Niger River Basin Research Articles

Water resources planning in the Upper Niger River basin: Are there gaps between water demand and supply?

Study regionThe Upper Niger and Bani River basins in West Africa. Study focusThe growing demand for food, water, and energy led Mali and Guinea to develop ambitious hydropower and irrigation plans, including the construction of a new dam and the extension of irrigation schemes. These two developments will take place upstream of sensible ecosystem hotspots while the feasibility of development plans in terms of water availability and sustainability is questionable. Where agricultural development in past decades focused mainly on intensifying dry-season crops cultivation, future plans include extension in both the dry and wet seasons. New hydrological insights for the regionToday’s irrigation demand corresponds to 7% of the average annual Niger discharge and could account to one third in 2045. An extension of irrigated agriculture is possible in the wet season, while extending dry-season cropping would be largely compromised with the one major existing Sélingué dam. An additional large Fomi or Moussako dam would not completely satisfy dry-season irrigation demands in the 2045 scenario but would reduce the estimated supply gap from 36% to 14%. However, discharge peaks may decrease by 40% reducing the inundated area in the Inner Niger Delta by 21%, while average annual discharge decreases by 30%. Sustainable development should therefore consider investments in water-saving irrigation and management practices to enhance the feasibility of the envisaged irrigation plans instead of completely relying on the construction of a flow regime altering dam.

Projected Changes in Intra-Season Rainfall Characteristics in the Niger River Basin, West Africa

The magnitude and timing of seasonal rainfall is vitally important to the health and vitality of key agro-ecological and social-economic systems of the Niger River Basin. Given this unique context, knowledge concerning how climate change is likely to impact future rainfall characteristics and patterns is critically needed for adaptation and mitigation planning. Using nine ensemble bias-corrected climate model projection results under RCP4.5 and RCP8.5 (RCP—Representative Concentration Pathway) emissions scenarios at the mid-future time period, 2021/2025-2050 from the Coordinated Regional Climate Downscaling Experiments (CORDEX) dataset; this study provides a comprehensive analysis of the projected changes in rainfall characteristics in three agro-ecological zones of the Niger River Basin. The results show an increase in the average rainfall of about 5%, 10–20% and 10–15% for the Southern Guinea, Northern Guinea and Sahelian zones, respectively, relative to the baseline, 1981/1985–2005. On the other hand, the change in future rainfall intensities are largely significant and the frequency of rainfall at the low, heavy and extreme rainfall events in the future decrease at most locations in the Niger River Basin. The results also showed an increase in the frequency of moderate rainfall events at all locations in the basin. However, in the Northern Guinea and Sahel locations, there is an increase in the frequency of projected heavy and extreme rainfall events. The results reveal a shift in the future onset/cessation and a shortening of the duration of the rainy season in the basin. Specifically, the mean date of rainfall onset will be delayed by between 10 and 32 days. The mean onset of cessation will also be delayed by between 10 and 21 days. It is posited that the projected rainfall changes pose serious risks for food security of the region and may require changes in the cropping patterns and management.

Low levels of Plasmodium falciparum genetic diversity in two Nigerian communities bordering the Niger River

Introduction: Extensive genetic diversity of malaria parasites is a major draw back to ongoing control efforts. Population-specific investigation of genetic structure of the parasite is important for effective malaria intervention in endemic populations such as Nigeria where about one-third of the global burden of the disease is borne. This study describes the genetic diversity of Plasmodium falciparum isolates in the Niger River basins, North-Central Nigeria. Methodology: Parasite DNA w as extracted fr om finger -prick blood samples collected from eighty P. falciparum positive individuals. Polymerase Chain Reaction (PCR) genotyping was carried out to target K1, MAD20 and R033 allelic families of Merozoite Surface Protein (MSP) -1 gene and FC27 and 3D7 allelic families of MSP-2 gene. Results: Proportion of isolates with K1 family w as 28(70%) with two alleles in Idah and 16(40%) with two alleles in Ibaji. Proportion of isolates with MAD20 family was 8 (20%) and a total of two alleles were observed in Idah and 4(10%) with two alleles in Ibaji. RO33 proportion was 16 (40%) in Idah one allele and 8(20%) in Ibaji where the allelic family was also observed to be monomorphic. K1 was the most predominant MSP1 allele in the two parasite populations and the frequency of FC27 genotype was higher than 3D7 in both populations. Multiplicity of infection (Mol) with MSP-1 loci was higher in Ibaji (1.30) than Idah (1.05) while MoI with MSP-2 loci was lower in Ibaji (2.00) than Idah (2.13). However, there is no significant difference in the mean Mol between Idah and Ibaji (P > 0.05). The expected heterozygosity (HE) value was 0.56 for MSP-1 and 0.84 for MSP-2. Conclusion: Our findings revealed high levels of monoclonal infections with P. falciparum, suggesting low parasite diversity. This may be a pointer to a reduction in malaria transmission in the river basins.

Infilling Missing Data in Hydrology: Solutions Using Satellite Radar Altimetry and Multiple Imputation for Data-Sparse Regions

In developing regions missing data are prevalent in historical hydrological datasets, owing to financial, institutional, operational and technical challenges. If not tackled, these data shortfalls result in uncertainty in flood frequency estimates and consequently flawed catchment management interventions that could exacerbate the impacts of floods. This study presents a comparative analysis of two approaches for infilling missing data in historical annual peak river discharge timeseries required for flood frequency estimation: (i) satellite radar altimetry (RA) and (ii) multiple imputation (MI). These techniques were applied at five gauging stations along the floodprone Niger and Benue rivers within the Niger River Basin. RA and MI enabled the infilling of missing data for conditions where altimetry virtual stations were available and unavailable, respectively. The impact of these approaches on derived flood estimates was assessed, and the return period of a previously unquantified devastating flood event in Nigeria in 2012 was ascertained. This study revealed that the use of RA resulted in reduced uncertainty when compared to MI for data infilling, especially for widely gapped timeseries (>3 years). The two techniques did not differ significantly for data sets with gaps of 1–3 years, hence, both RA and MI can be used interchangeably in such situations. The use of the original in situ data with gaps resulted in higher flood estimates when compared to datasets infilled using RA and MI, and this can be attributed to extrapolation uncertainty. The 2012 flood in Nigeria was quantified as a 1-in-100-year event at the Umaisha gauging station on the Benue River and a 1-in-50-year event at Baro on the Niger River. This suggests that the higher levels of flooding likely emanated from the Kiri and Lagdo dams in Nigeria and Cameroon, respectively, as previously speculated by the media and recent studies. This study demonstrates the potential of RA and MI for providing information to support flood management in developing regions where in situ data is sparse.

Trends in hydrological extremes in the Senegal and Niger Rivers

In recent years, West Africa has witnessed an increasing number of damaging floods that raise the question of a possible intensification of the hydrological hazards in the region. In this study, the evolution of extreme floods is analyzed over the period 1950–2015 for seven tributaries in the Sudano-Guinean part of the Senegal River basin and four data sets in the Sahelian part of the Niger River basin. Non-stationary Generalized Extreme Value (NS-GEV) distributions including twelve models with time-dependent parameters plus a stationary GEV are applied to annual maxima of daily discharge (AMAX) series. An original methodology is proposed for comparing GEV models and selecting the best for use. The stationary GEV is rejected for all stations, demonstrating the significant non-stationarity of extreme discharge values in West Africa over the past six decades. The model of best fit most commonly selected is a double-linear model for the central tendency parameter (μ), with the dispersion parameter (σ) modeled as either stationary, linear, or a double-linear. Change points in double-linear models are relatively consistent for the Senegal basin, with stations switching from a decreasing streamflow trend to an increasing streamflow trend in the early 1980s. In the Niger basin the trend in μ is generally positive since the 1970s with an increase in slope after the change point, but the change point location is less consistent. The recent increasing trends in extreme discharges are reflected in an especially marked increase in return level magnitudes since the 1980s in the studied Sahelian rivers. The rate of the increase indicated by the study results raises urgent considerations for stakeholders and engineers who are in charge of river basin management and hydraulic works sizing.

Quantifying the Sustainability of Water Availability for the Water-Food-Energy-Ecosystem Nexus in the Niger River Basin.

Water, food, energy, and the ecosystems they depend on interact with each other in highly complex and interlinked ways. These interdependencies can be traced particularly well in the context of a river basin, which is delineated by hydrological boundaries. The interactions are shaped by humans interacting with nature, and as such, a river basin can be characterized as a complex, coupled socioecological system. The Niger River Basin in West Africa is such a system, where water infrastructure development to meet growing water, food, and energy demands may threaten a productive and vulnerable basin ecosystem. These dynamic interactions remain poorly understood. Trade‐off analyses between different sectors and at different spatial scales are needed to support solution‐oriented policy analysis, particularly in transboundary basins. This study assesses the impact of climate and human/anthropogenic changes on the water, energy, food, and ecosystem sectors and characterizes the resulting trade‐offs through a set of generic metrics related to the sustainability of water availability. Results suggest that dam development can mitigate negative impacts from climate change on hydropower generation and also on ecosystem health to some extent.

Prebendalism and Budget Authorization in the Nigerian Legislature

In recent times, the process by which the parliament approves budget estimate from the chief executive has being hijacked by self-serving elements in the National Assembly at the detriment of the masses. Reports abound on how the Nigerian parliament made themselves the highest paid law makers in the whole world, cases of law makers demanding bribes from ministries in which they have oversight functions on have been reported severally. This paper attempts to discuss the effects of the prebendalists on budget authorization, and the means through which they prebendalize during the process of budget authorization in the Nigerian legislature. The paper identified over bloating of budget, neglect in their oversight functions, delay of budget by anti - government forces in the parliament, etc. as the major effects. The paper also revealed that illegal allowances, award/implementation of constituency projects, and padding of budgets through government agencies such as Small and Medium Enterprises Development Agency of Nigeria (SMEDAN), Nigerian Directorate of Employment (NDE), Ogun-Osun River Basin Development Agency (OORBDA), Lower Niger River Basin Development Agency (LNRBDA) and other river basin agencies serve as conduit pipes through which lawmakers prebendalize. Data collection was through secondary sources while content analysis was adopted as a method of analysis. The paper was interrogated using Prebendalism as a framework of analysis. It was recommended that the House of Senate be scrapped and only the House of Representatives retained to save cost. It was also recommended that the Nigerian masses should organize a peaceful protest to the National assembly to demand for an end to self – representation, and finally, a convocation of Sovereign National Conference was suggested to enable Nigerians establish an independent guideline for selecting credible people into leadership positions.

Applications of Open-Access Remotely Sensed Data for Flood Modelling and Mapping in Developing Regions

Flood modelling and mapping typically entail flood frequency estimation, hydrodynamic modelling and inundation mapping, which require specific datasets that are often unavailable in developing regions due to financial, logistical, technical and organizational challenges. This review discusses fluvial (river) flood modelling and mapping processes and outlines the data requirements of these techniques. This paper explores how open-access remotely sensed and other geospatial datasets can supplement ground-based data and high-resolution commercial satellite imagery in data sparse regions of developing countries. The merits, demerits and uncertainties associated with the application of these datasets, including radar altimetry, digital elevation models, optical and radar images, are discussed. Nigeria, located within the Niger river basin of West Africa is a typical data-sparse country, and it is used as a case study in this review to evaluate the significance of open-access datasets for local and transboundary flood analysis. Hence, this review highlights the vital contribution that open access remotely sensed data can make to flood modelling and mapping and to support flood management strategies in developing regions.

Molecular phylogenetic analysis of the catfish species Auchenoglanis occidentalis (Valenciennes, 1840) (Pisces: Claroteidae) from Lake Turkana in East Africa: taxonomic implications

Cytochrome c oxidase subunit I (COI) gene sequences of two specimens here recognized as Auchenoglanis occidentalis from Lake Turkana in the Ethiopian section were determined. A COI gene-based phylogenetic analysis was performed for these along with sequences of African catfish species from the family Clarotidae available in GenBank. Based on results of this analysis, it is concluded that (1) the currently identified A. occidentalis is a species complex that includes several distinct species; (2) the Niger River basin harbors two distinct species of Auchenoglanis, one of which occurs in Lake Turkana, as well as A. biscutatus; and (3) A. sacchii is likely a valid species, but it is not the endemic species of Lake Turkana. It is suggested here that species diversity of Auchenoglanis requires further study based on molecular and morphological evidence.

Modelling blue and green water availability under climate change in the Beninese Basin of the Niger River Basin, West Africa

AbstractThe aim of this study was to quantify climate change impact on future blue water (BW) and green water (GW) resources as well as the associated uncertainties for 4 subbasins of the Beninese part of the Niger River Basin. The outputs of 3 regional climate models (HIRHAM5, RCSM, and RCA4) under 2 emission scenarios (RCP4.5 and RCP8.5) were downscaled for the historical period (1976–2005) and for the future (2021–2050) using the Statistical DownScaling Model (SDSM). Comparison of climate variables between these 2 periods suggests that rainfall will increase (1.7% to 23.4%) for HIRHAM5 and RCSM under both RCPs but shows mixed trends (−8.5% to 17.3%) for RCA4. Mean temperature will also increase up to 0.48 °C for HIRHAM5 and RCSM but decrease for RCA4 up to −0.37 °C. Driven by the downscaled climate data, future BW and GW were evaluated with hydrological models validated with streamflow and soil moisture, respectively. The results indicate that GW will increase in all the 4 investigated subbasins, whereas BW will only increase in one subbasin. The overall uncertainty associated with the evaluation of the future BW and GW was quantified through the computation of the interquartile range of the total number of model realizations (combinations of regional climate models and selected hydrological models) for each subbasin. The results show larger uncertainty for the quantification of BW than GW. To cope with the projected decrease in BW that could adversely impact the livelihoods and food security of the local population, recommendations for the development of adequate adaptation strategies are briefly discussed.

EFFICIENCY OF IRRIGATED AND RAIN-FED RICE (ORYZA SATIVA) PRODUCERS IN FADAMA AGRICULTURE, NIGERIA

SUMMARYGiven the importance of irrigation for rice production, this study compared the technical efficiency of irrigated and rain-fed rice (Oryza sativa) farms in the Upper Niger River Basin and Rural Development Authority (UNRBDA), Nigeria. Primary data were collected from 300 irrigators and 325 rain-fed rice producers. Applying the stochastic frontier Cobb–Douglas production function, net income analysis and Likert scale rating techniques, the study found that irrigated scheme increased marginal factor productivity and profitability. The study revealed the existence of large technical inefficiency in rain-fed farms when compared with irrigated farms. This suggests that there is room for output gains through technical efficiency improvement in the rain-fed system. The mean value of the marginal physical product of inputs (VMPPX) in the irrigated farms (₦2.32) was more than that of rain-fed farm (₦1.67). Thus, if the average producers in the rain-fed are to achieve the technical efficiency level of the average producer in the irrigated farms, they can realize 38% output gains. Similarly, the mean net farm income (NFI) of ₦62,280.00 per ha in the irrigated farm was more than double of that of rain-fed farms ₦22,391.00. The partial regression coefficients for the individual production factors (β1) and (β3) for labour input (X1) and other variable inputs (X3), respectively, were positive and significant at 1% level, suggesting that the partial elasticity of crop output with respect to labour and other costs was higher in the irrigated farms than in the rain-fed farms. The Likert scale rating techniques showed that the poor knowledge of irrigation techniques, insufficient water for irrigation during the dry season, high cost of labour and lack of access to credit were the critical constraints preventing the rain-fed rice producer from joining the irrigation scheme. In view of this, rice irrigators should be encouraged to train more rain-fed farmers on some rudiments of irrigation techniques. They should also be linked to the sources of finance. Water Users Association (WUA) should be established in communities within the scheme areas for effective communication between farmers and the officials of the UNRBDA. Decision on the allocation of resources to Fadama sites including water should be given to WUA to strengthen the membership of the organization, while the government officials serve as supervisory and advisory body.

Assessing floods and droughts in the Mékrou River basin (West Africa): a combined household survey and climatic trends analysis approach

Abstract. The assessment of natural hazards such as floods and droughts is a complex issue that demands integrated approaches and high-quality data. Especially in African developing countries, where information is limited, the assessment of floods and droughts, though an overarching issue that influences economic and social development, is even more challenging. This paper presents an integrated approach to assessing crucial aspects of floods and droughts in the transboundary Mékrou River basin (a portion of the Niger River basin in West Africa), combining climatic trends analysis and the findings of a household survey. The multivariable trend analysis estimates, at the biophysical level, the climate variability and the occurrence of floods and droughts. These results are coupled with an analysis of household survey data that reveals the behaviour and opinions of local residents regarding the observed climate variability and occurrence of flood and drought events, household mitigation measures, and the impacts of floods and droughts. Based on survey data analysis, the paper provides a per-household cost estimation of floods and droughts that occurred over a 2-year period (2014–2015). Furthermore, two econometric models are set up to identify the factors that influence the costs of floods and droughts to impacted households.

Modelling hydrologic and hydrodynamic processes in basins with large semi-arid wetlands

Hydrological and hydrodynamic models are core tools for simulation of large basins and complex river systems associated to wetlands. Recent studies have pointed towards the importance of online coupling strategies, representing feedbacks between floodplain inundation and vertical hydrology. Especially across semi-arid regions, soil-floodplain interactions can be strong. In this study, we included a two-way coupling scheme in a large scale hydrological-hydrodynamic model (MGB) and tested different model structures, in order to assess which processes are important to be simulated in large semi-arid wetlands and how these processes interact with water budget components. To demonstrate benefits from this coupling over a validation case, the model was applied to the Upper Niger River basin encompassing the Niger Inner Delta, a vast semi-arid wetland in the Sahel Desert. Simulation was carried out from 1999 to 2014 with daily TMPA 3B42 precipitation as forcing, using both in-situ and remotely sensed data for calibration and validation. Model outputs were in good agreement with discharge and water levels at stations both upstream and downstream of the Inner Delta (Nash-Sutcliffe Efficiency (NSE) >0.6 for most gauges), as well as for flooded areas within the Delta region (NSE = 0.6; r = 0.85). Model estimates of annual water losses across the Delta varied between 20.1 and 30.6 km3/yr, while annual evapotranspiration ranged between 760 mm/yr and 1130 mm/yr. Evaluation of model structure indicated that representation of both floodplain channels hydrodynamics (storage, bifurcations, lateral connections) and vertical hydrological processes (floodplain water infiltration into soil column; evapotranspiration from soil and vegetation and evaporation of open water) are necessary to correctly simulate flood wave attenuation and evapotranspiration along the basin. Two-way coupled models are necessary to better understand processes in large semi-arid wetlands. Finally, such coupled hydrologic and hydrodynamic modelling proves to be an important tool for integrated evaluation of hydrological processes in such poorly gauged, large scale basins. We hope that this model application provides new ways forward for large scale model development in such systems, involving semi-arid regions and complex floodplains.

Utilizing Process-Based Modeling to Assess the Impact of Climate Change on Crop Yields and Adaptation Options in the Niger River Basin, West Africa

Climate change is estimated to substantially reduce crop yields in Sub-Saharan West Africa by 2050. Yet, a limited number of studies also suggest that several adaptation measures may mitigate the effects of climate change induced yield loss. In this paper, we used AquaCrop, a process-based model developed by the FAO (The Food and Agriculture Organization, Rome, Italy), to quantify the risk of climate change on several key cereal crops in the Niger Basin. The crops analyzed include maize, millet, and sorghum under rain fed cultivation systems in various agro-ecological zones within the Niger Basin. We also investigated several adaptation strategies, including changes in the sowing dates, soil nutrient status, and cultivar. Future climate change is estimated using nine ensemble bias-corrected climate model projection results under RCP4.5 and RCP8.5 (RCP—Representative Concentration Pathway) emissions scenario at mid future time period, 2021/25–2050. The results show that on average, temperature had a larger effect on crop yields so that the increase in precipitation could still be a net loss of crop yield. Our simulated results showed that climate change effects on maize and sorghum yield would be mostly positive (2% to 6% increase) in the Southern Guinea savanna zone while at the Northern Guinea savanna zone it is mostly negative (2% to 20% decrease). The results show that at the Sahelian zone the projected changes in temperature and precipitation have little to no impact on millet yield for the future time period, 2021/25–2050. In all agro-ecological zones, increasing soil fertility from poor fertility to moderate, near optimal and optimal level significantly reversed the negative yield change respectively by over 20%, 70% and 180% for moderate fertility, near optimal fertility, and optimal fertility. Thus, management or adaptation factors, such as soil fertility, had a much larger effect on crop yield than the climatic change factors. These results provide actionable guidance on effective climate change adaptation strategies for rain fed agriculture in the region.

Microbiological quality and biochemical composition of water snail (Pachymelania byronensis) of lower Niger River basin

Microbiological quality and biochemical composition of water snail (Pachymelania byronensis) of lower Niger River basin

Recent Niger Delta shoreline response to Niger River hydrology: Conflict between forces of Nature and Humans

The Niger River Delta is a prolific hydrocarbon province and a mega-delta of economic and environmental relevance. To understand patterns of its recent shoreline evolution (1923–2013) in response to the Niger River hydrology, and establish the role played by forces of Nature and Human, available topographic and satellite remote sensing data, combined with hydro-climatic (rainfall and runoff) data were analyzed.Results indicate that the entire delta coastline dramatically receded: 82% of the >400 km-long coast retreated, during the period 1950–1987; and 69% between 2007 and 2012. Prior to 1950, there was a continuation of seaward advancement along 53–74% of the delta coast. The 1950–1987 shoreline recession coincided with occurrences of two major events in the Niger River basin; these are downward trends in hydro-climatic conditions (the great droughts of the 1970s-1980s), and dam construction on the Lower Niger River at Kainji (1964–1968). The 2007–2012 event corresponded with the extensive channel dredging during 2009–2012 in the Lower Niger River from the coastal town of Warri in the south to Baro in the north. Remarkably, the largest net shoreline advancement recorded in 74% of the entire delta area occurred within a year (2012–2013), which we link to increased sediment supply to the coast caused by the ‘2012’ floods, adjudged the worst floods in the entire Niger River Basin in the last few decades. With both anthropogenic and environmental factors inducing delta evolution, only innovative river and coastal management can determine the fortune of the future coastal development of the Niger Delta.

A coupled modeling framework for sustainable watershed management in transboundary river basins

Abstract. There is a growing recognition among water resource managers that sustainable watershed management needs to not only account for the diverse ways humans benefit from the environment, but also incorporate the impact of human actions on the natural system. Coupled natural–human system modeling through explicit modeling of both natural and human behavior can help reveal the reciprocal interactions and co-evolution of the natural and human systems. This study develops a spatially scalable, generalized agent-based modeling (ABM) framework consisting of a process-based semi-distributed hydrologic model (SWAT) and a decentralized water system model to simulate the impacts of water resource management decisions that affect the food–water–energy–environment (FWEE) nexus at a watershed scale. Agents within a river basin are geographically delineated based on both political and watershed boundaries and represent key stakeholders of ecosystem services. Agents decide about the priority across three primary water uses: food production, hydropower generation and ecosystem health within their geographical domains. Agents interact with the environment (streamflow) through the SWAT model and interact with other agents through a parameter representing willingness to cooperate. The innovative two-way coupling between the water system model and SWAT enables this framework to fully explore the feedback of human decisions on the environmental dynamics and vice versa. To support non-technical stakeholder interactions, a web-based user interface has been developed that allows for role-play and participatory modeling. The generalized ABM framework is also tested in two key transboundary river basins, the Mekong River basin in Southeast Asia and the Niger River basin in West Africa, where water uses for ecosystem health compete with growing human demands on food and energy resources. We present modeling results for crop production, energy generation and violation of eco-hydrological indicators at both the agent and basin-wide levels to shed light on holistic FWEE management policies in these two basins.

GRACE Detected Rise of Groundwater in the Sahelian Niger River Basin

AbstractWest African regions along the Niger River experience climate and land cover changes that affect hydrological processes and therewith the distribution of fresh water resources (WR). This study provides an investigation of long‐term changes in terrestrial water storages (TWS) of the Niger River basin and its subregions by analyzing a decade of satellite gravity data from the Gravity Recovery and Climate Experiment (GRACE) mission. The location of large trends in TWS maps of differently processed GRACE solutions points to rising groundwater stocks. Soil moisture data from a global land surface model allow separating the effect of significantly increasing amount of WR from that of TWS variations. Surface water variations from a global water storage model validated with observations from altimetry data were applied to estimate the groundwater component in WR. For the whole Niger, a rise in groundwater stocks is estimated to be 93 ± 61 km3 between January 2003 and December 2013. A careful analysis of uncertainties in all data sets supports the significance of the groundwater rise. Our results confirm previous observations of rising water tables, indicating that effects of land cover changes on groundwater storage are relevant on basin scales. Areas with rising water storage are stocking a comfortable backup to mitigate possible future droughts and to deliver water to remote areas. This has implications for Niger water management strategies. Increasing groundwater recharges may be accompanied by reduction in water quality. This study helps to inform authority's decision to mitigate its negative impacts on local communities.

Quality of water resources in the Niger basin and in the region of Lagos (Nigeria)

Abstract Water quality studies in Nigeria are usually conducted at local scales and limited to a restricted number of chemical contaminants, while reliable data on trace metal concentrations (including arsenic) are relatively scarce. This study focuses on the quality of available renewable water resources in terms of major ion and trace element concentrations at selected sampling locations in the Lower River Niger basin and part of the Lagos region. A screening of water contamination by arsenic and heavy metals was carried out through water sampling at selected locations using in situ measurement and laboratory testing to estimate heavy metal concentrations and water type. The analysis reveals moderate trace element contamination of the water resources, with the exception of Pb, while Mn and, to a lesser extent, Al exceeded WHO quality standards, but the Arsenic concentrations are within drinking water quality standards and are safe for consumption and irrigation, while the water type is Bicarbonate.

Process refinements improve a hydrological model concept applied to the Niger River basin

AbstractThis study examines a method to improve a process‐oriented hydrological model concept applied to another region than it was first developed for. In principle, we propose to analyse and refine each major hydrological process separately, sequentially, and iteratively. To test the method, the HYPE model concept (HYdrological Predictions for the Environment, originally developed for Sweden) was here applied to the data‐sparse Niger River basin in West Africa. Errors in the baseline Niger‐HYPE model were analysed to identify inadequately described processes. These process descriptions were subsequently isolated and refined through a set of experiments focusing on concept development, input data enhancement, and multivariable calibration. The refinements were guided by in situ discharge observations, earth observations, local expert knowledge, and previous studies. The results show that the original model concept could simulate the annual cycle of discharge, but not the magnitudes or daily dynamics (56‐station average Nash‐Sutcliffe Efficiency = −1). The main processes requiring improved descriptions were precipitation, evaporation, surface runoff, infiltration, soil storage, reservoir regulations, aquifer recharge, and flooding and river‐atmosphere exchange in the Inner Niger Delta. Of these, evaporation, flooding and river‐atmosphere exchange differ so much between Sweden and the Niger River that the model concept had to be refined. All refinements were synthesized in a new model version (Niger‐HYPE2.0) performing significantly better across the basin (56‐station average Nash‐Sutcliffe Efficiency = 0.4). This study demonstrates the danger of applying a model off the shelf, and the obligation to carefully evaluate and revise process descriptions when applying a model concept to a new region. Moreover, the results indicate that our approach to separately, sequentially, and iteratively refine processes together with local experts can substantially improve process‐oriented hydrological models.