In West Africa, the drinking water supply relies on the hard-rock aquifers. In Ivory Coast, the population growth along with the climate changes make drinking water resources highly vulnerable. The ...White Bandama upstream watershed in northern Ivory Coast is located on a fissured hard-rock aquifer and is poorly known, both in the geometry of the reservoirs and in the hydrogeological potential of the reserves it contains. Indeed, the heterogeneous subsurface in this region shows high variability in the hydraulic conductivity inducing difficulties in the hydrogeological exploration. The determination of the geometry and hydrodynamic properties of the aquifer are required for a sustainable management of this water resource and for a better choice of future well locations. This study presents a hydrogeophysical approach using the multifrequency electromagnetic device PROMISR, as well as lithology logs and geological information of a 30×30 km zone in the northwestern part of the White Bandama catchment. Our geophysical data are interpreted with 1D multi-layer models consistent with the discontinuities observed in lithology logs and the geology of the site. Results allow to precise the local thicknesses of the 3 main units of our study area down to 50 m, being from top to down, saprolite (which is often indured close to the surface), fissured-rock zone and rock substratum. Between the saprolite and the fissured zone, the main aquifer unit constitutes the interesting target for productive water wells. Its thickness ranges from 15 to 30 m. A detailed knowledge of the local aquifer geometry constitutes the first and crucial step before going further into a complete hydrogeological study.
In the context of climate change in West Africa characterized by a reduction of precipitation, this study was conducted to evaluate the impact of climate change on water resources from now to the end ...of the 21st century in the transboundary watershed of the Sassandra River shared by Guinea and Côte d’Ivoire. Historical and future climate data of Representative Concentration Pathways (RCPs) 4.5 and 8.5 were projected with the Abdus Salam International Centre for Theoretical Physics (ICTP) Regional Climate Model (RegCM4). The hydrological modeling of the river basin was carried out with the conceptual hydrological model, GR2M, a monthly time steps model that allows for the assessment of the discharge of the Sassandra River for each climate scenario according to the time periods 2021–2040 (Horizon 2030), 2041–2060 (Horizon 2050), 2061–2080 (Horizon 2050), and 2061–2080 (Horizon 2090). The results show a reduction in annual discharge when compared to the baseline (1961–1980). For RCP 4.5, the observed values go from −1.2% in 2030 to −2.3% in 2070 and rise to −2.1% in 2090. Concerning RCP 8.5, we saw a variation from −4.2 to −7.9% in Horizons 2030 and 2090, respectively. With the general decrease in rainfall in West Africa, it is appropriate to assess the impact on water resources of the largest rivers (Niger, Gambia, and Senegal) that irrigate the Sahelo–Saharian zone.
Access to drinking water and management of water resources are still a real issue in Côte d'Ivoire’s granitic and volcano-sedimentary basement regions. This situation is due to the combination of ...many factors including poor knowledge of hydrogeological environment. The present study assess the fractures’ network that has affected the Precambrian basement aquifer of Divo-Oume area by making a structural mapping and studying the spatial distribution of lineaments. For this purpose, the study exploits the contribution of radar images. Manually and without using directional filters, 7886 lineaments with variables lengths, have been derived from both RADARSAT-1 and ASAR images. The validation approach was based on the comparison between the orientations of the lineaments of the current study and those of the previous ones, and on the analysis of the distance between the nearest lineament and the well. This approach has shown that the lineaments would mostly correspond to fractures and they would be involved in the occurrence of groundwater. The analysis of lineaments orientations distribution revealed heterogeneity of directions and predominance of NW-SE and NE-SW families’ directions. The cumulative lineaments density map and one related the number of lineaments cross-points density revealed the spatial heterogeneity of fractures network which seem to be controlled by geomorphology, geological formations and lithology contacts. The results obtained from different thematic maps are useful for the context of setting up of high yield hydraulic drilling programs and the implementation of water resources management tools.
Stratiform fissured layer within basement aquifers has increasingly been tapped because of its good transmissivity and groundwater storage capacity. This study aims to determine the hydrodynamic ...properties and thickness of the fissured layer of granitoids in the Tchologo region where access to drinking water has deteriorated over the years. Statistical analysis of the vertical distribution of the linear discharge from 148 boreholes measured from the length below the base of the saprolites has made it possible to characterize the geometry of fissured layer. The useful thickness of the fissured layer was determined from the 80% percentile method. Linear discharge range from 0.0087 to 0.678 m3 h−1.m−1. The thickness of the most transmissive part of the fissured layer is between 20 and 40 m. The 40 m depth is the useful thickness of the hard-rock aquifer. The mean linear discharge and mean discharge for this useful thickness are 0.129 m3 h−1.m−1 and 5.21 m3.h-1, respectively. These results will improve the success rate of drilling in the region because it will be possible to define the average useful depth of the boreholes to be drilled.
Hard-rock aquifer; Conducive fissures; Fracture connectivity; Groundwater occurrence; Borehole linear discharge; Côte d’Ivoire.
Lineaments analyses are widely included in the selection of groundwater exploration sites. It should also be noted that the junction zones of several fractures are often points of high water flow. ...The purpose is to suggest potential sites for setting water drillings in the Béré region based on drilling flows and fractures. The influence of lineaments and their intersections on groundwater yield was studied using SRTM satellite imagery and borehole flow data. We used the Line Detecting Segment algorithm to extract lineaments and fractures. Then we performed the ordinary kriging of the drilling flows and an Heatmap of the fracture intersection points using Kernel density estimation. The crossing between these two maps showed a good correlation between the flows and the fracture intersections. The SRTM DEM are efficient for fracture extraction. All this has allowed us to characterize the potential sites for setting drilling with good flow rates.
An assessment of hydropower potential at the watershed scale was conducted at the White Bandama Watershed (WBW) in Côte d'Ivoire (West Africa). The method used involves the application of a ...hydrological model Soil and Water Assessment Tool (SWAT) coupled with a Quantum Geographic Information System (QGIS), denoted as QSWAT, to assess the water resource availability and hydropower potential of streams and determine potential hydropower sites for future hydropower development in the watershed. Geospatial data about the topography, soil types, land use/land cover, weather, and discharge were considered in hydrological and hydro-geomorphological characterization of the watershed. Streamflow and climate data-enabled model operation and simulation of the hydrology of the watershed. The model performance and robustness were confirmed with the
p-factor, r-factor
, coefficient of determination R
2
, and Nash–Sutcliffe (NS) efficiency coefficient. The hydropower potential of streams was evaluated by considering the simulated streamflow and water head. A total of 22 future hydropower sites was identified, geolocated, and classified with an estimated total production capacity of 538.56 MW.
The present study was undertaken to characterize the bushfire regime and the climatic factors influencing its propagation in the Bounkani region. Thus, this work analyzes the spatio-temporal dynamics ...of fires and the relationship between climatic variables and pyrological variables. First, it exploits time series of active fires and burned areas from MODIS Active fires (MCD14ML) and MODIS Burned area (MCD60A1) data for the period from 2000 to 2017. The methodology is based on the evaluation of seasonality and fire occurrences, and on the spatio-temporal evolution of fires. The results obtained indicate that, on average, the fire season occurs between the months of November and March, generally corresponding to the dry season. Also, the number of fires and the area burned follow a decreasing trend during the 17 years of study. The months of December and January recorded the highest peaks of burned areas and fire outbreaks respectively. Finally, the analysis of the dependence between climatic variables and pyrological variables by the Pearson correlation method showed the influence of climatic parameters in the outbreak and spread of bushfires in the study area. Precipitation and relative humidity are the best predictors with a negative influence on fire activity, while the positive predictors remain temperature. These variables directly impact fire regime in general. The results of this study will assist policy makers and managers in decision making for the implementation of fire control strategies.
This study analyzes, at local and regional scales, the rainfall variability across the Agneby watershed at the Agboville outlet over the period 1950–2013. Daily rainfall data from 14 rain gauges are ...used. The methods used are based, firstly, on the rainfall index which aims to characterize the inter-annual and decadal variability of rainfall and, secondly, on the moving average to determine the dynamics of the mean seasonal cycle of the precipitations. Furthermore, the Pettitt test and the Hubert segmentation are applied to detect change-point in the rainfall series. At the basin scale, analysis of rainfall signals composites has shown that the rainfall deficit was more pronounced after the leap of monsoon. Dry years were characterized by an early monsoon demise which is remarkable after 1968. Moreover, the years after 1969 presented a shift of the peaks in precipitation for about 12 days. These peaks were reached early. The rainfall signal showed that the rainfall deficit for the period after 1968, relatively to the period before, was 10% in June against 36% in October for the average rainfall in the Agneby basin. At the local scale, the deficit of the peaks depends on the location. These rainfall deficits were 23% against 36.3% in June for the Agboville and Bongouanou rain gauges, respectively.
This study aims to provide improved knowledge and evidence on current (1986–2015) climate variation based on six rainfall indices over five West African countries (Senegal, Niger, Burkina Faso, Ivory ...Coast, and Benin) using the Climate Hazards Group InfraRed Precipitation with Station (CHIRPS) dataset. On average, precipitation has increased over the central Sahel and the western Sahel. This increase is associated with increase in the number of rainy days, longer wet spells and shorter dry spells. Over the Guinea Coast, the slight increase in precipitation is associated with an increase in the intensity of rainfall with a shorter duration of wet spells. However, these mean changes in precipitation are not all statistically significant and uniform within a country. While previous studies are focused on regional and sub-regional scales, this study contributes to deliver a climate information at a country level that is more relevant for decision making and for policy makers, and to document climate-related risks within a country to feed impact studies in key sectors of the development, such as agriculture and water resources.
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