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This study was to determine the hydrogeological and geoelectrical parameters affecting the productivity of water boreholes in the Daloa commune. Using the Schlumberger configuration, we carried out 15 parallel and perpendicular electrical profiling and 40 Vertical Electrical Soundings (VES). We also performed Electrical Resistivity Tomography (ERT) with a pole-dipole configuration at one site. The data processing allowed the identification of the different layers of the subsurface and their geoelectric properties that influence the productivity of the boreholes in the study area. These geoelectric data have shown that the productivity of the boreholes is more related to the conductive anomalies (W and U) than to the vertical electrical sounding. The processing of the hydrogeological data has shown that borehole productivity in the study area using Self-Organising Map (SOM) is a function of the hydraulic conductivity but also the thickness and density of the fracturing. Sixteen new boreholes on the main campus of Jean Lorougnon Guede University, Daloa, validate these results. The yield of these productive boreholes varies between 7.5 and 22 m3/h, with an average of 15.2 m3/h, four times higher than the values usually obtained in the study area. The success rate of these boreholes is about 70 %. This study has shown how effectively integrating hydrogeological and geoelectrical parameters provides information on the lithology and structural conditions in the subsurface necessary for productive drilling.

Study region: Lobo River Catchment (Côte d’Ivoire) Study focus: In this study, four regional climate models (RCMs) (RC4; CCLM4–8–17; RACMO22T and REMO) for the 2030 and 2050 periods compared to the reference period (1986–2005), combined with a simulation of land use and land cover (LULC) with Land Change Modeler, are used to drive the CEQUEAU model to quantify their impact on inflows to the Lobo River reservoir. 1988–2006 is used as a calibration period, whereas 2007–2015 is used for the validation. Three scenarios were used. First, varying LULC and keeping climate parameters static over the baseline period (scenario 1); in scenario 2, varying RCMs and keeping LULC static over the baseline period and in scenario 3, simultaneous variation of LULC and RCMs. New hydrological insights for the region: CEQUEAU showed good performance during calibration and validation: NSE (0.7, 0.75); R² (0.83, 0.65); PBIAS (14.1%, 12%) and RMSE (0.83, 2.15). The results show that a decrease in precipitation by 2030 (−14.6%), by 2050 (−15.2%) under scenario 2 (RCP 4.5 and 8.5) and by − 6.1% under RCP 4. 5 (Scenario 3), we observe an increase in runoff of 10.8–18.87% (Scenario 1), 1.2–4.46% (RCP4.5), 3.35% and 2.7% (RCP8.5) (Scenario 2) and 6.58–11.83 (RCP 4.5), 14.83–17.72% (RCP 8.5) (scenario 3). Changes in LULC were identified as the main causes, rather than climate variability.

Drinking water supply in the Lobo catchment is based mainly on surface water. In recent years, the adverse effects of climate change and strong population growth have led to increasing uncertainty about the availability of surface water and growing interest in groundwater in this region. Therefore, to ensure sustainable management of this resource, it is necessary to characterise and understand this groundwater system. This characterization requires knowledge of the geometry and structure of this aquifer system, which is a prerequisite for ensuring future water supply from groundwater resources. This aquifer system, which is the subject of this study, has never been the subject of a study aimed at characterising it and getting to know it better.This study aims to improve the knowledge of this aquifer system by elaborating the geometry of this aquifer system through the study of drilling data and electrical resistivity tomography (ERT). The results show that weathering of the granitic rocks in the Lobo catchment leads to the development of composite aquifers at two levels: a shallow saprolite aquifer overlies in places by a thick layer of ferruginous crust, and a deeper and very thick fractured aquifer. This shallow weathering aquifer, fed directly by precipitation, is tapped by conventional large diameter wells that are generally not immune to seasonal fluctuations. For sustainable management of this resource, an assessment of its recharge should be undertaken in addition to this study of the geometry of this aquifer system. The results of this study of the geometry of the Lobo catchment aquifer system improved the understanding of this aquifer system and will assist in groundwater exploration in this area.

Human activities and climate change are currently dominant processes that affect hydrological processes, resulting in alterations in water and sediment flows. Evaluation of the settling velocity of suspended solids is a critical parameter in modelling sediment transport. In this study, we investigated seasonal changes in suspended solids’ settling velocity and trapping capacity in the presence and absence of water turbulence on a dam reservoir. Using key parameters such as flow rate, mean settling velocity (V¯), critical velocity (vc), suspended solids concentration, ratio V¯/vc, and shape parameter ‘r’, the trapping capacity on the dam reservoir on the Lobo River in a tropical region was estimated. The results show that, considering the settling velocity of suspended solids, following the Gamma distribution law remains an innovative solution proposed to evaluate the trapping capacity in water reservoirs. The results show that the mean suspended solids settling velocity V¯ is well above the median rate V50%. For a parameter V¯/vc ≥ 4, there is an increase in the trapping capacity of the water retention. As established, a large proportion of the sediment is trapped. Furthermore, for a parameter V¯/vc ≤ 4, a decrease in the trapping capacity of the Lobo River water reservoir is observed.

Determination of groundwater recharge is a major challenge in areas where rainfall is generally abundant. Variability and uncertainty are inherent in the estimation of recharge, and several methods are therefore recommended for its estimation at a regional level. In this study, we evaluated several methods for estimating recharge: the web GIS-based automated hydrological analysis tool (WHAT), water table fluctuation (WTF), hydrograph analyses, a recession curve displacement method, graphical separation, and empirical formulas. The annual recharge estimated by combining direct recharge and base-flow varied from 84 mm in 2019 to 66.4 mm in 2020. The mean direct recharge was about 44 mm in 2018 and 57.3 mm in 2019, representing about 4% and 5% of the respective rainfall. In 2020, this direct recharge was 43 mm, or about 6% of rainfall, around 25% lower than in 2019. Base-flow separation methods and recession curve displacement generally gave low results, whereas modified empirical formulas gave results close to those of the WTF method and were considered more consistent and reasonable. The regression curve displacement method implemented in the United States geologic survey (USGS) RORA program was found to be unsuitable for the study area. However, the other methods presented more reasonable results and could be used to estimate groundwater recharge in the study area.

Agriculture is an axis of socio-economic development of the area of Denguele, Cote d'Ivoire. The evaluation of a project carried out as part of an agricultural campaign requires the handling of large amounts of heterogeneous data for effective monitoring. The design of an appropriate management tool is needed to organize and communicate information useful for decision making. The aim of this work is to provide a useful tool for a better management of information related to mechanical and motorized equipment used for rice cultivation capable to assure the food security in the application area. The solution involves the use of a geodatabase, which implicates the design and implementation of data in a relational database system. The data were modelled according to the Entity-Relationship formalism based on the MERISE method. The implementation of GIS under ArcGIS platform is used to display and map requests. The result of this work is a user-friendly interface that allows easy entry and querying the database for better decision making. This tool highlights the benefits of implementing a GIS application coupled with a relational database management system as part of a motorized agricultural campaign. [ABSTRACT FROM AUTHOR]

Te expansion of agro-industrial exploitations and the increased use of pesticides is a major concern for the quality of groundwater resources in the Abidjan area. The objective of this study is to assess the global vulnerability to pollution of these resources. Therefore, two methods based on the DRASTIC model were used. These methods are DRASTICLU and DRASTICLU-P in which land use is considered as a parameter, extending to 8 the number of analyze parameters in order to make the results more robust. To assess the significance of different parameters, a sensitivity test has been calculated. Validation of the results was made from the calculation of map error (Er) on the resulting maps, to see which is best suited for this study. The results show that the global vulnerability to pollution remains generally high in the area. These areas of high and very high vulnerability are found on almost all of the study areas, but with a strong presence in center and north. Together, high and very high vulnerability cover almost 84% of the study area. These areas are highly dependent on the recharge, aquifer media, soil media and the vadose zone. The calculation of uncertainties gave relatively high values due to high overall standard deviations. Calculated map errors are 22% and 21.5% respectively for DRASTICLU-P and DRASTICLU. Although these values are substantially equal, show that the DRASTICLU-P method remains the most suitable. [ABSTRACT FROM AUTHOR]

The present study was carried out to assess the quality and the suitability of the well waters for drinking in M'bahiakro city (centre-east of Côte d'Ivoire). The work was performed on 71 wells in February 2012 (dry season) and June 2012 (rainy season). Groundwater levels and physico-chemical parameters (pH, temperature, electrical conductivity, redox potential (Eh), Total Dissolved Solid (TDS) and Salinity) were measured to assess the water table fluctuation and the groundwater quality. Standardized Principal Component Analysis (SPCA) was calculated to group the well waters and to evaluate their suitability for drinking according to different classes. Water table varies between 125 and 135 m during the dry season and between 127 and 136 m during the rainy season with a West-Est flow direction. The recharge values ranged between 0.57 m and 5.57 m. Wells waters are generally acidic (pH<6.5), high mineralized with conductivities and Total Dissolved Solids (TDS) respectively above 600 μS/cm and 300 mg/l. Well water salinity values ranged between 0.30 and 0.5%. The Standardized Principal Component Analysis (SPCA) allowed distinguishing three important groups of water within M'bahiakro area: the first group of wells with high mineralized water, the second group of wells with high potential redox (Eh) and the third group of wells with pH closer to neutral. The first and second groups are not very suitable for drinking because they are suspected of being contaminated by anthropogenic sources such as septic tanks and wild dump. Waters of these wells need to be treated before any domestic use. [ABSTRACT FROM AUTHOR]