting a slight recovery after 1980. The decreasing trend in annual minimum, mean, and maximum values has implications for water resources, affecting hydroelectric generation, fish farming, and dry season irrigation. Machine learning algorithms (MLAs) are deployed to predict the prediction of monthly river discharge, with LSTM identified as the best-performing model overall. However, model performance varies across locations, with TCN excelling in Diola but underperforming in Koulikoro. This study emphasizes the chaotic nature of time series data and external drivers limiting the long-term predictive capabilities of MLAs. Quantitative evaluation of MLA performance reveals specific strengths and weaknesses at each station. This study underscores the importance of predicting the 10th percentile of annual river discharge for water resource planning. Models exhibit diverse performance across basins, emphasizing the need for tailored approaches. Further analysis considers measures of central tendencies, predicting the 50th percentile (Q50) and mean discharge values. TCN emerges as the best model for Q50 prediction, showcasing superior performance over other models. Additionally, the study delves into predicting high and low extreme discharges, crucial for understanding potential flood events and preparing for meteorological and hydrological droughts. This study concludes by emphasizing the necessity for location-specific studies in the River Niger basin to facilitate an enhanced integrated river management system.

INTRODUCTION : This study presents the results from a meso-inventory conducted in Kebbi State, Northern Nigeria between March and July 2018. We explore he extent to which the farmed-fish value chain is transforming structurally and the roles of capture fishing versus farmed fish. Kebbi is one of Nigeria’s leading states for fish production. Though largely Sudan Savanna (in the north) and Northern Guinea savanna (in the south), and thus semi-arid tropics, there is still a lot of water and a lot of fish. Kebbi’s role in fish production stems from the presence of the longest river in West Africa (River Niger) in the State. River Niger traverses about 374 km within the state. (Raji et al., 2008). Furthermore, the establishment (creation) of Kainji Lake (a reservoir built 1964-68) on the River Niger, with 50% of the surface water in Kebbi State, also facilitated the emergence of fish farming in the state.

Living up to its reputation as a highly variable climate system, the West African Monsoon (WAM) 2012 contrasted strikingly with the previous year. In 2011, the West African rainy season was delayed, patchy, and irregular. In 2012, whilst it was anomalously wet in many area, the Guinea coastal countries and some crucial agricultural regions remained very dry, persisting from the previous year. As a result, 2012 generated the third big food crisis to hit the region in the last seven years. The 2012 WAM forecast, observed climate conditions and the ongoing socio-economic implications for the region are reviewed here.

High-resolution pollen record from core KW31, Gulf of Guinea, documents the history of the lowland forests of West Equatorial Africa since 40,000 yr ago

River Niger is the third-longest river in Africa and the longest river in West Africa. The river basin traverses West and Central African countries, and forms a coastal delta (in southern Nigeria) where it empties into the Atlantic Ocean. The River Niger Basin (RNB) is a crucial asset to development of the West and Central Africa subregions. The RNB ecosystem is currently under heavy degradation of its components due to mutually reinforcing unsustainable socioeconomic development and unregulated urbanization. However, there are limited studies on the pollution of the Lower RNB because of inadequate funding and infrastructure deficit, and existing studies are mainly on the stream tributaries. This paper reviews, for the first time, relevant studies on the Lower RNB and examines the current extent of knowledge regarding the environmental aquatic pollution. We discuss the relevant studies and provide information necessary for management of the basin area.

Nile tilapia (Oreochromis niloticus) is a globally significant aquaculture species rapidly gaining status as a farmed commodity. In West Africa, wild Nile tilapia genetic resources are abundant yet knowledge of fine-scale population structure and patterns of natural genetic variation are limited. Coinciding with this is a burgeoning growth in tilapia aquaculture in Ghana and other countries within the region underpinned by locally available genetic resources. Using 192 single nucleotide polymorphism (SNP) markers this study conducted a genetic survey of Nile tilapia throughout West Africa, sampling 23 wild populations across eight countries (Benin, Burkina Faso, Côte d’Ivoire, Ghana, Togo, Mali, Gambia and Senegal), representing the major catchments of the Volta, Niger, Senegal and Gambia River basins. A pattern of isolation-by-distance and significant spatial genetic structure was identified throughout West Africa (Global FST = 0.144), which largely corresponds to major river basins and, to a lesser extent, sub-basins. Two populations from the Gambia River (Kudang and Walekounda), one from the western Niger River (Lake Sélingué) and one from the upper Red Volta River (Kongoussi) showed markedly lower levels of diversity and high genetic differentiation compared to all other populations, suggesting genetically isolated populations occurring across the region. Genetic structure within the Volta Basin did not always follow the pattern expected for sub-river basins. This study identifies clear genetic structuring and differentiation amongst West African Nile tilapia populations, which concur with broad patterns found in previous studies. In addition, we provide new evidence for fine-scale genetic structuring within the Volta Basin and previously unidentified genetic differences of populations in Gambia. The 192 SNP marker suite used in this study is a useful tool for differentiating tilapia populations and we recommend incorporating this marker suite into future population screening of O. niloticus. Our results form the basis of a solid platform for future research on wild tilapia genetic resources in West Africa, and the identification of potentially valuable germplasm for use in ongoing breeding programs for aquaculture.

Since the adoption of the General Act of Berlin in 1885, which dealt,inter alia, with the Niger River, more agreements have been contracted for the management of some of the shared watercourses in West Africa, particularly in the post-colonial era. Although only six out of its numerous shared watercourses are regulated by legal instruments, West Africa contributed through these agreements to the development of international water prior to the adoption of theunWatercourses and theuneceWater Conventions in the 1990s. Initial instruments dealt primarily with navigation, while later agreements addressed the need for co-operation and incorporated other principles of customary international water law. The two conventions have, no doubt, influenced this trend, raising the question of whether riparian states in West Africa need to be parties to either or both water conventions to enhance management, sharing, and protections of their shared watercourses.

Abstract. This review summarizes the impacts of climate change on runoff in West Africa, assesses the uncertainty in the projections and describes future research needs for the region. To do so, we constitute a meta-database made of 19 studies and 301 future runoff change values. The future tendency in streamflow developments is overall very uncertain (median of the 301 points is 0% and mean +5.2%), except for (i) the Gambia River, which exhibits a significant negative change (median = −4.5%), and (ii) the Sassandra and the Niger rivers, where the change is positive (+14.4% and +6.1%). A correlation analysis revealed that runoff changes are tightly linked to changes in rainfall (R = 0.49), and to a smaller extent also to changes in potential evapotranspiration. Other parameters than climate – such as the carbon effect on plant water efficiency, land use dynamics or water withdrawals – could also significantly impact on runoff, but they generally do not offset the effects of climate change. In view of the potential changes, the large uncertainty therein and the high vulnerability of the region to such changes, there is an urgent need for integrated studies that quantify the potential effects of these processes on water resources in West Africa and for more accuracy in climate models rainfall projections. We especially underline the lack of information concerning projections of future floods and droughts, and of interannual fluctuations in streamflow.

Since the adoption of the General Act of Berlin in 1885, which dealt, inter alia , with the Niger River, more agreements have been contracted for the management of some of the shared watercourses in West Africa, particularly in the post-colonial era. Although only six out of its numerous shared watercourses are regulated by legal instruments, West Africa contributed through these agreements to the development of international water prior to the adoption of the un Watercourses and the unece Water Conventions in the 1990s. Initial instruments dealt primarily with navigation, while later agreements addressed the need for co-operation and incorporated other principles of customary international water law. The two conventions have, no doubt, influenced this trend, raising the question of whether riparian states in West Africa need to be parties to either or both water conventions to enhance management, sharing, and protections of their shared watercourses.