Détermination des zones potentiellement favorables à l’implantation de forages manuels à partir d’analyse multicritère et d’un SIG : cas de la Côte d’Ivoire

Abstract

Cette étude a été effectuée dans le cadre d’un projet initié par le Fonds des Nations Unies pour l’Enfance (UNICEF). En effet, pour faire face aux besoins toujours croissants en ouvrages d’alimentation en eau potable, des solutions adaptées doivent être envisagées. Parmi celles-ci, la réalisation de forages peu profonds (moins de 40 m) s’avère être l’une des solutions pour satisfaire les besoins en eau de certaines localités de la Côte d’Ivoire. Cette étude a donc été entreprise dans le but de localiser des zones où l’implantation de forages manuels est favorable. Elle a été réalisée à partir de la collecte de données géologiques, hydrogéologiques, géomorphologiques et de données relatives aux points d’eau existants. L’intégration de toutes ces données dans un Système d’Information Géographique (SIG) a permis l’élaboration d’une carte de zones favorables à l’exploitation des eaux souterraines à travers des puits peu profonds. Elles correspondent à de larges zones de substrat cristallin couvert d’une zone d’altération argilo-sableuse d’épaisseur significative (20–30 m), facteur particulièrement favorable aux perforations manuelles. On relève aussi un niveau partiellement favorable, qui devient favorable ou très favorable dans les vallées fluviales à faible pente (< 3 °). Les secteurs les moins favorables se situent dans les zones nord-orientales, sud-occidentales et dans la zone montagneuse de Man. Il est aussi important de considérer que les zones de bas-fonds présentent potentiellement des conditions plus favorables, mais nous constatons que la population est plus concentrée dans des zones élevées à cause du risque d’inondation et de conditions défavorables du terrain liées à la présence d’eau stagnante dans les zones les plus basses.This study was carried out within the framework of a project introduced by the United Nations Children's Fund (UNICEF). Indeed, in order to respond to the increasing needs for boreholes for drinking water supply, adapted solutions must be envisaged. Among these, the realization of shallow boreholes (less than 40 m) turns out to be one of the possible solutions to satisfy the water requirements of certain localities of the Ivory Coast. This study was thus undertaken with the aim of locating zones where the presence of manual boreholes would be favorable. The study used geological, hydrogeological and geomorphological data and data relative to existing water sources. The integration of all these data in a Geographic Information System (GIS) allowed the elaboration of a map of zones favorable for the supply of groundwater through shallow wells. They correspond to wide zones of crystalline substratum covered by a weathered zone of sandy-clays of significant thickness (20–30 m), a factor that is particularly favorable for manual boreholes. We also identified a partially favorable level, which becomes favorable or very favorable in the river valleys with low slope (< 3 °). The least favorable sectors are situated in the northeastern and southwestern zones and in the mountainous zone of Ma...

Using GIS and Multicriteria Analysis to Map Flood Risk Areas of the Tongo Bassa River Basin (Douala, Cameroon)

“…The identification of the criteria is a decisive and delicate phase that conditions the quality of the data generated with a view to their inclusion in the model. Thus, after reviewing the literature, prospecting the watershed, regarding the work of Jourda et al . (2006), Mahmoud and Gan (2018), Phonphoton and Pharino (2019), and Youan et al .…”

“…The identification of the criteria is a decisive and delicate phase that conditions the quality of the data generated with a view to their inclusion in the model. Thus, after reviewing the literature, prospecting the watershed, regarding the work of Jourda et al (2006), Mahmoud and Gan (2018), Phonphoton andPharino (2019), andYouan et al (2011) and available data, four criteria were analyzed to meet the objective. The defined criteria were elevation, drainage density, distance to watercourses, and land use.…”

Contribution of gravity data and Sentinel-1 image for structural mapping. Case of Beni Mellal Atlas and Beni Moussa plain (Morocco).

“…In this study, the manual extraction by visual interpretation was adopted for the lineaments identification in the study area [18,68,69,70,71,72,73]. Those lineaments are materialized by the limits formed by the dark and clear zones lines [74][75] more or less regularized and the hydrographic network disturbances [76].Their signature in the field is very diverse, they may correspond to contacts between formations of different lithology, outcrop limits or to fractures or faults lines [77][78].…”

“…The two directions NW-SE and NE-SW guide in surface the majority of hydrographic network as well as the main springs distribution which emerge from the northern atlasic border of Tadla plain. Indeed, had demonstrated the influence of the brittle tectonic on the drainage network organization and the spring resurgence because it accelerates the erosion and alteration processes and therefore the rivers development For a better results analyzing and in order to rule on strucural origin [70][71][72][73][74][75][76][77][78][79][80][81][82][83][84][85][86] of deduced lineaments from gravity data and radar images combination, we proceeded with a breakdown of the study area into tectonic sectors. Gravimetric lineaments and the ones deduced from the Sentinel-1image were correlated and compared for different parts of the study area ( Figu.13).…”

Groundwater Potential Assessment in the Rural Loulouni Municipality (Southern Mali): Decision Tree Approach

“…The potentiality map by decision tree classification was validated with borehole flow data using the sensitivity trend curves proposed by Jourda [6], and Jourda et al [13] (Fig. 4).…”