Niger River Basin Research Articles

Appraising meteoric-surface-groundwater interaction through analyses of hydrochemical evolution of water resources in the Lower Niger River Basin, Nigeria

Appraising meteoric-surface-groundwater interaction through analyses of hydrochemical evolution of water resources in the Lower Niger River Basin, Nigeria

Enhancing Disaster Response and Resilience Through Near-Time GIS for Flood Monitoring and Analysis in Niger River Basin, Nigeria

Enhancing Disaster Response and Resilience Through Near-Time GIS for Flood Monitoring and Analysis in Niger River Basin, Nigeria

Nitrogen use efficiency of open-pollinated maize cultivars and topcrosses under low nitrogen soil

The study was conducted to evaluate the nitrogen utilization efficiency (NUE) of open-pollinated maize cultivars under low nitrogen soil conditions. It took place at the Lower Niger River Basin Development Authority in Ilorin, Nigeria, during the 2019 and 2020 cropping seasons. The nitrogen treatments (0, 45, and 90 kg N ha⁻1) were assigned as the main plots, while the genotypes were designated as sub-plots in a split-plot design. The NUE of open-pollinated varieties (OPVs) and Topcrosses significantly increased with the application of 45 kg of nitrogen per hectare compared to 0 kg. Similarly, the maize grain yield for both OPVs and Topcrosses ranged from 1.40 to 3.57 t ha⁻1 and from 1.07 to 2.64 t ha⁻1 across the two years with the application of 45 kg of nitrogen per hectare compared to 0 kg. With the exception of days to 50 % silking, all other traits tested exhibited a significant correlation with grain yield. A gene pool for tolerance to low nitrogen may have been present in the cultivars Dmr-Esr Y Cif 2 and Acr 95 Tze Comp 4C3, which combined well with other cultivars to produce high grain yield and NUE. Topcrosses, including Ev Dt-Y 2000 Str C0 × Tze-W Dt Str C4, Dmr-Esr Y Cif 2 × Acr 95 Tze Comp 4C3, Ak 95 Dmr-Esrw × Tzb Rel D4 CO-W, Dmr-Esr Y Cif 2 × Tze-W Dt Str C4, and Br 9922 Dmr Sr × Ev Dt-Y 2000 Str C0, also demonstrated strong potential for maize grain yield and NUE. This suggests that these crosses could serve as promising candidates for developing low nitrogen tolerance in maize for low nitrogen soil environments. A positive relationship between fertilizer levels, NUE, and grain yield indicates that proper nitrogen fertilizer management can enhance both NUE and the grain yield of maize genotypes. Genetic analysis revealed that both phenotypic coefficient of variation (PCV) and environmental variance (δ2p) were higher than genotypic coefficient of variation (GCV) and genetic variance (δ2g), suggesting that environmental influences were more significant than genetic factors for the tested traits. Consequently, improving these traits may be achieved by manipulating environmental conditions.

Assessment of Agricultural Drought Using Vegetation Condition Index and Vegetation Health Index in Niger River Basin, Nigeria

Soil moisture indicates the dryness of the ground surface. This phenomenon is directly tied to vegetation quality and Land Surface Temperature in a specific place. As a result, these characteristics indirectly describe the dryness of the ground surface. This study assessed agricultural drought in Niger River in Nigeria. Data used include MODIS driven MOD13Q1 (NDVI), and MOD11A2 (LST) datasets obtained from Land Processes Distributed Active Archive Center. These datasets were used to compute Vegetation Condition Index (VCI) and Vegetation Health Index (VHI) in Niger River Basin, Nigeria. Additionally, correlation and regression analyses were used to check the relationship between LST and NDVI. Results revealed that the mean NDVI for the year 2002 is 0.494, 0.477 in 2007, 0.468 in 2012, 0.458 in 2017 and 0.430 in 2022. The mean LST in Niger River Basin for year 2002 is 32.28 oC, 32.12 oC in 2007, 32.35 oC in 2012, 33.20 oC in 2017 and 33.41 oC in 2022. For the statistical relationship between NDVI and LST, results exhibited negative correlation, with -0.33 in 2002, -0.43 in 2007, -0.42 in 2012, -0.36 in 2017 and -0.27 in 2022. For the VCI results, findings revealed that the mean VCI in the basin was 83.73 in 2002, 64.26 in 2007, 56.76 in 2012, 45.32 in 2017, and 14.93 in 2023. Also, the VHI results revealed that the mean VHI in the basin was 75.44 in 2002, 69.54 in 2007, 61.02 in 2010, 37.22 in 2017 and 18.87 in 2022. The study therefore concluded that vegetation is decreasing in the basin, while land surface temperature is increasing.

Integrated assessment of flood susceptibility and exposure rate in the lower Niger Basin, Onitsha, Southeastern Nigeria

BackgroundVarious methods have been utilized to investigate and mitigate flood occurrences, yet there is a paucity of literature on factors, such as soil compositions, that contribute to persistent flooding in river basins like the Lower Niger catchment, specifically at Onitsha. Furthermore, the study seeks to furnish essential geospatial data concerning flood vulnerability, flood risks, and exposure rates in the Lower Niger Catchment area, situated in Onitsha, southeastern Nigeria.Materials and methodsSoil samples were collected from 10 specific locations identified through GPS and ground-truthing techniques. Additionally, satellite imagery from the Landsat Enhanced Thematic Mapper (ETM +) was utilized, with supervised classification employed to extract feature classes. Analysis operations were conducted using IDRISI software, resulting in the creation of digital elevation models (DEMs), susceptibility maps, and flood-risk zones.ResultsAnalysis revealed that the predominant soil composition in the study area comprises sandy (84.8%), silt (8.1%), and clayey (7.1%) soils. Utilizing these soil characteristics alongside relevant aerial data, exposure rates were determined at various scales to delineate the most flood-vulnerable zones in the basin. It was found that certain areas, accommodating a population exceeding 79,426 across 2,926.2 ha, were particularly susceptible to flooding. Notably, major markets such as Bridgehead, Textile, and Biafra were identified as highly susceptible, with varying degrees of risk. The prevalence of sandy soil, which facilitates increased rainwater infiltration but is also prone to rapid saturation and runoff, likely contributes to the heightened susceptibility to flooding in these areas.ConclusionGeospatial analysis employing remote sensing data indicates the high susceptibility and exposure to flooding in the lower Niger River Basin around Onitsha. Urgent mitigation efforts are imperative, necessitating the establishment of zoned areas equipped with effective drainage systems to safeguard vulnerable populations.

Contribution of Saharan dust to chemical weathering fluxes and associated phosphate release in West Africa

Huge amounts of mineral dust are produced in northern Africa, representing the largest source of aerosols worldwide. Transatlantic dust transport is known to fertilize soils as far as in the Amazon Basin. Yet, the influence of Saharan dust on chemical weathering fluxes and associated nutrient release in West Africa remains largely overlooked. To address this issue, we analysed clay fractions (<2 µm) of river sediments (n = 37) from across the Niger River basin - the largest river system in West Africa - using neodymium and hafnium isotope compositions as proxies for provenance (εNd) and chemical weathering (ΔεHf CLAY).Compared to previously published data for corresponding sand fractions, measured εNd values indicate significant size-dependent decoupling for Nd isotopes in most samples, with εNd differences between clay and sand fractions yielding values as great as ∼26 ε-units. Using mixing models, we show that this discrepancy reflects the overwhelming presence in the studied clay fractions of Harmattan dust blown from the Bodélé Depression in Chad, which we estimate to account for about 40 % of the fine-grained sediment load exported to the Gulf of Guinea. Additionally, significant ΔεHf CLAY variability occurs across the Niger catchment, partly explained by the presence of zircon in clay-size fractions, but also by preferential alteration of dust-borne accessory phosphate minerals in the subtropical regions of the watershed.Based on these results, we propose that Saharan dust plays a major role in controlling regional patterns of chemical weathering in West Africa, suggesting that enhanced wet deposition of mineral dust in shield areas dominated by transport-limited weathering regime can result in a large increase in weatherability and associated release of phosphorus. These findings have general implications for the importance of mineral aerosols in controlling sediment yield and the supply of weathering-derived nutrients to continental areas bordering large subtropical deserts worldwide.

Flood frequency analysis of Asa River, Ilorin, Nigeria

Flooding poses a risk to human lives, livelihoods, infrastructure, and the environment. Therefore, understanding the flood frequency patterns of the Asa River is crucial in developing effective flood management strategies. This study explores the statistical technique to understand the nature and magnitude of high discharge of floods in the Asa River, aiming at relating the magnitude of floods and their frequency of occurrence through probability distribution. The Gumbel Extreme Value Distribution method was used to analyze the 30 years (1991-2020) flood discharge data of River Asa which was collected from Lower Niger River Basin and Development Authority, Ilorin, and flood discharge for the return periods of 5 years, 10 years, 20 years, 30 years, 50 years, 100 years, and 150 years, was predicted. From the observations of Gumbel’s distribution, the R2 value acquired from the trend line equation was 0.9227, indicating that Gumbel's extreme value distribution is suitable for estimating predicted river flood flow. The expected flood discharge for the return periods of the upcoming 5 years, 10 years, 15 years, 20 years, 25 years, 50 years, 100 years, and 150 years, was estimated to be 43.19 m3/s, 51.12 m3/s, 55.60 m3/s, 58.73 m3/s, 63.11 m3/s, 68.58 m3/s, 75.96 m3/s, and 80.27m3/s respectively. The results obtained in this research would adequately serve as a planning guide for the decision makers on the development and flood risk management along Asa River, to achieve sustainable development and management, with a view of protecting lives and properties downstream of the watershed.

Combined impacts of climate and land-use change on future water resources in Africa

Abstract. Africa depends on its water resources for hydroelectricity, inland fisheries and water supply for domestic, industrial and agricultural operations. Anthropogenic climate change (CC) has changed the state of these water resources. Land use and land cover have also undergone significant changes due to the need to provide resources to a growing population. Yet, the impact of the land-use and land cover change (LULCC) in addition to CC on the water resources of Africa is underexplored. Here we investigate how precipitation, evapotranspiration (ET) and river flow respond to both CC and LULCC scenarios across the entire African continent. We set up a Soil and Water Assessment Tool (SWAT+) model for Africa and calibrated it using the hydrological mass balance calibration (HMBC) methodology detailed in Chawanda et al. (2020a). The model was subsequently driven by an ensemble of bias-adjusted global climate models to simulate the hydrological cycle under a range of CC and LULCC scenarios. The results indicate that the Zambezi and the Congo River basins are likely to experience reduced river flows under CC with an up to 7 % decrease, while the Limpopo River will likely have higher river flows. The Niger River basin is likely to experience the largest decrease in river flows in all of Africa due to CC. The Congo River basin has the largest difference in river flows between scenarios with (over 18 % increase) and without LULCC (over 20 % decrease). The projected changes have implications for the agriculture and energy sectors and hence the livelihood of people on the continent. Our results highlight the need to adopt policies to halt global greenhouse gas emissions and to combat the current trend of deforestation to avoid the high combined impact of CC and LULCC on water resources in Africa.

STREAMFLOW GENERATION OF RIVER NIGER BASIN KOGI USING MODIFIED THOMAS FIERRING MODEL

There is a concerted effort towards protection of environment as a result of incessant change of climate and its resultant effects on human live and property. Studies have shown that flooding is ranked the most devastating natural disaster in the world; and it is a common natural environmental hazard in various parts of Nigeria. In recent times, flooding has been reported to constitute a major challenge to about 1.5 billion people or 19% of the world population; whereas 70 million people globally exposed to flooding every year while over 800 million people are living in flood-prone areas. The 2022 destructive flooding in River Niger Basin Lokoja Nigeria has attracted attention of experts with a view to curtailing the future reoccurrence. Based on this rationale, this study aimed to determine the trend in the hydrometric dataset and to provide extensive time series analysis of the streamflow in the study area using Modified Thomas Fierring Model (MTFM). In order to achieve the objectives of the study, the dataset for 20 years was sourced from the NIWA (National Inland Waterway Authority) whereby the daily and monthly data was extensively analyzed and the (Thomas Fierring) T-F model the data for the “n” years was divided into 12 sections while the data of each month was re-aggressed to the previous month so that there were 12 linear regressions. Also, MTFM was used to predict the monthly flows from River Niger from 2000 to 2019 so as to compute 36 parameters (12) means (), standard deviations (), and Lag-1 autocorrelation coefficients (r1)). After the estimation of the parameters of the MTFM, the series of historical monthly flows for 20 years were generated. These series were compared with the recorded monthly flows of River Niger for the hydrological period of 20 years (2000-2019), with the use of basic statistical characteristics like mean, standard deviation, maximum, minimum, coefficient of variation, skewness and Kurtosis as shown in Table 1 and Figure 2. The findings revealed that monthly discharge time series of River Niger Basin from 2000 to 2019 are consistent with slightly variation in the trends after modified modified Thomas Fierring Model application; and the study further underscored the relevance of MTFM for analyzing streamflow of River Niger Basin Lokoja. Among others, the study recommended up-to-date hydrometric data of River Niger Basin for optimum control and management of streamflow in the study area; and concluded that up-to-date information in this direction will help future researcher to consolidate on the existing body of knowledge in the field.

Predicting River Discharge in the Niger River Basin: A Deep Learning Approach

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.

Remote sensing analysis of desert sensitive areas using MEDALUS model and GIS in the Niger River Basin

Environmental degradation is a dynamic issue that requires ongoing monitoring to ensure ecological repair and environmental management for sustainable development. This study employed remote sensing techniques to ascertain the desertification sensitivity areas in the Niger River Basin (NRB) using the MEDALUS Model. The indicators for the model were divided into three categories: vegetation quality,climate quality, and soil quality index. The net primary productivity, estimated by the Carnegie Ames Stanford Approach model was substituted in the vegetation quality index. Each quality index was computed by calculating the geometric mean of selected sub-indices, while the geometric mean of the three quality indicators was utilized to determine the Environmental sensitivity to desertification in the study area. A total of 26.10% of the study area had low soil quality, while 26.16% and 17.41% of the study area had low vegetation and climate indicators, respectively. The study revealed that about 36.56% of the study area is highly sensitive while 27.65% and 35.78% are moderately and less sensitive respectively, to desertification in the NRB. The desertification-sensitivity index map shows that the northern part of the study area is highly susceptible to desertification and is encroaching southwards. The findings reveal that climate variables are major influencers in the study area. Our research is of importance to the Niger Basin Authority, planners, and other government agencies in charge of protecting the environment, to ascertain the sensitive areas to desertification, and to help cushion the effect of land degradation in the NRB.

Food Security Status and Coping Strategies of Households in Inland Fisheries: Evidence from Fishermen from Niger River Basin

Inland fisheries play an important role in economic growth and food security in developing landlocked countries. In Mali, fishing from the Niger River contributes to national food security and nutrition but the food status of fishermen remains a research question to be explored. The objective of this study is to analyze the security status and coping strategies of fishermen households' in Pelengana municipality located along the Niger River in the Segou region. The adopted methodology is based on the food security index (FSI) which is a composite indicator based on Food consumption score (FCS), Economic vulnerability (EV), and Coping strategy index (CSI). The collection of data by survey concerned 204 households of fishermen in the municipality. The results of the FSI analysis indicate all fishermen's households are food secure. According to the FCS, EV, and CSI analysis, 1.3%, 6.9% and, 8.3% are food insecure. The households sell the fish and buy 98% of their food at the market. In conclusion, fishing allows fishermen to ensure their food security through the generated income for purchasing food at the market. The study encourages development partners and the government of Mali to invest in the development of the fish value chain to improve incomes and strengthen the food security of stakeholders, especially fishermen. For further research, an in-depth analysis of the impact of fish chain development on national food security is needed.

Remote sensing approach in evaluating anthropogenic impacts on the spatiotemporal changes in net primary productivity of the Niger river basin, from 2000 to 2020

Deterioration of the environment can be examined by utilizing a statistical evaluation of the effects of anthropogenic activities (beneficial or detrimental) on net primary productivity. The Niger River Basin's net primary productivity is significant both theoretically and practically for the management of the natural environment. It is important for her member countries to understand vegetation dynamics, maintain carbon balance, and ensure food security in the region. The research applied remote sensing to determine the relative impact of human activities on the net primary productivity of the Niger River Basin from 2000 to 2020. The study simulated the actual and potential net primary productivity using the Carnegie Ames Stanford Approach and Thornthwaite's Memorial Model respectively, while the result of the simulations was used to calculate human-influenced net primary productivity. The slope of the three simulations was calculated and merged in several scenarios using ArcGIS 10.8 to determine the impact of human activities on net primary productivity of the study area. The negative impacts of human activities were recorded in 89.88 % of the investigated area, while 10.12 % of the NRB had signs of positive impacts. Amongst the biomes, urban areas and bare land experienced the largest negative impacts (97.2 % and 99.8 %, respectively). The study advised the effectiveness of ecological restoration programs, through sound scientific and technical methods, such as those used in rural development, nomadic herding, environmental protection, and natural resource management policies.

Building Tools for further Investigating Acid Mining Production: Intercomparison of Four Hydrological Model Versions through a Scoring Technique on the Niger River Basin, in west Africa

We modify a framework to model time series of discharges, on watersheds of the Niger River and its tributaries, over 1901- 2020. This framework is built from a French hydrological model – Genie Rural with 2 parameters at Monthly time step – GR2M. The first parameter, X1, concerns the input variables. This parameter is applied to the rainfall and the evapotranspiration data; its reciprocal, 1/X1, is applied to the Soil’s Water Holding Capacity data (assimilated to reservoir height). The second parameter, X2, is applied to the time series of discharges, which is the output variable in modelling. Modifications lead to a new model version called SimulHyd, which stands for Simulation of Hydrological systems. A weighting rule on grids is inserted into the framework to create a gridded variant of semi-distributed modelling from a lumped model. Following a World Meteorological Organization’s goal, we develop a scoring technique for intercomparisons of model versions on both one single and several catchments. Over the 16 watersheds, a three-model intercomparison shows the preponderance of SimulHyd semi distributed (with 117.83 out of 192 total scoring-points, equivalent to 61.37%) over both GR2M nondistributed (with 61.33 scoring-points, or 31.94%) and GR2M semi-distributed (with 12.83 scoring-points, or 6.68%).

Public preference of flood-resilient housing technologies in Nigeria: a case study of Kogi State

Purpose The purpose of this paper is to explore flood-prone area residents' preferences of flood-resilient housing technologies (HTs), to understand the factors influencing their choices. Flood-resilient HTs can reduce damage and disruption at a household level, particularly in areas where large-scale community schemes are not available or feasible. People’s perception of floods and their preferences of flood-resilient HTs are among many very important factors influencing the adoption of these technologies. Therefore, these perceptions and preferences must be well understood before implementation of these technologies can occur. However, studies on these two important factors are lacking in literature, particularly in the sub-Saharan African context. Design/methodology/approach Nigerian residents’ preferences of flood-resilient HTs were explored by focusing on five frequently flooded areas around the Niger and Benue river basins in Kogi State, Nigeria. Thirty-eight chat, video and voice call interviews were conducted with participants across five case study areas: Lokoja, Idah, Bassa, Ajaokuta and Koton Karifi. The interviews, informed through an illustrated brochure, covered residents’ experiences and perceptions of floods. This was done to gain an understanding of the factors influencing the choice of flood-resilient HTs adopted and those preferred. Findings This study confirms that residents in these five focus areas show similar characteristics to other floodplain residents as encapsulated in protection motivation theory. The flood-resilient HTs discussed in this study include flood-avoidance, flood-recoverability and flood-resistance strategies, as well as neighbourhood-scale approaches. Flood-resistance and flood-recoverability strategies rated highly in terms of suitability and envisaged efficiency in mitigating flooding in Kogi State. Although the measures were mostly agreed to be potentially effective and successful on a household scale, there were concerns as to flood mitigation on a neighbourhood scale. Research limitations/implications Pre-existing flood-resilient HTs were not extensively discussed in the literature review but were included to have a sense of the participants’ mitigation behaviour, as well as their potential to adopt (or not) new measures after adopting previous ones. Originality/value The results provide supporting evidence of the factors influencing the choice of and/or intention to adopt flood-resilient HTs, highlighted in literature. Results also contribute to literature by providing further insight into flood-resilient measures already adopted by residents, as well as their preferred HTs from the options presented. The implications of these findings and methodological considerations in this research are fully discussed in this paper.

Assessment of Stakeholder Involvement and Borehole Water Projects Delivery in Kogi West Senatorial District, Nigeria

There is huge challenges in the supply of clean water for household consumption in many countries, in particular, Nigeria. Kogi West Senatorial District (KWSD) has witnessed more borehole projects in Nigeria but the challenge of clean water still persists. This has necessitated more research into the field of water resources to combat such challenges in line with the sustainable development goals (SDGs). This study assessed the effects of stakeholders’ involvement in KWSD, Nigeria, with a view to improving the delivery of borehole water projects in the study area. Data were collected through a structured questionnaire from 267 stakeholders comprising Lower Niger River Basin Development Authority (LNRBDA) staff, community leaders and community members that were selected using simple random sampling technique. The study objective was assessed with inferential statistics (Partial Least Square in Structural Equation Modelling). The results disclose the direct path coefficients for Initiation stage (bIS), Planning stage (bPS), Execution stage (“bES”), Monitoring and closure stage (bMS), Post construction stage (bPCS), Budget (cBG), Time Delivery (cTD) and Stakeholder’s Satisfaction (cSS). The results illustrated positives and significant relationship with bES -&gt; cBG (β = 0.422, t = 5.708), bES -&gt; cSS (β = 0.495, t = 6.366), bES -&gt; cTD (β = 0.493, t = 7.422), bMS -&gt; cBG (β = 0.164, t = 2.643), bPCS -&gt; cTD (β = 0.257, t = 5.7084.440), and negative significant relationship with bMS -&gt; cTD (β = -0.184, t = 2.547) and bPS -&gt; cSS (β = - 0.182, t = 2.586). The study concludes that stakeholders’ involvement is a strong predictor of viable Borehole water projects delivery in the study area.

Environmental and spatial determinants of fish community structure in an Afro‐tropical river ecosystem

AbstractWe investigated the relative influence of local environmental and spatial factors in structuring the community composition of fish at 15 sampling sites along the longitudinal gradient of the Lower Niger River Basin (LNRB) in dry and rainy seasons using distance‐based redundancy analysis and variation partitioning analysis. We collected a total of 3807 fish specimens representing 42 species. Our result indicated that the fish community composition differed between the upper and lower regions of the river. The communities in the upper region is influenced by high‐nutrient concentrations, while downstream sites were characterized by high concentrations of suspended solids. Variation partitioning revealed higher contributions of spatial than environmental predictors on fish community composition, with a higher total predicted variance in dry season. The variations in the community composition between upper and lower region may be attributable to the differences in the nature of anthropogenic activities within the regions, which influenced the local conditions differently. Differences in flow dynamics between upper and lower regions as attributable to black and white floods in the LNRB modify the connectivity between sites. Dispersal among sites may be more limited downstream than in the upper region, particularly in the dry season, because damming in the upper region also interrupts the natural flood regime such that there are low water levels in the lower region, which spatially isolate fish communities at certain sampling sites. The relatively higher total predicted variance during dry season may be attributable to the temporal differences in abiotic conditions between sites, which may have influenced site level community composition and abundance differently.

Assessing impacts of climate variability and land use/land cover change on the water balance components in the Sahel using Earth observations and hydrological modelling

Study regionSenegal river (SRB), Niger river (NRB), and Lake Chad basins (LCB). Study focusWe investigated the impacts of land use/land cover change (LULC) and climate variability on the water balance components from 1990 to 2020. We applied the Soil and Water Assessment Tool (SWAT) coupled with remote sensing retrievals of actual evapotranspiration (ETa) and surface soil moisture (SSM). To separate the impacts of the two aforementioned factors, two numerical experiments were designed: (i) climate variability effects by applying frozen LULC while changing the climate; (ii) LULC change impacts by applying frozen climate while changing LULC. New hydrological insights for the regionOverall, at the basin level, the results indicated that climate variability had the dominant role in increasing groundwater recharge, surface runoff, groundwater return flow and lateral flow in LCB and SRB. These increases triggered the recovery of lake area and higher water table in LCB and increased in SRB streamflow, while water scarcity increased in NRB. In contrast, the separate effect of LULC change, specifically natural vegetation expansion, increased actual ET and decreased the surface runoff, which could be a reason for lake area depletion in LCB and decreasing SRB and NRB streamflow. At the sub-basin level, LULC change, i.e. a gain in cropland and urban areas at the expense of forests in some sub-basins in NRB, led to a local increase in surface runoff. This implies a better redistribution of water in downstream and compensates the deficit in surface runoff caused by natural vegetation expansion in some other catchments. These changes, simultaneously with high intensity and long-duration precipitation, may increase the likelihood of inundation in some small catchments in the Niger river basin. These outcomes give useful hydrological insights into water and land management by emphasizing the crucial role of water recycling.

Modelling Distributions of Asian and African Rice Based on MaxEnt

Rice landraces, including Asian rice (Oryza sativa L.) and African rice (Oryza glaberrima Steud.), provide important genetic resources for rice breeding to address challenges related to food security. Due to climate change and farm destruction, rice landraces require urgent conservation action. Recognition of the geographical distributions of rice landraces will promote further collecting efforts. Here we modelled the potential distributions of eight rice landrace subgroups using 8351 occurrence records combined with environmental predictors with Maximum Entropy (MaxEnt) algorithm. The results showed they were predicted in eight sub-regions, including the Indus, Ganges, Meghna, Mekong, Yangtze, Pearl, Niger, and Senegal river basins. We then further revealed the changes in suitable areas of rice landraces under future climate change. Suitable areas showed an upward trend in most of study areas, while sub-regions of North and Central China and West Coast of West Africa displayed an unsuitable trend indicating rice landraces are more likely to disappear from fields in these areas. The above changes were mainly determined by changing global temperature and precipitation. Those increasingly unsuitable areas should receive high priority in further collections. Overall, these results provide valuable references for further collecting efforts of rice landraces, while shedding light on global biodiversity conservation.

Проект «Скопа в России»: основные результаты работы в 2019–2023 годах

Проект «Скопа в России»: основные результаты работы в 2019–2023 годах