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The impact of climate change on precipitation and water availability is of major concern for policy makers in the Mono Basin of West Africa, whose economy mainly depends on rainfed agriculture and hydropower generation. The objective of this study is to project rainfall, flows and evapotranspiration (ET) in the future period and understand their changes across Mono River Basin. Observed data were considered for the historical period 1980–2010, and a Multi-model ensemble for future projections data of eight selected Regional Climate Models under RCP 4.5 and RCP 8.5 over the periods 2011–2100 was used. The GR4J model was used to simulate daily flows of the Mono watershed. The ensemble mean shows a decrease and increase streamflows between -54 % and 42 %, -58 % and 31 %​​​​​​​ under the RCP4.5, RCP8.5 scenario, respectively. The greatest decreases of high flows is projected to occur in the near term under RCP8.5, whereas the greatest decrease of low flows is projected to occur in the long term under the same RCP. For the rainfall and ET, the both scenarios (RCP4.5 and RCP8.5) predict an increase of ET while the rainfall will decrease. The results of this study of would be very useful in the choice of management and adaptation policies for water resources management. [ABSTRACT FROM AUTHOR]

The coastal zones are areas where a very high number of lagoon-marine species reproduce, grow or transit, which are most often the object of halieutic exploitation. The present study aims to analyze the risk of contamination of fisheries ecosystems and its consequences on the evolution of aquatic resources in the coastal zone, more precisely from southwest Benin to southeast Togo. The methodology adopted is based on the collection and processing of raw data such as: hydrometric data, granulometric data, climatological data, data from fauna and flora inventories, completed by those from in situ measurements and those from laboratory analyses made from sediment samples and some species caught during fishing activities during the different hydrological seasons. The analysis of the results revealed that the pollution of the lagoon channel in Cd, As, Pb and some major ions such as Cl - , NO 3- and PO 43- are responsible for its eutrophication. Furthermore, organic matter and high concentrations of SS lead to the covering of aquatic environments, particularly spawning grounds and the smothering of eggs through the reduction of essential metabolic exchanges (oxygen and nutrient supply, evacuation of metabolic waste) through the reduction of the concentration of dissolved oxygen within the substrate. Trace element analysis in the flesh of Captain (Polydactylus quadrifilis), white grouper (Epinephelus aeneus), tilefish (Tilapia zillii), and white catfish samples revealed their trace element contamination levels. Behavioral effects (abandonment of shelter areas and avoidance reaction); sublethal effects (short-term reduction in feeding rate; minor physiological stress; increase in coughing frequency; increase in the breathing rhythm; moderate physiological stress; major; delayed hatching; reduced number of fish; mortality) were recorded. According to 89 % of the fishermen, the decrease of the fished fish species is registered during the dry periods, when the channel has a high level of contaminating heavy metals and major ions. [ABSTRACT FROM AUTHOR]

Runoff simulation in highly anthropized catchments is complex, but essential for water management, especially in poorly gauged and data-scarce hydrosystems of the West African Sahel. This study aims to evaluate the effect of different calibration schemes on runoff simulation. The physically-based and semi-distributed hydrological SWAT (Soil and Water Assessment Tool) model is used to simulate daily runoff in the Nakanbé catchment at Wayen station in Burkina Faso (in the West African Sahel) over the period 2006–2012. Four (4) hydrometric stations (Dombré, Rambo, Ramsa and Wayen) gauging 4 nested catchments (ranging from 1060 to 21 178 km 2 in size) are considered. The added value of the consideration of nested catchments is assessed through the following 3 calibration schemes: one-site (OS) at the entire catchment outlet (Wayen); multi-sites with nested sub-catchments (MS1); and multi-sites without considering nested sub-catchments (MS2). The results indicate that OS and MS2 schemes perform well (KGE > 0.7, | PBIAS |<3 %), with MS2 scheme being superior (KGE, PBIAS). However, the MS1 scheme (KGE = 0.68; PBIAS = -22.9 %) performed worse in comparison to the traditional OS scheme. The comparison of the three modelling schemes provides evidence that accounting for nested sub-catchments does not necessarily improve the quality of rainfall-runoff simulations. Yet, multi-site calibration should be favoured when catchments are not nested. [ABSTRACT FROM AUTHOR]

This study was carried out in the White Bandama watershed (WBW) in Côte d'Ivoire (West Africa). The objective is to assess the impacts of future climate change (CC) on the hydropower potential (HPP) of the WBW. The methodology is based on coupling the SWAT (Soil and Water Assessment Tool) hydrological model with the Geographic Information System (GIS) QGIS to assess HPP on streams and evaluate the impacts of future CC on HPP of the watershed. Historical and climate projection data (precipitation, minimum and maximum temperature) for a set of three Regional Climate Models (RCM) from CORDEX-AFRICA (CCCma-CanRCM4, CCLM4-8-17 and REMO 2009) under RCP 4.5 were used. The biases of the ensemble mean were corrected by the Delta-change method. The relative change of streamflow discharge and HPP was assessed as the relative difference between the projection periods (2041–2070 and 2071–2100) and the reference period (1976–2005). The results showed a total of 22 future hydropower potential sites in the watershed. These sites were identified, geolocated and classified according to their potential capacity of generation in 82 % as small (1–25 MW potential capacity), 9 % as medium (25–100 MW potential capacity) and 9 % as large (more than 100 MW potential capacity) hydropower. The climate models' ensemble projected an upward trend for both the annual mean discharge of rivers and HPP of the WBW according to RCP 4.5 for the periods 2041–2070 and 2071–2100. On the annual cycle, the months of August and September will record the highest monthly mean flows between 150 and 200 m 3 s -1 while the months from November to April will record low monthly mean flows in the WBW. [ABSTRACT FROM AUTHOR]

Due to pronounced hydroclimatic fluctuations and rapid urban growth, coastal lagoonal systems in the Southern Mediterranean semi-arid areas undergo pronounced shoreline retreats and increased coastal floodings. The socioeconomic impacts of these alarming coastal changes remain poorly uncharacterized. To address this deficiency, we calculate the Socioeconomic Vulnerability Index (SVI) based on the decadal changes in shoreline retreat and land use occupation considering the study case of the coastal lagoon of Ghar El Melh in Tunisia which is representative of several lagoonal systems in the southern Mediterranean basin. We first monitor the diachronic shoreline changes from 1882 to 2016 using aerial and orbital photogrammetric scenes combined with topographic and bathymetric maps. Using the Digital Shoreline Analysis System (DSAS) and historic bathymetric records, we then measure the changes in shoreline position from 1882 to 2016. Secondly, the above is correlated with the Land Use/Land Cover (LULC) assessment using a supervised classification algorithm from multiple Landsat 5-8 orbital photogrammetric scenes. We assess the SVI using five socioeconomic parameters: (1) population density, (2) land use change, (3) road network, and (4) settlements. Our results reveal the occurrence of severe coastal erosion with a maximum Net Shoreline Movement of -1580 m (±6 m) between 1882 and 2016. Moreover, the changes in land use from 1985 to 2021 reveal the extension in urban growth around the lagoon, rising from 5.4 % to 13.5 %. Whereas the vegetation coverage is decreasing by 9 % over the same period. The resulting SVI map reveals that 85 % of the lagoon area is characterized by high to very high vulnerability. This high coastal vulnerability is found to be primarily due to the extensive change in land occupation over the last few decades and is aggravated by the increase in hydroclimatic extremes. [ABSTRACT FROM AUTHOR]

This study investigated drought and flooding changes in West Africa between 1983–2012 and projected near future (2025–2054) periods. The datasets used are the CHIRTS and CHIRPS-2 for observed reanalysis and five (05) models of ISIMIP2b for Shared Socio-economic Pathways (SSP1.2-6 and SSP5-8.5). Extremely and very wet days total precipitation (R95pTOT; R99pTOT) and Standardized Precipitation Evapotranspiration Index (SPEI) were employed to investigate floods and drought spatial distribution using Sen Slope trend analysis method. The results showed that there is a variability in the spatial distribution of extreme indices with an upward and downward trend of dry and wet rainfall periods in West Africa in both historical and projected periods. This observation suggests that the study area is faced with rainfall variability marked by extreme events. A further examination on the spatial and temporal distribution of flood occurrence showed that more flood events were observed in the Gulf of Guinea and Savannah countries, followed by an increase in uniform spatial distribution and moderate wet days both under SSP1.2.6, and SSP 5.8.5. In addition, result showed that an upward trend in wet periods can cause the occurrence of extreme events associated with floods in the context of global warming. However, with these scenarios negative changes are not excluded in the East, the Sahel and some western part of the Gulf of Guinea in the study area for the SSP5.8.5 scenario. Thus, the results revealed that the spatio- temporal variability of extreme rainfall can have repercussions on the hydrological functioning of watersheds, water availability and water-dependent activities. [ABSTRACT FROM AUTHOR]

Many hydrological applications employ conceptual-lumped rainfall-runoff models to support water resource management techniques. Because of their ability to exploit minimal data and provide enough credible information, they provide an edge in data-scarce domains. The purpose of this research is to evaluate the feasibility of using multiple rainfall-runoff hydrologic models Génie Rural à 4, 5, 6 paramètres Journalier (GR4J, GR5J, and GR6J) in the Upper Benue River (UBR) in Northern Cameroon. The models were calibrated using Michel's calibration algorithm implemented in airGR packages, while considering different objective functions (NSE, KGE, composite criterion). The objective here was to find the optimum objective function that takes into account the various components of the hydrographs in this watershed and to assess the impact of the chosen objective function on parameter optimization. The results reveal that the model performance as well as the optimized parameters of the different GR models vary according to the selected objective function. According to the study, adopting the composite criterion as an objective function during model calibration improves model accuracy. The model's performance reveals that two of the three models (GR5J and GR6J) reproduced the discharge well in the considered catchment, with NSE and KGE greater than 0.62 during the model validation. This highlights how these two GR models can be applied to various water management concerns in the UBR. [ABSTRACT FROM AUTHOR]

The Ouémé River basin extends over almost half of Benin's territory, entirely located in a humid tropical climate. This river system includes a deltaic zone (delta of the Ouémé) known for its high agricultural potential and thus subject to a socio-economic development agenda. The Ouémé delta is facing recurrent floods that maintain rural agricultural population into a retrograding crisis with significant damages such as losses of properties. The objective of this study is to improve decision-making in the Ouémé basin through the simulation of exceptional floods using the HEC-RAS model. The HEC RAS model is a conceptual model, which works through mathematical and physical formulas to implement environmental phenomena for forecasting, understanding and analysis purposes. The model inputs used are basin GIS data, hydro-meteorological data, characteristics of existing hydraulic structures, etc. The targeted outputs include 1D/2D/3D view plans with support of satellite images, tables, graphs and curves. It is worth mentioning that the model provides outputs compatible with other tools, such as civil engineering (Civil 3D, Revit, Infraworks, etc.) and GIS, that help to expand the valorization fields. The implementation of the model in the Ouémé basin has made it possible to note: (i) that the recurring effect of losses and damages is justified by the settlement of the population on the river banks; (ii) that there is an important agricultural production in areas of high flood risk; (iii) that depending on the occurrence of the phenomenon, the flooded extent and the height of submersion remains variable, and more important for extreme flooding; (iv) about 12.07 % occurrence of river flood against 13.24 % for flash flood at a return period of 30 years. Moreover, it is very relevant to note that most of flood waters converge to the western part of the basin (an area with a low risk of flooding, stretched over 63.68 km 2) and to the eastern part around the Damè-Wogon depression (an area at high risk of flooding, stretched over 10.49 km 2). [ABSTRACT FROM AUTHOR]

Copyright of Proceedings of the International Association of Hydrological Sciences (PIAHS) is the property of Copernicus Gesellschaft mbH and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The FRIEND-Water program (FWP) is the oldest and the most transverse program (i.e. Flagship Initiative) within the Hydrological Intergovernmental Program (IHP) from UNESCO. FRIEND means "Flow Regimes from International and Experimental Network Data". The FWP is dedicated to allow large communities of hydrologists and associated disciplines to collaborate across borders on common shared data and scientific topics which are addressed through large world regions. The program has evolved in its 35 years of existence. There are 8 large regions in the world which gather tenths of hundreds of researchers, and organize events following several research topics defined according to each region priorities. The FWP is chaired by a scientific committee gathering regional coordinators and thematic experts. Each region gives its research priorities which evolve according to the projections given by the member States during the IHP council every year. The future activities of the FWP are defined by the upcoming IHP IX program and with the support of the newly created Montpellier UNESCO Category II Center ICIREWARD, acting as FWP Secretariat. [ABSTRACT FROM AUTHOR]

This study aims to assess simulated surface runoff before and after dam construction in the Mono catchment (West Africa) using two lumped models: GR4J (Rural Engineering with 4 Daily Parameters) and IHACRES (Identification of unit Hydrographs and Component flows from Rainfall, Evapotranspiration and Stream data) over two different periods (1964–1986 and 1988–2010). Daily rainfall, mean temperature, evapotranspiration and discharge in situ data were collected for the period 1964–2010. After the model's initialization, calibration and validation; performances analysis have been carried out using multi-objectives functions developed in R software (version 3.5.3). The results indicate that statistical metrics such as the coefficient of determination (R2), the Kling–Gupta Efficiency (KGE), the Nash–Sutcliffe coefficient (NSE) and the Percent of Bias (PBIAS) provide satisfactory insights over the first period of simulation (1964–1986) and low performances over the second period of simulation (1988–2010). In particular, IHACRES model underestimates extreme high runoff of Mono catchment between 1964 and 1986. Conversely, GR4J model overestimates extreme high runoff and has been found to be better for runoff prediction of the river only between 1964 and 1986. Moreover, the study deduced that the robustness of runoff simulation between 1964 and 1986 is better than between 1988 and 2010. Therefore, the weakness of simulated runoff between 1988 and 2010 was certainly due to dam management in the catchment. The study suggests that land cover changes impacts, soil proprieties and climate may also affect surface runoff in the catchment. [ABSTRACT FROM AUTHOR]

The objective of this study is to model the Mono River basin at Athiémé using stochastic approach for a better knowledge of the hydrological functioning of the basin. Data used in this study consist of observed precipitation and temperature data over the period 1961–2012 and future projection data from two regional climate models (HIRHAM5 and REMO) over the period 2016–2100. Simulation of the river discharge was made using ModHyPMA, GR4J, HBV, AWBM models and uncertainties analysis were performed by a stochastic approach. Results showed that the different rainfall-runoff models used reproduce well the observed hydrographs. However, the multi-modelling approach has improved the performance of the individual models. The Hermite orthogonal polynomials of order 4 are well suited for the prediction of flood flows in this basin. This stochastic modeling approach allowed us to deduce that extreme events would therefore increase in the middle of the century under RCP8.5 scenario and towards the end of the century under RCP4.5 scenario. [ABSTRACT FROM AUTHOR]

Hydropower energy, the main renewable energy source in West Africa, contributes to more than half of the Togo and Benin National electrification. This resource highly depends on water availability in rivers or reservoirs. The water availability heavily relies on climate patterns of the area. In the climate change context, the sustainability of hydropower plants is at risk. This work aims to assess the sensitivity of the Nangbeto hydropower plant to multiyear climate variability using statistical analysis. The results show that energy generation at Nangbeto hydropower is more modulated by four main variables namely inflow to reservoir, water level, rainfall of the actual and the previous year. The energy generation is found to be strongly and significantly correlated to inflow to reservoir, water level, and rainfall. Overall, the Nangbeto hydropower generation is more sensitive to inflow which is controlled by climate variables (rainfall, temperature) and land use/cover change. Therefore, the probable future change in these variables is suggested to be deeply investigated. [ABSTRACT FROM AUTHOR]

Nowadays, special attention is paid to hydroelectric production because it is an efficient, reliable, and renewable source of energy, especially in developing countries like Cameroon, where hydropower potential is the main source of electricity production. It also represents a useful tool to reduce the atmospheric greenhouse gas concentrations caused by human activities. However, it is the most sensitive industry to global warming, mainly because climate change will directly affect the quality, quantity of water resources (streamflow and runoff), which are the important drivers of hydropower potential. This study examined the response of hydropower potential to climate change on the Lagdo dam located in the Benue River Basin, Northern Cameroon. Hydropower potential was computed based on streamflow simulated using HBV-Light hydrological model with dynamically downscaled temperature and precipitation from the regional climate model REMO. These data were obtained using the boundary conditions of two general circulation models (GCMs): the Europe-wide Consortium Earth System Model (EC-Earth) and the Max Planck Institute-Earth System Model (MPI-ESM) under three Representative Concentrations Pathways (RCP2.6, RCP4.5 and RCP8.5). The results suggest that, the combination of decreased precipitation and streamflow, increased PET will negatively impact the hydropower potential in the Lagdo dam under climate change scenarios, models and future periods. [ABSTRACT FROM AUTHOR]

This study addresses the importance of integrating the effect of land use on soil infiltration rate into land use change impact modeling. Based on a validated version 9.05.04 of the Water balance Simulation Model-WaSiM (statistical quality measures > 0.7), and field measurement of the infiltration rate under cropland and fallow, sixteen model simulations were performed. The impact of land use change is computed comparing LULC status of years 1990 and 2013. The effect of soil parameterization is computed using a refined soil map integrating land use change impact of soil infiltration rate and a classic soil map not considering this interaction. The results show differences in model results as an effect of soil parameterization approaches, indicating that the model is sensitive to the integration of LULC related effects on soil hydraulic conductivity. These differences are more pronounced with increasing modeling time steps (24 and 28 h). The signal-to-noise-ratio indicates that, results achieved in LULC impact assessment with a classic and a refined soil parameterization are very comparable except for interflow. [ABSTRACT FROM AUTHOR]

Copyright of Proceedings of the International Association of Hydrological Sciences (PIAHS) is the property of Copernicus Gesellschaft mbH and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Proceedings of the International Association of Hydrological Sciences (PIAHS) is the property of Copernicus Gesellschaft mbH and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Floods are natural disasters that widely affect people and goods. Its frequency and magnitude are projected to substantially increase due to the ongoing environmental change. At regional and national levels, some efforts have been made in predicting floods at a short-term range. However, the usefulness of flood prediction increases as the time lead increases. The objective of this work is therefore to investigate flood sensitivity to climate indexes in West Africa as a basis for seasonal flood forecasting. The methodology consists of optimizing the relationship between Annual Maximal Discharge (AMD), a proxy for flood discharge and various climate indexes using correlation coefficient, linear regression and statistical modeling based on 56 river gauging stations across West Africa. The climate indexes considered are the Sea Surface Temperature (SST) of the Tropical Northern Atlantic (TNA), SST of the Tropical Southern Atlantic (TSA), the Sea Level Pressure (SLP) of the Southern Oscillation Indexes (SOI) and the detrended El-Nino Southern Oscillation indexes. It was found that SOI/SLP indexes are the most strongly related to the AMD for the investigated stations with generally high, positive, and statistically significant correlation. The TSA/SST indexes indicated both positive and negative statistically significant correlations with river discharge in the region. The percentage change in AMD per unit change in SOI/SLP for most of the statistically significant stations is within 10 % and 50 % indicating a strong relationship between these two variables. This relationship could serve as a basis for seasonal flood forecasting in the study area. [ABSTRACT FROM AUTHOR]

The Ouémé watersheds at Bétérou and Bonou has been recently facing increased sensitivity to extreme hydroclimatic phenomena that occurred by flooding or drought events. In the same time, the population growth and the related socio-economic activities increased the pressure state on water resources. In this context, hydrological modeling is an important issue and this study aims at analyzing the calibration of the hydrological model GR4J based on PET Penman-Monteith and Oudin methods. Daily rainfall, Penman-Monteith and Oudin evapotranspiration and daily data flow from the Bétérou and Bonou hydrometric stations on the Ouémé Basin have been implemented in the GR4J model over the period 1971 to 2010. Oudin PET values are slightly higher than the Penman-Monteith PET ones. However, the difference between the two PET methods have only few impacts on the optimization and performance criteria of the GR4J model. The Nash values ranges from 0.83 to 0.91 in Bonou, and 0.52 to 0.70 in Bétérou for the calibration in dry period, while in validation, they are 0.59 to 0.78 in Bétérou, and 0.56 to 0.88 in Bonou in wet season. In view of these results, with the two PET methods used which do not result from the same climatic variables, it should be said that the formulation of PET has only few impacts on the results of GR4J for these tropical basins. [ABSTRACT FROM AUTHOR]

Tropical moist ecosystems, such as Ahémé lake, south-west Benin, are increasingly marked by water degradation, linked with the activities of increasing riparian populations. The objective of this study is to analyze sedimentary dynamics and its influence on the changing ecosystem of Ahémé lake from 1961-2010. Data used to carry out the study are records of precipitation, flows, turbidity, suspended sediment, mineral elements and bathymetry. Grain size data from the sieving of sediment samples were used to interpret suspended solids distribution in the lake. Linear correlation coefficients were used to assess the degree of dependence between rainfall and runoff inputs to the lake. Lake depth measurements in some areas of the lake serve to determine the rate of infilling. The sorting index was used to highlight the distribution and origin of sediments in the lake. The results show a degradation of the lake Ahémé ecosystem characterized by infilling of its bed, a high correlation (r D 0:90) between rainfall and runoff, seasonal change in physicochemical parameters (total suspended sediment decrease by -91 %) and decrease in fish production by 135.8 t yr-1. The highest mean suspended sediment concentrations in lake inputs occur during high water periods (123 mgL-1) compared to low water periods (11.2 mgL-1). [ABSTRACT FROM AUTHOR]