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Journal articles on the topic 'Niger river basin'

Author: Grafiati

Published: 4 June 2021

Last updated: 7 February 2022

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1

Okoli, Chucks. "The Hydrometeorology of Niger River Basin." Advanced Materials Research 824 (September 2013): 613–29. http://dx.doi.org/10.4028/www.scientific.net/amr.824.613.

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This paper examines the mean annual cycle of rainfall and general circulation features over the Niger River Basin consisting of mainly West Africa and Central Africa regions. Rainfall is examined using a 1400-station archive compiled by earlier workers. Other circulation features are examined using the NCEPNCAR reanalysis dataset. Important features of the reanalysis zonal wind field are shown to compare well with the seasonal evolution described by the radiosonde observations. In addition to the well-known African easterly jet (AEJ) of the Northern Hemisphere, the seasonal evolution of its Southern Hemisphere counterpart is also described. Thermal wind calculations show that although the southern jet is weaker, its existence is also due to a local reversal of the surface temperature gradient. In the upper troposphere, a strong semiannual cycle is shown in the 200-mb easterlies and a feature like the tropical easterly jet (TEJ) is evident south of the equator in January and February. The paper describes the movement of the rainbelt between central and West Africa. An asymmetry in the northward and southward migration of the rainbelt is evident. The paper discusses the influence that the jets may have on rainfall and possible feedback effects of rainfall on the jets. Evidence suggests that the midtropospheric jets influence the development of the rainy season, but also that the rainfall affects the surface temperature gradient and in turn the jets. In the Northern Hemisphere, east of 200E, the axis of the TEJ is located so that it may promote convection by increasing upper-level divergence. However, west of 100E and in the Southern Hemisphere, the location of the TEJ is consistent with the suggestion that it is the equatorward outflow of convection that produces the TEJ. The paper notes that rainfall and river flow is largely influenced by groundwater base flow, and a return to sustained river flow requires replenishment of the aquifers, which is possible only with cumulative raining years. The paper confirms that there is correlation between the decrease in rainfall and low river flows.

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2

Sorí, Rogert, Raquel Nieto, Anita Drumond, and Luis Gimeno. "The Niger River Basin Moisture Sources: A Lagrangian Analysis." Atmosphere 8, no. 12 (February 14, 2017): 38. http://dx.doi.org/10.3390/atmos8020038.

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3

Ogilvie, Andrew, Gil Mahé, John Ward, Georges Serpantié, Jacques Lemoalle, Pierre Morand, Bruno Barbier, et al. "Water, agriculture and poverty in the Niger River basin." Water International 35, no. 5 (November 4, 2010): 594–622. http://dx.doi.org/10.1080/02508060.2010.515545.

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4

Andersson, Jafet C. M., Abdou Ali, Berit Arheimer, David Gustafsson, and Bernard Minoungou. "Providing peak river flow statistics and forecasting in the Niger River basin." Physics and Chemistry of the Earth, Parts A/B/C 100 (August 2017): 3–12. http://dx.doi.org/10.1016/j.pce.2017.02.010.

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5

Akana, Tombra, and Olubunmi Adeigbe. "Channel characteristics and planform dynamics of the lower Niger River, Niger Delta Basin (1985–2015)." Geology, Geophysics and Environment 45, no. 4 (January 25, 2020): 291. http://dx.doi.org/10.7494/geol.2019.45.4.291.

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This study used repeat satellite imagery and Geographic Information System analysis to assess the plan-form dynamics along the length of the lower Niger River Valley from Onitsha city to the coast between 1985 and 2015. The aim is to understand the altered dynamics and its plausible causes in this data-poor region. Analyses revealed that the Niger River has undergone change corresponding to enhanced instability in terms of an increased rate of erosion. In the study area, a change was observed from 3.7% of deposition in the first 10 years (1985–1995) to 3.9% of erosion in the next 10 years (1995–2005) and 4.7% of erosion in the last 10 years (2005–2015). Total erosion over the 30-year period (1985–2015) in the delta was calculated on 4.8%. The river channel has migrated toward the east in the upper and lower reaches while the mid-section of the channel is migrating towards the west. The east river bank is observed to be more unstable compared to west bank line through the study period. The maximum shifts identified were 3.35 km of deposition in 10 years (1985–1995), 3.31 km of erosion in the next 10 years (1995–2005), and another substantial erosional shift of 3.35 km in the next 10 years (2005–2015). Avulsion rates gradually moved from −42.1 m ∙ year−1 (1985–2005, segment F) to 100.2 m ∙ year−1 (1985–1995, segment D), large deposition in the first 10 years. Total avulsion rates of the delta in the last 30 years (1985–2015) has pointed on erosion (−2.2 m ∙ year−1). The altered dynamics observed would likely threaten the future of the frag-ile lower river system environment and raise concerns for operators with infrastructure within the Niger Delta.

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6

Aich, Valentin, Bakary Koné, Fred Hattermann, and Eva Paton. "Time Series Analysis of Floods across the Niger River Basin." Water 8, no. 4 (April 21, 2016): 165. http://dx.doi.org/10.3390/w8040165.

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7

Landis, Steven T., Babak Rezaeedaryakenari, Yifan Zhang, Cameron G. Thies, and Ross Maciejewski. "Fording differences? Conditions mitigating water insecurity in the Niger River Basin." Political Geography 56 (January 2017): 77–90. http://dx.doi.org/10.1016/j.polgeo.2016.10.002.

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8

Werth, S., D. White, and D. W. Bliss. "GRACE Detected Rise of Groundwater in the Sahelian Niger River Basin." Journal of Geophysical Research: Solid Earth 122, no. 12 (December 2017): 10,459–10,477. http://dx.doi.org/10.1002/2017jb014845.

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9

Sorí, Rogert, Raquel Nieto, Anita Drumond, Milica Stojanovic, and Luis Gimeno. "On the Connection between Atmospheric Moisture Transport and Dry Conditions in Rainfall Climatological Zones of the Niger River Basin." Water 11, no. 3 (March 26, 2019): 622. http://dx.doi.org/10.3390/w11030622.

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The hydroclimatology of the Niger River basin, located in West Africa, is very complex. It has been widely studied because of its importance to the socioeconomic activities of the countries that share its natural resources. In this study, to better understand the causes and mechanisms that modulate the rainfall over the Niger River basin, we identified the most relevant moisture sources for precipitation within the basin. The Lagrangian model FLEXPART was utilised to track backward trajectories of air parcels initially losing humidity over climatological rainfall zones of the basin. Along 10-day backward trajectories, we computed the budget of the difference between evaporation and precipitation (E − P) from 1000 to 0.1 hPa, permitting the identification of those regions where moisture uptake ((E − P) > 0) prevail. The study was conducted for the period 1980–2017. Monthly maps of ((E − P) > 0 were developed to illustrate the regions from where moisture is transported, contributing to precipitation in the Niger River basin. The spatial variability of the sources matches the precipitation variability over the basin restricted to surrounding areas of the Niger River basin during months with low average precipitation and widely spreading over the continent and the Atlantic Ocean in months with high average precipitation. During climatological dry months (e.g., December, January and February) the continental sources of West and Northeast Africa and the climatological rainfall zones themselves provide most of the moisture for precipitation. However, during the rainy season, the moisture supplies from oceanic sources increase, becoming greater than the contribution from land-based sources during August (the rainiest month). Dry conditions were identified for each climatological rainfall zone using the Standardised Precipitation Index. Similar to many previous studies, we found that the 1980s were highlighted by dry conditions. Local recycling and particularly moisture uptake from the tropical South Atlantic Ocean seem to be highly related to dry and wet conditions in the basin. A reduction on the moisture uptake from surrounding continental sources and the tropical South Atlantic Ocean is almost persistent during extremely dry conditions. Ascending movements are restricted to the lower troposphere during extremely dry conditions and oscillate latitudinally as well as precipitation.

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10

Eme, L. C., J. A. Ulasi, A. I. Alade Tunde, and A. C. Odunze. "Hydrokinetic turbines for power generation in Nigerian river basins." Water Practice and Technology 14, no. 1 (January 21, 2019): 71–80. http://dx.doi.org/10.2166/wpt.2019.001.

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Abstract This work presents a design for Hydrokinetic Renewable Energy (HRE), for off grid power generation for remote riverine regions in developing nations. The uniqueness of this technique for power generation using streams and other marine currents to generate electric energy is detailed. The problem of the impact of greenhouse gas emissions on the environment, rapid increase in human population, industries, modernization and our lifestyle put immense pressure on most power generation plants and infrastructures. Thus, global warming and carbon footprints of using fossil fuels to generate energy has driven the interest for energy generation from renewable sources. The Upper River Benue and Lower River Niger coastal basins, as well as the River Niger Basin on the Lower Niger sub-basin area of southeastern Nigeria was selected as a case study for the design of the hydrokinetic power generation technology. The results show that for a hydrokinetic turbine the level of power output is directly proportional to the flow velocity. Therefore the cost of its installation is reduced drastically from about $7,900 per installed kW to about $2,500 per kW, is easily assessable, less technical and a familiar motor technology for most of these communities. It is also a predictable form of energy in comparison to other emerging renewable energy fields like wind, solar and wave. Also this form of renewable energy is less harmful to the environment, has a lower noise emission and produces no greenhouse gases or any solid waste. HRE will bring energy security that is essential for the riverine dweller and curb rural urban migration and both improves the rural communities' standard of living and enhances their productivity.

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11

Massazza, Giovanni, Maurizio Bacci, Luc Descroix, Mohamed Housseini Ibrahim, Edoardo Fiorillo, Gaptia Lawan Katiellou, Geremy Panthou, et al. "Recent Changes in Hydroclimatic Patterns over Medium Niger River Basins at the Origin of the 2020 Flood in Niamey (Niger)." Water 13, no. 12 (June 14, 2021): 1659. http://dx.doi.org/10.3390/w13121659.

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Niamey, the capital of Niger, is particularly prone to floods, since it is on the banks of the Niger River, which in its middle basin has two flood peaks: one in summer (the red flood) and one in winter (the black flood). In 2020, the Niger River in Niamey reached its all-time highest levels following an abundant rainy season. On the other hand, the floods in Niamey have been particularly frequent in the last decade, a symptom of a change in hydroclimatic behaviour already observed since the end of the great droughts of the 1970s and 1980s and which is identified with the name of Sahelian Paradox. This study, starting from the analysis of the 2020 flood and from the update of the rating curve of the Niamey hydrometric station, analyses the rainfall–runoff relationship on the Sahelian basins of the Medium Niger River Basin (MNRB) that are at the origin of the local flood. The comparative analysis of runoffs, annual maximum flows (AMAX) and runoff coefficients with various rainfall indices calculated on gridded datasets allowed to hydroclimatically characterise the last decade as a different period from the wet one before the drought, the dry one and the post-drought one. Compared to the last one, the current period is characterised by a sustained increase in hydrological indicators (AMAX +27%) consistent with the increase in both the accumulation of precipitation (+11%) and the number (+51%) and magnitude (+54%) of extreme events in the MNRB. Furthermore, a greater concentration of rainfall and extremes (+78%) in August contributes to reinforcing the red flood’s positive anomalies (+2.23 st.dev in 2020). The study indicates that under these conditions the frequency of extreme hydrological events in Niamey will tend to increase further also because of the concurrence of drivers such as river-bed silting and levee effects. Consequently, the study concludes with the need for a comprehensive flood-risk assessment on the Niamey city that considers both recent hydroclimatic trends and urbanisation dynamics in flood zones hence defining the most appropriate risk-reduction strategies.

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12

Bâ, Khalidou, Luis Balcázar, Vitali Diaz, Febe Ortiz, Miguel Gómez-Albores, and Carlos Díaz-Delgado. "Hydrological Evaluation of PERSIANN-CDR Rainfall over Upper Senegal River and Bani River Basins." Remote Sensing 10, no. 12 (November 27, 2018): 1884. http://dx.doi.org/10.3390/rs10121884.

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This study highlights the advantage of satellite-derived rainfall products for hydrological modeling in regions of insufficient ground observations such as West African basins. Rainfall is the main input for hydrological models; however, gauge data are scarce or difficult to obtain. Fortunately, several precipitation products are available. In this study, Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks–Climate Data Record (PERSIANN-CDR) was analyzed. Daily discharges of three rivers of the Upper Senegal basin and one of the Upper Niger basin, as well as water levels of Manantali reservoir were simulated using PERSIANN-CDR as input to the CEQUEAU model. First, CEQUEAU was calibrated and validated using raw PERSIANN-CDR, and second, rainfalls were bias-corrected and the model was recalibrated. In both cases, ERA-Interim temperatures were used. Model performance was evaluated using Nash–Sutcliffe efficiency (NSE), mean percent bias (MPBIAS), and coefficient of determination (R2). With raw PERSIANN-CDR, most years show good performance with values of NSE > 0.8, R2 > 0.90, and MPBIAS < 10%. However, bias-corrected PERSIANN-CDR did not improve the simulations. The findings of this study can be used to improve the design of dam projects such as the ongoing dam constructions on the three rivers of the Upper Senegal Basin.

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13

Ologhadien, Itolima. "Developments in river bank protection schemes in the lower Niger delta basin." MOJ Civil Engineering 5, no. 2 (2019): 58–67. http://dx.doi.org/10.15406/mojce.2019.05.00150.

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14

Babatolu, Joseph Sunday, and Rufus Temidayo Akinnubi. "Surface Temperature Anomalies in the River Niger Basin Development Authority Areas, Nigeria." Atmospheric and Climate Sciences 03, no. 04 (2013): 532–37. http://dx.doi.org/10.4236/acs.2013.34056.

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15

Akumaga, Uvirkaa, and Aondover Tarhule. "Projected Changes in Intra-Season Rainfall Characteristics in the Niger River Basin, West Africa." Atmosphere 9, no. 12 (December 14, 2018): 497. http://dx.doi.org/10.3390/atmos9120497.

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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.

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16

Pedinotti, V., A. Boone, B. Decharme, J. F. Crétaux, N. Mognard, G. Panthou, and F. Papa. "Characterization of the hydrological functioning of the Niger basin using the ISBA-TRIP model." Hydrology and Earth System Sciences Discussions 8, no. 5 (October 14, 2011): 9173–227. http://dx.doi.org/10.5194/hessd-8-9173-2011.

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Abstract. During the 70s and 80s, West Africa has faced extreme climate variations with extended extreme drought conditions. Of particular importance is the Niger basin, since it traverses a large part of the Sahel and is thus a critical source of water in this semi arid region. However, the understanding of the hydrological processes over this basin is currently limited by the lack of spatially distributed surface water and discharge measurements. The purpose of this study is to use the ISBA-TRIP continental hydrologic system to explore key processes related to the hydrological cycle of the Niger Basin. The scheme accounts explicitly for the surface river routing, for the floodplains dynamic, and for the water storage using a deep aquifer reservoir. In the current study, simulations are done at a 0.5 by 0.5° spatial resolution over the 2002–2007 period using the atmospheric forcing provided by the AMMA Land surface Model Intercomparison Project (ALMIP). The model is intensively compared to in situ discharge measurements as well as satellite derived flood extent, total continental water storage changes and river height changes. The flooding scheme leads to a non-negligible increase of evaporation over large flooded areas, which decrease the Niger river flow by 15% to 50%, according to the observed station and the rainfall dataset used as forcing. This contributes to improve the simulation of the river discharges confirming for the need to incorporate flood representations into Land Surface Model. The model provides a good estimation of the surface water dynamics and accurately simulates the endorheic property of the Northern part of the basin. Moreover, the deep aquifer reservoir improves Niger low flows and the recession law during the dry season. This study also gives a basic estimation of aquifer recharge and of the total terrestrial water budget. The comparison with 3 satellite products from the Gravity Recovery and Climated Experiment (GRACE) is really optimistic and show a non negligible contribution of the deeper soil layers to the total storage (26% for groundwater and aquifer). Finally, sensitivity tests have shown that a good parameterization of routing models is required to optimize simulation errors. Indeed, the modification of some key parameters has non-negligible impacts on the model dynamics which gives perspectives for improving the model input parameters using future developments in remote sensing technologies such as the joint CNES-NASA satellite project SWOT (Surface Water Ocean Topography), which will provide water heights and extent at land surface with an unprecedented 50–100 m resolution and precision.

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17

Pandey, R., and G. Amarnath. "The potential of satellite radar altimetry in flood forecasting: concept and implementation for the Niger-Benue river basin." Proceedings of the International Association of Hydrological Sciences 370 (June 11, 2015): 223–27. http://dx.doi.org/10.5194/piahs-370-223-2015.

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Abstract. Flood forecasting in the downstream part of any hydrological basin is extremely difficult due to the lack of basin-wide hydrological information in near real-time and the absence of a data-sharing treaty among the transboundary nations. The accuracy of forecasts emerging from a hydrological model could be compromised without prior knowledge of the day-to-day flow regulation at different locations upstream of the Niger and Benue rivers. Only satellite altimeter monitoring allows us to identify the actual river levels upstream that reflect the human intervention at that location. This is critical for making accurate downstream forecasts. This present study aims to demonstrate the capability of altimeter-based flood forecasting along the Niger-Benue River in Nigeria. The study includes the comparison of decadal (at every 10 days from Jason-2) or monthly (at every 35 days from Envisat/AltiKa) observations from 2002 to 2014, with historical in situ measurements from 1990 to 2012. The water level obtained from these sources shows a good correlation (0.7–0.9). After validation of hydrological parameters obtained from two sources, a quantitative relation (rating curve) of upstream water level and downstream discharge is derived. This relation is then adopted for calculation of discharge at observation points, which is used to propagate the flow downstream at a desired location using a hydraulic river model. Results from this study from Jason-2 shows a promising correlation (R2 ≥ 90% with a Nash-Sutcliffe coefficient of more than 0.70) with 5~days ahead of downstream flow prediction over the Benue stream.

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18

B, Alhou, Issiaka Boukari, and Darchambeau F. "Apports En Carbone Et Azote Dans Le Fleuve Niger À Tondibia (Niamey) : Résultats De Deux (2) Ans D’observations." European Scientific Journal, ESJ 12, no. 21 (July 29, 2016): 167. http://dx.doi.org/10.19044/esj.2016.v12n21p167.

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The Niger River is the third more important river in Africa and drains a surface of about 2,120,000 km². It includes six hydrographic regions representing West African ecosystems. Despite the importance of this river at the regional and continental scale, little information has been collected on its biogeochemical characteristics and particularly on its role in the transportation and the transformation of matter (carbon, nitrogen and phosphorus). This study present the results of two years investigation, April 2011 to March 2013 in the middle Niger, upstream Niamey (Niger) city [2.01° E, 13.57° N], according to a bi-weekly observation frequency. The variables measured are temperature, conductivity, dissolved oxygen, pH, suspended matter, dissolved inorganic carbon (C) and nitrogen (N) and particulars organics C and N as well as isotopic composition of these elements. Daily discharges of the river come from hydrologic station measurement of the Niger authority Basin (NBA) at Niamey city. Hydrologic situation was strongly contrasted between the 2 years of survey. The mean discharge of the first year was only 673 m3 s-1 (one of the weakest discharge recorded on the river Niger at Niamey since 1940), while the mean discharge of the second year was 1,096 m3 s-1. Our results show that suspended matter, particular organic carbon, dissolved organic carbon and dissolved inorganic carbon are transported mainly during the local flood, induced by precipitations in July and August. The second flood (Guinean flood) which occurred, during November to January, is characterized by low temperatures and clean waters.

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19

Vetter, T., S. Huang, V. Aich, T. Yang, X. Wang, V. Krysanova, and F. Hattermann. "Multi-model climate impact assessment and intercomparison for three large-scale river basins on three continents." Earth System Dynamics Discussions 5, no. 2 (July 4, 2014): 849–900. http://dx.doi.org/10.5194/esdd-5-849-2014.

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Abstract. Climate change impacts on hydrological processes should be simulated for river basins using validated models and multiple climate scenarios in order to provide reliable results for stakeholders. In the last 10–15 years climate impact assessment was performed for many river basins worldwide using different climate scenarios and models. Nevertheless, the results are hardly comparable and do not allow to create a full picture of impacts and uncertainties. Therefore, a systematic intercomparison of impacts is suggested, which should be done for representative regions using state-of-the-art models. Our study is intended as a step in this direction. The impact assessment presented here was performed for three river basins on three continents: Rhine in Europe, Upper Niger in Africa and Upper Yellow in Asia. For that, climate scenarios from five GCMs and three hydrological models: HBV, SWIM and VIC, were used. Four "Representative Concentration Pathways" (RCPs) covering a range of emissions and land-use change projections were included. The objectives were to analyze and compare climate impacts on future trends considering three runoff quantiles: Q90, Q50 and Q10 and on seasonal water discharge, and to evaluate uncertainties from different sources. The results allow drawing some robust conclusions, but uncertainties are large and shared differently between sources in the studied basins. The robust results in terms of trend direction and slope and changes in seasonal dynamics could be found for the Rhine basin regardless which hydrological model or forcing GCM is used. For the Niger River scenarios from climate models are the largest uncertainty source, providing large discrepancies in precipitation, and therefore clear projections are difficult to do. For the Upper Yellow basin, both the hydrological models and climate models contribute to uncertainty in the impacts, though an increase in high flows in future is a robust outcome assured by all three hydrological models.

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20

Andersson, Jafet C. M., Berit Arheimer, Farid Traoré, David Gustafsson, and Abdou Ali. "Process refinements improve a hydrological model concept applied to the Niger River basin." Hydrological Processes 31, no. 25 (November 16, 2017): 4540–54. http://dx.doi.org/10.1002/hyp.11376.

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21

Munier, S., A. Polebistki, C. Brown, G. Belaud, and D. P. Lettenmaier. "SWOT data assimilation for operational reservoir management on the upper Niger River Basin." Water Resources Research 51, no. 1 (January 2015): 554–75. http://dx.doi.org/10.1002/2014wr016157.

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22

Oguntunde, Philip G., and Babatunde J. Abiodun. "The impact of climate change on the Niger River Basin hydroclimatology, West Africa." Climate Dynamics 40, no. 1-2 (August 28, 2012): 81–94. http://dx.doi.org/10.1007/s00382-012-1498-6.

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23

Béné, Christophe, Louisa Evans, David Mills, Solomon Ovie, Aminu Raji, Ahmadu Tafida, Amaga Kodio, et al. "Testing resilience thinking in a poverty context: Experience from the Niger River basin." Global Environmental Change 21, no. 4 (October 2011): 1173–84. http://dx.doi.org/10.1016/j.gloenvcha.2011.07.002.

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24

Ghile, Y. B., M. Ü. Taner, C. Brown, J. G. Grijsen, and Amal Talbi. "Bottom-up climate risk assessment of infrastructure investment in the Niger River Basin." Climatic Change 122, no. 1-2 (November 17, 2013): 97–110. http://dx.doi.org/10.1007/s10584-013-1008-9.

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25

Picouet, Cécile, Benoît Hingray, and Jean Claude Olivry. "Modelling the suspended sediment dynamics of a large tropical river: the Upper Niger river basin at Banankoro." Hydrological Processes 23, no. 22 (October 30, 2009): 3193–200. http://dx.doi.org/10.1002/hyp.7398.

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26

Salami, Adebayo Wahab, Oseni Taiwo Amoo, Joshiah Adetayo Adeyemo, Abdulrasaq Apalando Mohammed, and Adeniyi Ganiyu Adeogun. "Morphometrical Analysis and Peak Runoff Estimation for the Sub-Lower Niger River Basin, Nigeria." Slovak Journal of Civil Engineering 24, no. 1 (March 1, 2016): 6–16. http://dx.doi.org/10.1515/sjce-2016-0002.

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AbstractThis study utilized Spatial Information Technology (SIT) such as Remote Sensing (RS), a Geographical Information System (GIS), the Global Positioning System (GPS) and a high-resolution Digital Elevation Model (DEM) for a morphometrical analysis of five sub-basins within the Lower Niger River Basin, Nigeria. Morpho-metrical parameters, such as the total relief, relative relief, relief ratio, ruggedness number, texture ratio, elongation ratio, circularity ratio, form factor ratio, drainage density, stream frequency, sinuosity factor and bifurcation ratio, have been computed and analyzed. The study revealed that the contribution of the morphometric parameters to flooding suggest catchment No. 1 has the least concentration time and the highest runoff depth. Catchment No. 4 has the highest circularity ratio (0.35) as the most hazardous site where floods could reach a great volume over a small area.

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Scarcelli, Nora, Philippe Cubry, Roland Akakpo, Anne-Céline Thuillet, Jude Obidiegwu, Mohamed N. Baco, Emmanuel Otoo, et al. "Yam genomics supports West Africa as a major cradle of crop domestication." Science Advances 5, no. 5 (May 2019): eaaw1947. http://dx.doi.org/10.1126/sciadv.aaw1947.

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While there has been progress in our understanding of the origin and history of agriculture in sub-Saharan Africa, a unified perspective is still lacking on where and how major crops were domesticated in the region. Here, we investigated the domestication of African yam (Dioscorea rotundata), a key crop in early African agriculture. Using whole-genome resequencing and statistical models, we show that cultivated yam was domesticated from a forest species. We infer that the expansion of African yam agriculture started in the Niger River basin. This result, alongside with the origins of African rice and pearl millet, supports the hypothesis that the vicinity of the Niger River was a major cradle of African agriculture.

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Vetter, T., S. Huang, V. Aich, T. Yang, X. Wang, V. Krysanova, and F. Hattermann. "Multi-model climate impact assessment and intercomparison for three large-scale river basins on three continents." Earth System Dynamics 6, no. 1 (January 22, 2015): 17–43. http://dx.doi.org/10.5194/esd-6-17-2015.

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Abstract. Climate change impacts on hydrological processes should be simulated for river basins using validated models and multiple climate scenarios in order to provide reliable results for stakeholders. In the last 10–15 years, climate impact assessment has been performed for many river basins worldwide using different climate scenarios and models. However, their results are hardly comparable, and do not allow one to create a full picture of impacts and uncertainties. Therefore, a systematic intercomparison of impacts is suggested, which should be done for representative regions using state-of-the-art models. Only a few such studies have been available until now with the global-scale hydrological models, and our study is intended as a step in this direction by applying the regional-scale models. The impact assessment presented here was performed for three river basins on three continents: the Rhine in Europe, the Upper Niger in Africa and the Upper Yellow in Asia. For that, climate scenarios from five general circulation models (GCMs) and three hydrological models, HBV, SWIM and VIC, were used. Four representative concentration pathways (RCPs) covering a range of emissions and land-use change projections were included. The objectives were to analyze and compare climate impacts on future river discharge and to evaluate uncertainties from different sources. The results allow one to draw some robust conclusions, but uncertainties are large and shared differently between sources in the studied basins. Robust results in terms of trend direction and slope and changes in seasonal dynamics could be found for the Rhine basin regardless of which hydrological model or forcing GCM is used. For the Niger River, scenarios from climate models are the largest uncertainty source, providing large discrepancies in precipitation, and therefore clear projections are difficult to do. For the Upper Yellow basin, both the hydrological models and climate models contribute to uncertainty in the impacts, though an increase in high flows in the future is a robust outcome ensured by all three hydrological models.

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Modu, B., and B. Herbert. "Spatial analysis from remotely sensed observations of Congo basin of East African high Land to drain water using gravity for sustainable management of low laying Chad basin of Central Africa." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XL-1 (November 7, 2014): 279–86. http://dx.doi.org/10.5194/isprsarchives-xl-1-279-2014.

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The Chad basin which covers an area of about 2.4 million kilometer square is one of the largest drainage basins in Africa in the centre of Lake Chad .This basin was formed as a result of rifting and drifting episode, as such it has no outlet to the oceans or seas. It contains large area of desert from the north to the west. The basin covers in part seven countries such as Chad, Nigeria, Central African Republic, Cameroun, Niger, Sudan and Algeria. It is named Chad basin because 43.9% falls in Chad republic. Since its formation, the basin continues to experienced water shortage due to the activities of Dams combination, increase in irrigations and general reduction in rainfall. Chad basin needs an external water source for it to be function at sustainable level, hence needs for exploitation of higher east African river basin called Congo basin; which covers an area of 3.7 million square km lies in an astride the equator in west-central Africa-world second largest river basin after Amazon. The Congo River almost pans around republic of Congo, the democratic republic of Congo, the Central African Republic, western Zambia, northern Angola, part of Cameroun, and Tanzania. The remotely sensed imagery analysis and observation revealed that Congo basin is on the elevation of 275 to 460 meters and the Chad basin is on elevation of 240 meters. This implies that water can be drained from Congo basin via headrace down to the Chad basin for the water sustainability.

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Oyerinde, Ganiyu Titilope, Agnide E. Lawin, and Oluwafemi E. Adeyeri. "Multi-variate infilling of missing daily discharge data on the Niger basin." Water Practice and Technology 16, no. 3 (May 28, 2021): 961–79. http://dx.doi.org/10.2166/wpt.2021.048.

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Abstract The Niger basin has experienced historical drought episodes and floods in recent times. Reliable hydrological modelling has been hampered by missing values in daily river discharge data. We assessed the potential of using the Multivariate Imputation by Chained Equations (MICE) to estimate both continuous and discontinuous daily missing data across different spatial scales in the Niger basin. The study was conducted on 22 discharge stations that have missing data ranging from 2% to 70%. Four efficiency metrics were used to determine the effectiveness of MICE. The flow duration curves (FDC) of observed and filled data were compared to determine how MICE captured the discharge patterns. Mann-Kendall, Modified Mann-Kendall, Pettit and Sen's Slope were used to assess the complete discharge trends using the gap-filled data. Results shows that MICE near perfectly filled the missing discharge data with Nash-Sutcliffe Efficiency (NSE) range of 0.94–0.99 for the calibration (1992–1994) period. Good fits were obtained between FDC of observed and gap-filled data in all considered stations. All the catchments showed significantly increasing discharge trend since 1990s after gap filling. Consequently, the use of MICE in handling missing data challenges across spatial scales in the Niger basin was proposed.

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Bader, Jean-Claude, Honoré Dacosta, and Jean-Christophe Pouget. "Seasonal Variations of the Depletion Factor during Recession Periods in the Senegal, Gambia and Niger Watersheds." Water 12, no. 9 (September 9, 2020): 2520. http://dx.doi.org/10.3390/w12092520.

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The daily depletion factor K describes the discharge decrease of rivers only fed by groundwater in the absence of rainfall. In the Senegal, Gambia and Niger river basins in West Africa, the flow recession can exceed 6 months and the precise knowledge of K thus allows discharge forecasts to be made over several months, and is hence potentially interesting for hydraulic structure managers. Seasonal flow recession observed at 54 gauging stations in these basins from 1950 to 2016 is represented by empirical and usual conceptual models that express K. Compared to conventional conceptual models, an empirical model representing K as a polynomial of the decimal logarithm of discharge Q gives better representations of K and better discharge forecasting at horizons from 1 to 120 days for most stations. The relationship between specific discharge Qs and K, not monotonous, is highly homogeneous in some sub-basins but differs significantly between the Senegal and Gambia basins on the one hand and the Niger basin on the other. The relationship K(Q) evolves slightly between three successive periods, with values of K generally lower (meaning faster discharge decrease) in the intermediate period centered on the years 1970–1980. These climate-related interannual variations are much smaller than the seasonal variations of K.

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Abdoulaye, Abdoulaye Oumarou, Haishen Lu, Yonghua Zhu, and Yousef Alhaj Hamoud. "Future Irrigation Water Requirements of the Main Crops Cultivated in the Niger River Basin." Atmosphere 12, no. 4 (March 29, 2021): 439. http://dx.doi.org/10.3390/atmos12040439.

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Precise agricultural predictions of climate change effects on crop water productivity are essential to ensure food security and alleviate water scarcity. In this regard, the present study provides an overview of the future impacts of climate change on the irrigation of agricultural products such as rice, millet, maize, cassava, sorghum, and sugar cane. These crops are some of the most-consumed foodstuffs in countries of the Niger River basin. This study is realized throughout 2020 to 2080, and three Global Climate Models (GCMs) (CSIRO, MIROC5, and ECHAM. MPI-ESM-LR) have been used. The GCMs data have been provided by the IPCC5 database. The irrigation water requirement for each crop was calculated using Smith’s CROPWAT approach. The Penman–Monteith equation recommended by the FAO was used to calculate the potential evapotranspiration. The inter-annual results of the IWR, according to the set of models selected, illustrate that the largest quantities of water used for irrigation are generally observed between January and March, and the lowest quantities are the most often seen between July and September. The majority of models also illustrate a peak in the IWR between March and April. Sorghum and millet are the crops consuming the least amount of water for irrigation; followed by cassava, then rice and corn, and finally sugar cane. The most significant IWRs, which have been predicted, will be between 16.3 mm/day (MIROC5 model, RCP 4.5) and 45.9 mm/day (CSIRO model, RCP 4.5), particularly in Mali, Niger, Algeria, and rarely in Burkina-Faso (CSIRO model, RCP4.5 and 8.5). The lowest IWRs predicted by the models will be from 1.29 mm/day (MIROC5 model, RCP 4.5) to 33.4 mm/day (CSIRO model, RCP 4.5); they will be observed according to the models in Guinea, southern Mali, Ivory Coast, center and southern Nigeria, and Cameroon. However, models predict sugarcane to be the plant with the highest IWR, between 0.25 mm/day (Benin in 2020–2040) and 25.66 mm/day (Chad in 2060–2080). According to the models’ predictions, millet is the crop with the most IWR, between 0.20 mm/day (Benin from 2020 to 2060) and 19.37 mm/day (Chad in 2060–2080). With the results of this study, the countries belonging to the Niger River basin can put in place robust policies in the water resources and agriculture sectors, thus ensuring food security and high-quality production of staple crops, and avoiding water scarcity while facing the negative impacts of climate change.

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Moruff, Adelakun Kehinde, Mu’azu Mohammed Mu’azu, Amali Rosemary Patric, and Omotayo Olabode Lawrence. "Diversity of Phytoplankton Communities in a Tropical River Basin, Nigeria." Hydro Nepal: Journal of Water, Energy and Environment 19 (July 26, 2016): 52–56. http://dx.doi.org/10.3126/hn.v19i0.15353.

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Biological assessment is a useful alternative for understanding the ecological quality of aquatic ecosystems because biological communities integrate the environmental effects of water. This work investigates the diversity and abundance of phytoplankton in the Upper Jebba Basin of the Niger River in Nigeria. We sampled phytoplanktons by dragging plankton nets at three stations from March to May 2015 for qualitative and quantitative samples. Qualitative plankton samples were collected by towing 55μm mesh hydrobios plankton nets just below the water surface for five minutes at each sampling station. Quantitative samples, on the other hand, were collected by filtering 100 litres of water fetched with a bucket through a 55μm mesh hydrobios net. Both samples were preserved separately in a 4% buffered formalin solution. A total of 3160 cells/ml of phytoplanktons from taxa were identified in the study. High dominance of Oscillatoria sp., Microcystis sp., Chlorella sp., Pediastrum sp. and Synendra indicate that this lake has high amount of organic waste, polluted predominantly by upstream concerns (i.e., mining, agricultural, and domestic) and should be monitored strictly by relevant agencies in order to additional reduced health hazards caused by these pollutants.HYDRO Nepal JournalJournal of Water, Energy and EnvironmentIssue: 19Page: 52-56

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Oguntunde, Philip G., Babatunde J. Abiodun, and Gunnar Lischeid. "A numerical modelling study of the hydroclimatology of the Niger River Basin, West Africa." Hydrological Sciences Journal 61, no. 1 (November 3, 2015): 94–106. http://dx.doi.org/10.1080/02626667.2014.980260.

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35

Aich, Valentin, Stefan Liersch, Tobias Vetter, Samuel Fournet, Jafet C. M. Andersson, Sandro Calmanti, Frank H. A. van Weert, Fred F. Hattermann, and Eva N. Paton. "Flood projections within the Niger River Basin under future land use and climate change." Science of The Total Environment 562 (August 2016): 666–77. http://dx.doi.org/10.1016/j.scitotenv.2016.04.021.

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36

Stohl, Andreas, and Paul James. "A Lagrangian Analysis of the Atmospheric Branch of the Global Water Cycle. Part II: Moisture Transports between Earth’s Ocean Basins and River Catchments." Journal of Hydrometeorology 6, no. 6 (December 1, 2005): 961–84. http://dx.doi.org/10.1175/jhm470.1.

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Abstract A diagnostic Lagrangian method to trace the budgets of freshwater fluxes, first described in Part I of this article, is used here to establish source–sink relationships of moisture between earth’s ocean basins and river catchments. Using the Lagrangian particle dispersion model FLEXPART, driven with meteorological analyses, 1.1 million particles, representing the mass of the atmosphere, were tracked over a period of 4 yr. Via diagnosis of the changes of specific humidity along the trajectories, budgets of evaporation minus precipitation (E − P) were determined. For validation purposes, E − P budgets were calculated for 39 river catchments and compared with climatological streamflow data for these rivers. Good agreement (explained variance 87%) was found between the two quantities. The E − P budgets were then tracked forward from all of earth’s ocean basins and backward from the 39 major river catchments for a period of 10 days. As much previous work was done for the Mississippi basin, this basin was chosen for a detailed analysis. Moisture recycling over the continent and moisture transport from the Gulf of Mexico were identified as the major sources for precipitation over the Mississippi basin, in quantitative agreement with previous studies. In the remainder of the paper, global statistics for source–sink relationships of moisture between the ocean basins and river catchments are presented. They show, for instance, the evaporative capacity of monsoonal flows for precipitation over the Ganges and Niger catchments, and the transport of moisture from both hemispheres to supply the Amazon’s precipitation. In contrast, precipitation in northern Eurasia draws its moisture mainly via recycling over the continent. The atmospheric transport of moisture between different ocean basins was also investigated. It was found that transport of air from the North Pacific produces net evaporation over the North Atlantic, but not vice versa. This helps to explain why the sea surface salinity is higher in the North Atlantic than in the North Pacific, a difference thought to be an important driver of the oceans’ thermohaline circulation. Finally, limitations of the method are discussed and possible future developments are outlined.

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37

Ladokun, LL, KR Ajao, and BF Sule. "Regional Scale Assessment of the Gross Hydrokinetic Energy Potentials of Some Rivers in Lower Niger River Basin, Nigeria." Nigerian Journal of Technology 34, no. 2 (March 31, 2015): 421. http://dx.doi.org/10.4314/njt.v34i2.29.

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38

Abiodun, Ajiboye, A. O. Adekunmi, and O. A. Adeleke A. O. Awoyemi. "Impact of Land Right Arrangements on the use of Irrigation Resources in the Lower Niger River Basin Development Authority of Nigeria." International Journal of Trend in Scientific Research and Development Volume-3, Issue-3 (April 30, 2019): 637–41. http://dx.doi.org/10.31142/ijtsrd22927.

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39

Morrison, Brian P., and Daniel J. Moore. "First Occurrence of a Juvenile Chain Pickerel (Esox niger) in Ontario Waters of Lake Ontario." Canadian Field-Naturalist 131, no. 4 (May 23, 2018): 331–34. http://dx.doi.org/10.22621/cfn.v131i4.1946.

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This paper documents the first juvenile Chain Pickerel (Esox niger) captured in Ontario waters of Lake Ontario. It was found during August 2016 monitoring activities at Port of Newcastle. Its occurrence represents a significant westward range expansion from recently documented adults in the eastern basin of Lake Ontario/Bay of Quinte/St. Lawrence River, likely colonizing from United States waters of Lake Ontario.

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40

Silva, AMO, M. Tavares-Dias, GT Jerônimo, and ML Martins. "Parasite diversity in Oxydoras niger (Osteichthyes: Doradidae) from the basin of Solimões River, Amazonas state, Brazil, and the relationship between monogenoidean and condition factor." Brazilian Journal of Biology 71, no. 3 (August 2011): 791–96. http://dx.doi.org/10.1590/s1519-69842011000400026.

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This study describes the parasitic fauna of Oxydoras niger from the Coari Lake, tributary of the medium Solimões River, State of Amazonas, Brazil, and the relationship between the number of Monogenoidea and the condition factor. From a total of 27 examined fish, 70.3% were parasitised by at least one parasite species as follows: Ichthyophthirius multifiliis (Protozoa), Chilodonella sp. (Protozoa), Cosmetocleithrum gussevi, C. confusus, C. parvum and Cosmetocleithrum sp. (Monogenoidea), Paracavisona impudica (Acanthocephala), Cucullanus grandistomis (Nematoda), Proteocephalus kuyukuyu (Cestoda) and Dadaytrema sp. (Digenea). Monogenoidea helminthes were the most prevalent parasite when compared to protozoan and intestinal helminthes. This study showed that O. niger has a great parasite diversity composed mainly of monogenoideans followed by acanthocephalan and digenean. This is the first record of Dadaytrema in O. niger from the Brazilian Amazon. There was a positive correlation between the number of monogenoideans and the condition factor (Kn) of fish, and with this mean intensity of infection, fish welfare was not affected.

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41

Vivian Anyiam, Ifeoma, and Thomas Ohwofasa Ikpesu. "Microbiological quality and biochemical composition of water snail (Pachymelania byronensis) of lower Niger River basin." Emergent Life Sciences Research 4, no. 2 (2018): 1–10. http://dx.doi.org/10.31783/elsr.2018.420110.

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Oluwasegun, Adebayo H. "Flood risk and vulnerability mapping of settlements within upper and lower Niger river basin, Nigeria." Ethiopian Journal of Environmental Studies and Management 9, no. 1 (January 12, 2017): 815. http://dx.doi.org/10.4314/ejesm.v9i1.2s.

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43

Oguntunde, Philip G., Babatunde J. Abiodun, Gunnar Lischeid, and Christoph Merz. "Modelling the impacts of reforestation on the projected hydroclimatology of Niger River Basin, West Africa." Ecohydrology 7, no. 1 (November 8, 2012): 163–76. http://dx.doi.org/10.1002/eco.1343.

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44

Ward, John, and David Kaczan. "Challenging Hydrological Panaceas: Water poverty governance accounting for spatial scale in the Niger River Basin." Journal of Hydrology 519 (November 2014): 2501–14. http://dx.doi.org/10.1016/j.jhydrol.2014.05.068.

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45

Okpara, D. A., and M. B. Offiong. "Morphodynamics of river and coastal transport of sediments in mega delta basin, Niger Delta Nigeria." IOP Conference Series: Earth and Environmental Science 424 (January 27, 2020): 012010. http://dx.doi.org/10.1088/1755-1315/424/1/012010.

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46

Badou, Djigbo Félicien, Bernd Diekkrüger, Evison Kapangaziwiri, Mamadou L. Mbaye, Yacouba Yira, Emmanuel A. Lawin, Ganiyu T. Oyerinde, and Abel Afouda. "Modelling blue and green water availability under climate change in the Beninese Basin of the Niger River Basin, West Africa." Hydrological Processes 32, no. 16 (July 8, 2018): 2526–42. http://dx.doi.org/10.1002/hyp.13153.

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47

López, Oliver, Rasmus Houborg, and Matthew Francis McCabe. "Evaluating the hydrological consistency of evaporation products using satellite-based gravity and rainfall data." Hydrology and Earth System Sciences 21, no. 1 (January 18, 2017): 323–43. http://dx.doi.org/10.5194/hess-21-323-2017.

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Abstract. Advances in space-based observations have provided the capacity to develop regional- to global-scale estimates of evaporation, offering insights into this key component of the hydrological cycle. However, the evaluation of large-scale evaporation retrievals is not a straightforward task. While a number of studies have intercompared a range of these evaporation products by examining the variance amongst them, or by comparison of pixel-scale retrievals against ground-based observations, there is a need to explore more appropriate techniques to comprehensively evaluate remote-sensing-based estimates. One possible approach is to establish the level of product agreement between related hydrological components: for instance, how well do evaporation patterns and response match with precipitation or water storage changes? To assess the suitability of this consistency-based approach for evaluating evaporation products, we focused our investigation on four globally distributed basins in arid and semi-arid environments, comprising the Colorado River basin, Niger River basin, Aral Sea basin, and Lake Eyre basin. In an effort to assess retrieval quality, three satellite-based global evaporation products based on different methodologies and input data, including CSIRO-PML, the MODIS Global Evapotranspiration product (MOD16), and Global Land Evaporation: the Amsterdam Methodology (GLEAM), were evaluated against rainfall data from the Global Precipitation Climatology Project (GPCP) along with Gravity Recovery and Climate Experiment (GRACE) water storage anomalies. To ensure a fair comparison, we evaluated consistency using a degree correlation approach after transforming both evaporation and precipitation data into spherical harmonics. Overall we found no persistent hydrological consistency in these dryland environments. Indeed, the degree correlation showed oscillating values between periods of low and high water storage changes, with a phase difference of about 2–3 months. Interestingly, after imposing a simple lag in GRACE data to account for delayed surface runoff or baseflow components, an improved match in terms of degree correlation was observed in the Niger River basin. Significant improvements to the degree correlations (from ∼ 0 to about 0.6) were also found in the Colorado River basin for both the CSIRO-PML and GLEAM products, while MOD16 showed only half of that improvement. In other basins, the variability in the temporal pattern of degree correlations remained considerable and hindered any clear differentiation between the evaporation products. Even so, it was found that a constant lag of 2 months provided a better fit compared to other alternatives, including a zero lag. From a product assessment perspective, no significant or persistent advantage could be discerned across any of the three evaporation products in terms of a sustained hydrological consistency with precipitation and water storage anomaly data. As a result, our analysis has implications in terms of the confidence that can be placed in independent retrievals of the hydrological cycle, raises questions on inter-product quality, and highlights the need for additional techniques to evaluate large-scale products.

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Ekeu-wei, Iguniwari, George Blackburn, and Philip Pedruco. "Infilling Missing Data in Hydrology: Solutions Using Satellite Radar Altimetry and Multiple Imputation for Data-Sparse Regions." Water 10, no. 10 (October 20, 2018): 1483. http://dx.doi.org/10.3390/w10101483.

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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.

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Picouet, C., B. Hingray, and J. C. Olivry. "Empirical and conceptual modelling of the suspended sediment dynamics in a large tropical African river: the Upper Niger river basin." Journal of Hydrology 250, no. 1-4 (September 2001): 19–39. http://dx.doi.org/10.1016/s0022-1694(01)00407-3.

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50

Pedinotti, V., A. Boone, B. Decharme, J. F. Crétaux, N. Mognard, G. Panthou, F. Papa, and B. A. Tanimoun. "Evaluation of the ISBA-TRIP continental hydrologic system over the Niger basin using in situ and satellite derived datasets." Hydrology and Earth System Sciences 16, no. 6 (June 26, 2012): 1745–73. http://dx.doi.org/10.5194/hess-16-1745-2012.

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Abstract. During the 1970s and 1980s, West Africa has faced extreme climate variations with extended drought conditions. Of particular importance is the Niger basin, since it traverses a large part of the Sahel and is thus a critical source of water for an ever-increasing local population in this semi arid region. However, the understanding of the hydrological processes over this basin is currently limited by the lack of spatially distributed surface water and discharge measurements. The purpose of this study is to evaluate the ability of the ISBA-TRIP continental hydrologic system to represent key processes related to the hydrological cycle of the Niger basin. ISBA-TRIP is currently used within a coupled global climate model, so that the scheme must represent the first order processes which are critical for representing the water cycle while retaining a limited number of parameters and a simple representation of the physics. To this end, the scheme uses first-order approximations to account explicitly for the surface river routing, the floodplain dynamics, and the water storage using a deep aquifer reservoir. In the current study, simulations are done at a 0.5 by 0.5° spatial resolution over the 2002–2007 period (in order to take advantage of the recent satellite record and data from the African Monsoon Multidisciplinary Analyses project, AMMA). Four configurations of the model are compared to evaluate the separate impacts of the flooding scheme and the aquifer on the water cycle. Moreover, the model is forced by two different rainfall datasets to consider the sensitivity of the model to rainfall input uncertainties. The model is evaluated using in situ discharge measurements as well as satellite derived flood extent, total continental water storage changes and river height changes. The basic analysis of in situ discharges confirms the impact of the inner delta area, known as a significant flooded area, on the discharge, characterized by a strong reduction of the streamflow after the delta compared to the streamflow before the delta. In the simulations, the flooding scheme leads to a non-negligible increase of evaporation over large flooded areas, which decreases the Niger river flow by 15% to 50% in the locations situated after the inner delta as a function of the input rainfall dataset used as forcing. This improves the simulation of the river discharge downstream of the delta, confirming the need for coupling the land surface scheme with the flood model. The deep aquifer reservoir improves Niger low flows and the recession law during the dry season. The comparison with 3 satellite products from the Gravity Recovery and Climated Experiment (GRACE) shows a non negligible contribution of the deeper soil layers to the total storage (34% for groundwater and aquifer). The simulations also show a non negligible sensitivity of the simulations to rain uncertainties especially concerning the discharge. Finally, sensitivity tests show that a good parameterization of routing is required to optimize simulation errors. Indeed, the modification of certain key parameters which can be observed from space (notably river height and flooded zones height changes and extent) has an impact on the model dynamics, thus it is suggested that improving the model input parameters using future developments in remote sensing technologies such as the joint CNES-NASA satellite project SWOT (Surface Water Ocean Topography), which will provide water heights and extentat land surface with an unprecedented 50–100 m resolution and precision.

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