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Le territoire burkinabè est constitué à plus de 80% de formations de socle. Ces formations renferment des ressources en eau souterraine qui constitue la seule source en eau potable de certaines populations. Cependant, le quart des forages réalisés en vue d’exploiter ces eaux sont négatifs. Une bonne compréhension du fonctionnement hydrogéologique e...
Contexts in source publication
Context 1
... sont six essais de longues durées qui ont été réalisés dans les forages S1CN, S5, S10, S12, S15 et SaG, (Figure IV.2 ...
Context 2
... le premier pulse, il convient de noter que l'amplitude du bruit est supérieure à celle du signal ( Figure IV. Par ailleurs, nous constatons que la profondeur du niveau statique est surestimée par la RMP de 2,7 m et celle du substratum est surestimée de 11,1 m ( Figure IV.25). imprécision ne peut pas être déterminée pour S16 parce que ce piézomètre était obstrué lors de la réalisation du sondage. ...
Citations
... Water is an essential element, even primordial to life on earth. The history of water and that of men are closely linked [1]. Just like air, drinking water is vital; having it in sufficient quantity and quality contributes to maintaining health and directly contributes to the quality of the environment [2]. ...
... The calculation of the ionic balance (IB) is done by checking the scale of anions and cations. In theory, the sum of anions expressed in meq/L must correspond exactly to the sum of cations also expressed in meq/L [1]. A perfectly balanced ionic balance is rarely obtained. ...
... In this sense, the alterite aquifer is defined as heterogeneous, as it is a complex structure due to the presence of discontinuities [32][33][34][35]. In fact, the flow exists on the basis of the presence of fractures in these media dividing the space into a series of permeable masses, known as porous matrices [36,37]. The existing watercourse interacts through the exchange of flows. ...
... The calibration procedure consists in reducing the bias between the observed and simulated values through the adjustment of model parameters, here the hydraulic conductivity and groundwater recharge [36,38,[46][47][48]. In this study, a "trial and error" procedure is used, in which values are manually assigned to the various parameters to achieve an optimal calibration. ...
... This refers first of all to the quantification of the pollutant and its progression from the surface to underground percolation. In this work the steady state hydrodynamic model is defined and coupled to the transport model [36,52]. The preservation of the resource requires a good understanding of the processes of transfer or transport of pollutants. ...
In Burkina Faso, human activities around water points in rural areas affect groundwater resources, which become unfit for consumption. Nearly 33.5% of boreholes are subject to point source pollution. The assessment of the evolution of such pollution should be monitored to assess groundwater quality. In addition, withdrawals for irrigation alone are estimated at 85%, i.e. 46% of the water demand, heightening the deterioration in quality while creating depression zones further leading to an increase in recharge. It is therefore critical to understand the evolution and fate of the transfer of pollutants in such environments. In this study, we aimed to model the transfer of pollutant and predict the future state of pollution using the MT3D-USGS Groundwater Solute Transport Simulator code through the Groundwater Modelling Software (GMS) over the period 2012-2062 (50 years). A mathematical model is further developed through inferential statistics and used as a surrogate model for comparison. The results showed that deterioration in water quality was more attributable to withdrawals, especially for Cyanide (Cn) and Arsenic (As). A rather slow degradation is reported for Lead (Pb), which extends over 22 km, and Fluoride (F), which extends from 4 to 10 km due to localized recharge. A faster degradation for Cn over a distance of 2 to 16 km and as from 3 to 11 km is also observed because of the geological setting of the subsoil. These results might assist decision-makers for the quantitative and qualitative management of groundwater resources, and the management of the basement aquifer in the area through the establishment of protection zones.
... To this we can add that the method used as the Schlumberger can lead to discrepancies. Indeed, this is confirmed by the results of the synthetic modeling which concludes that the Wenner device is more suitable and produces less deviation [16]. However, it has limitations in estimating the depth of fissured zones and its implementation. ...
... The section of electrical resistivity makes it possible to perceive a very resistant environment characterized by electrical resistivities greater than 400 ohm.m, in line with the presence of laterite from the surface. In the geological context of crystalline basement, beyond 400 ohm.m, we have to deal with the presence of massive rocks of relatively low porosity and whose alteration is not deep [19][20]. At the east of this profile, however, there are formations of lower resistivity below 400 ohm.m which are more characteristic of alterites. ...
... The application of Electrical Resistivity Tomography in Burkina Faso has already proven itself in the sense that it made it possible to image geological formations and to explain the behavior of aquifers in a crystalline basement environment [21][22][23]. The combination of the Wenner α and Wenner β devices for electrodes spaced 5 m apart and used by Soro [19]; Outoumbe has allowed to observe the presence of discontinuities over an investigation depth of 60 m, and to well describe the alteration profile of hard rock aquifers [22]. Geological conceptual models have been proposed on this basis facilitating the comprehension of such media. ...
... The ratio of outliers after data processing is less than 1% for all electrical resistivity sections: the data can be considered good at the end of this step. Furthermore, the RMS values obtained ranging from 1.83% to 4.37% are low compared to those obtained by Soro [19] which vary between 4.8% and 13.2%. Such values attest the quality of the models obtained. ...
Throughout Burkina Faso's road network, some roadways have experienced subsidence or collapse following pipe ramming works conducted for the laying of pipes such as drinking water supply networks. When such works are conducted, it is difficult to make a diagnosis of the properties of the formations underlying the road embankment because a destructive sounding would lead to expensive and tedious repairs. In this present study, a geophysical method, namely electrical resistivity tomography has been used to image the structure and the geometry of these formations so as to anticipate potential disasters. Four electrical resistivity profiles were conducted near the insertion and receiving pits, parallel to the national road N°4, at the exit of the capital Ouagadougou. The strategy of prospection has allowed to image down to an investigation depth of approximately 10 m. The study showed that at an average depth of 2 m, an environment of very low electrical resistivity (about 50 ohm.m) is observed in a very resistant environment. This conductive environment corresponds to the presence of a porous and very wet material which extends laterally and in depth under the roadway, and which can lead to a subsidence or a collapse of this roadway on the surface. ARTICLE HISTORY
... The thicknesses of the alterites are relatively significantly thicker in the central valley (30 to 50 m) and progressively decrease towards the catchment ridges [45]. [48] and Soro et al. [39]). S1CN, S1CNP, S1, S2, S11, and SaG are observation wells. ...
... The Sanon experimental site is equipped with 16 functional observation wells (Figure 1d), 7 of which (S1CNP, S2, S2BIS, S3, SA, S18, S19) capture only the saprolite (shallow reservoirs), 5 (S1CN, S1, S5, S11, S11P) capture only the fractured layers (deep reservoirs), and 4 (S1Bis, S8, S16, SaG) both reservoirs. The [48] and Soro et al. [39]). S1CN, S1CNP, S1, S2, S11, and SaG are observation wells. ...
... Over the CM and CG plots, the cultivation practices are flat plowing perpendicular to the slope (to retain surface runoff). Such practice is predominant in the entire watershed [48]. The observed differences could be due to both the effect of land use and location on the hydrographic network. ...
Groundwater is a vital water supply for local populations and ecosystems globally. With the continuous population growth, the anthropic pressure on groundwater is ever increasing, thus reducing the amount of available water resource. Yet, estimating the impact of anthropogenic activities on aquifer recharge is still a significant challenge for research, especially in basement aquifers. This study aims to improve the actual knowledge of deep drainage and deep aquifer recharge pathways and dynamics in the basement as affected by land use/land cover (LULC). The methodology used in this study accounted for hydraulic processes in soil layers within both unsaturated and saturated zones in an integrated approach. An experimental setup consisting of three (3) experimental plots, respectively under natural vegetation (NV), cropped millet (CM) and cropped groundnut (CG) on which deep drainage was monitored during the years 2020 and 2021. The results show significant differences between the LULC types after two years of implementation. Deep drainage is improved under CM and CG plots located in the central valley, as compared to the NV plot located in the ridge zone. Deep drainage is estimated at 8%, 24% and 25% of the annual rainfall, respectively for NV, CM and CG. The ratio between the recharge value obtained by the water table fluctuation (WTF) method and the deep drainage tends to 1 for the CM and CG plots, highlighting a rapid water transfer between unsaturated and saturated zones. The central valley, which seems to be a preferential recharge pathway, provides promising insights under specific conditions for the implementation of artificial recharge infrastructures.
... According to [20], in practice, the choice of geophysical methods depends on: ...
... In the context of groundwater research, the parameters sought concern the reservoir: its position, its geometry and the quality of the water it contains [20]. ...
in English
Clean drinking water supply is a major concern to the population of the urban municipality of Boké, Republic of Guinea. This study is aimed to investigate the favourable geological structure for the accumulation of groundwater in Boké. Apparent resistivity data was collected by using the Schlumberger-type vertical electrical sounding technique. The apparent resistivity values were obtained on a bi-logarithmic scale in which the distances AB/2 were plotted on the abscissa and the resistivities are on the ordinate. It found the number of terrains and their characteristics (resistivity and thickness) in the area and the behaviour of the current in the soil through a curve. The results show that the structures favourable to the accumulation of groundwater were fractured dolerites, cracked shales and cracked or crushed sandstones. The sandstones were the most important in terms of the amount of water. They are located at a depth of more than 100 metres. It was also found that dolerites and shales are located at shallower depths (less than 100 m).
... La forte sollicitation de cette ressource est aussi due au fait qu'elle est généralement de bonne qualité, moins sensible à la variabilité climatique et souvent abondante en zone sahélienne (Yonas et Tesfa, 2021 ;Viguier, 2016 ;Affoué et al., 2016). En général, les eaux souterraines contenues dans les aquifères se rechargent soit directement à partir de la pluie, soit indirectement à partir de la percolation latérale à travers le lit des cours d'eau, et/ou de façon localisée à partir des surfaces d'accumulation (Soro, 2017 ;Leduc, 2003 ;Lerner et al, 1990). Cette recharge qui constitue un élément essentiel dans le cycle hydrologique se fait préférentiellement dans des zones potentielles (Ibrahim et Moussa, 2020). ...
La présente étude a été effectuée pour déterminer les zones potentielles de recharge des eaux souterraines. Pour ce faire, la démarche méthodologique était basée sur l’analyse multicritère associée aux techniques géospatiales. Les données utilisées étaient entre autres les images satellitaires, les fonds cartographiques, les données pluviométriques et les niveaux statiques. Ces données ont permis d’exprimer sous forme de carte thématique les facteurs régissant la recharge (pente, drainage, lithologie, fracturation, sol, pluviométrie et occupation du sol). L’analyse de sensibilité par suppression d’un paramètre a permis d’établir l’ordre d’influence suivant : Lit > Sol > AACH > Df > Pl > Pe > Dd > OS. Le croisement de tous ces paramètres après pondération a conduit à l’élaboration de la carte qui montre que les zones à ort potentiel occupent 3 % de la zone d’étude pendant que les zones de faible à faible potentialité sont de l’ordre de 58 % dans le bassin. Les zones à potentialité moyenne quant à elles représentent 39%. Ce support cartographique constitue indéniablement un outil d’aide à la décision pour les gestionnaires de l’eau. This study was carried out to determine potential groundwater recharge areas. To do this, the methodological approach was based on multi-criteria analysis associated with geospatial techniques. The data used were, among others, satellite images, base maps, rainfall data and static levels. These data made it possible to express in the form of a thematic map the factors governing the recharge (slope, drainage, lithology, fracturing, soil, rainfall and land use). The sensitivity analysis by deletion of a parameter made it possible to establish the following order of influence: Lit > Sol > AACH > Df > Pl > Pe > Dd > OS. The crossing of all these parameters after weighting led to the development of the map of potential recharge zones which revealed that the zones with high potential occupy 3% of the study zone while the zones with low to low potentiality are around 58% in the basin. Areas with average potential represent 39%. This cartographic support is undeniably a decision-making tool for water managers.
... Compared to neighboring sedimentary aquifers, the conceptualization of the recharge pathways at local and regional scales in the weathered rock aquifer of the Sahel is more challenging as these aquifers are discontinuous and heterogeneous. From recent results, a typical weathering profile of weathered rock aquifer in the Sahel and other tropical regions is composed of the fissured or fractured horizon overlain by a clayey saprolite layer (Dewandel et al. 2006;Lachassagne et al. 2014Lachassagne et al. , 2021Soro 2017). The saprolite is often overlain by a laterite layer with variable hydraulic conductivity ranging from 10 -7 to 4 × 10 -3 m/s (Bonsor et al. 2014). ...
Groundwater recharge rate for weathered rock aquifers in the Sahel of West Africa is sparse due to insufficient knowledge of the recharge pathways. This study was initiated in the Tougou ephemeral river catchment (37 km2) to improve understanding of recharge pathways to a weathered rock aquifer in the dryland of Burkina Faso. It is based on field investigations conducted in 2016–2020 on a piezometric transect and large-diameter wells, perpendicular and longitudinal to the river, respectively. Geophysical measurements, lithologs analysis, permeability tests, groundwater and river level monitoring, and rainfall measurements were undertaken. The results showed a laterally continuous saprolite aquifer (10–22 m thick) overlain by residual soils beneath the river and discontinuous laterite on the banks. Below the river, the saprolite overlays the weathered schist aquifer with an upward or downward hydraulic gradient regardless of the seasons. The saprolite is replenished by focused recharge from the river and diffuse recharge from the rainfall on the banks, according to information from the groundwater hydrographs, groundwater tracing results, and cross-correlation between the groundwater levels and the two potential recharge sources (rainfall and river water). The low hydraulic conductivity, electrical resistivity tomography profiles and lithologs indicate restriction of diffuse and focused recharge through soil matrix infiltration, suggesting there are preferential recharge pathways. For the 2018–2020 period, the water-table fluctuation method provides recharge estimates of 14–51 mm/year on the northern bank, 10–36 mm/year on the southern bank and 148–194 mm/year in the riverbed.
... Regarding the Burkina Faso basement complex, studies related to the characterization of groundwater recharge mechanism are almost nonexistent. A handful of previous attempts have mainly focused on quantifying groundwater recharge [7,[35][36][37]. However, most of these studies did not consider the pathways followed by the water throughout the soil layers to the aquifer, which might lead to uncertainties in the amount of recharge estimates [17,31,32]. ...
... Attempts to quantify the recharge have estimated it at a maximum of 10% of the rainfall [48,50]. [37,56]). S1CN, S1CNP, S1, S2, S11, and SaG are observation wells. ...
... The Sanon experimental site is equipped with 16 functional observation wells ( Figure 1a), seven of which (S1CNP, S2, S2BIS, S3, SA, S18, and S19) capture only the alterites (shallow reservoirs), whereas five (S1CN, S1, S5, S11, and S11P) capture only the fractured layers (deep reservoirs), and four (S1Bis, S8, S16, SaG) capture both reservoirs. The objective of having well observations that capture only shallow weathering aquifers, fractured aquifers, or both is to understand the hydrodynamic and geochemical processes that take Figure 2. The 2D geological model and associated electrical resistivity values (adapted from [37,56]). S1CN, S1CNP, S1, S2, S11, and SaG are observation wells. ...
In Burkina Faso, the basement aquifers represent a major asset in terms of quantity and quality, for both drinking and irrigation purposes for rural populations. They provide water resources that can guarantee the long-term needs of the populations, provided that a sustainable management policy for these resources is adopted. Yet, any groundwater resource management policy is necessarily linked to a better knowledge of aquifer recharge mechanisms, which is yet to be fully assessed in the Sahelian basement area. The objective of this study was to characterize the recharge mechanism within the experimental site of Sanon, located in the basement zone in Burkina Faso, using a coupling of hydrodynamic and chemical approaches. The hydrodynamic approach consisted of monitoring the spatial and temporal distribution of the piezometric levels of the aquifers along a north–south and east–west transect and determining soil infiltration capacity. The hydrochemical characterization of the aquifers was carried out through an analysis of groundwater samples from the concerned aquifers and daily tracing of the electrical conductivity of the aquifer water. The cross-analysis from the results of the implemented approaches shows a direct recharge mechanism through rainwater infiltration in the central valley, an indirect recharge mechanism in the lowlands, and a recharge mechanism by lateral transfers in the peripheral aquifers of the Sanon experimental catchment. The existence of a piezometric dome reveals in the central valley a zone of preferential recharge and water movement. The water of the central valley is the least mineralized with electrical conductivities below 100 µS/cm. This mineralization follows the direction of the water flow.
... Crystalline basement regions are known for their structural complexity. The associated water resources reflect this complexity: highly heterogeneous, constraining identifier and to be characterized [4]. ...
... It is therefore necessary to use complementary methods, in particular nondestructive geophysical methods [4]. The combination of these geophysical and hydrogeological methods could help to gain a deeper understanding of the productivity of water drilling in basement environments. ...
