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International Journal of Agricultural Policy and Research Vol.8 (4), pp. 79-96, August 2020 Available online at https://www.journalissues.org/IJAPR/ https://doi.org/10.15739/IJAPR.20.009 Copyright © 2020 Author(s) retain the copyright of this article ISSN 2350-1561 Original Research Article Characterization of the hydrodynamics of an alluvial plain: The case of Karfiguela in Burkina Faso Received 15 April, 2020 Revised 6 July, 2020 Accepted 23 July, 2020 Published 18 August, 2020 Nestor Fiacre The study was carried out on the alluvial plain of Karfiguela, in the far south- COMPAORE1, west of Burkina Faso as part of the Support Program for Irrigation 1 Development (PADI). The current study made it possible to determine the Samuel NAKOLENDOUSSE *, hydrodynamic properties, the directions and directions of flow of the 1 Suzanne YAMEOGO Karfiguela alluvial plain aquifer.The hydraulic shock test method known as and the “slug test” was chosen for the determination of the hydraulic Sayoba KAFANDO1 conductivity, supported by two analysis methods: the Hvorslev method and the Bouwer and Rice method. The hydraulic conductivity values obtained 1Department of Earth Sciences, were compared, and subsequently, those obtained by the method of Bouwer Georessources Laboratory, and Rice were considered for interpretations. It can therefore be noted that University Joseph KI-ZERBO, the average conductivity values of the sites are between 6, 25.10-5 m.s-1 and Burkina Faso 3.81.10-6 m.s-1. The maximum value obtained is 4.31.10-4 m.s-1 and the minimum value is 9, 74.10-9 m.s-1. The analysis of the nature of the material *Corresponding Author Email: samples extracted from the micropiezometers shows a concordance with the [email protected] values obtained.In order to determine the directions and flow directions of the aquifer, monitoring of static levels were carried out from March 2013 to December 2016. This determination of directions and flow directions was made between March and April 2013 that is to say during the low water period (dry season). The static levels made it possible to calculate the piezometric levels thanks to the altitudes determined with Differential GPS (DGPS) surveys. The resulting piezometric surface shows a general flow that goes from the North to the Center and from the South to the Center. The piezometric maps show that the water table supplies the river in all the sites. Hence, zero flow limits and potential limits appear along the plain. Key words: Alluvial plain, hydraulic conductivity, flow directions (direction of flow), piezometric levels, Burkina Faso(West Africa) of Karfiguela (Banfora) INTRODUCTION Irrigated agriculture represents an essential alternative for rain-fed agriculture increasingly vulnerable because it is increasing agricultural production. Since the 1960s, the dependent on rainfall. world food situation has steadily improved, a performance According to Zella and Smadhi (2007), productivity of an made possible by the combined effects of various factors irrigated hectare is three times higher than that of a rain- including high-yielding seed varieties, irrigation, plant fed hectare. Irrigation therefore represents a key tool to nutrition and pests control irrigated agriculture occurs alleviate the ever-increasing food security needs in where other techniques such as rain-fed agriculture and developing countries. imports show their weaknesses. Climate change is making In Burkina Faso, over the past forty years, rainfall has Int. J. Agric. Pol. Res. 80 Figure 1 : Study site location map regularly decreased, with periods of increased drought, The innovative approach of this study is the use of surface especially in the 1980s. In addition, rainfall is often aquifers for irrigated agriculture with annually renewable unevenly distributed, from one year to another and even water resources. This approach has been tested in Brazil, during the same rainy season. Irrigation is therefore an (Burte, 2004) Niger (Yahaya et al., 2016) and more recently effective management tool against the climatic risks which in Algeria, Mebarek-Oudina (2017). weigh on agricultural production. Hence, the realization of hydrogeological studies that will In order to build the conditions for sustainable food make it possible to predict the quantitative and qualitative security by 2030 and to contribute structurally to reducing impact of the practice of irrigated agriculture on the social inequalities and poverty, the National Food Security aquifer. This study will focus more explicitly on the Strategy (NFSS), in line with the Poverty Reduction Strategy hydrodynamic characterization of the alluvial plain aquifer. Paper (PRSP) and the Sustainable Development Objectives This involves the determination of the aquifer's (SDO), has set the objective of making irrigation play a hydrodynamic parameters, piezometrics and water flow significant role in increasing and securing agricultural directions and its periodic renewal. production; increasing value added, improving employment To achieve these objectives, we will use the structures set and incomes in rural areas and preserving natural up by the project, namely a network of forty-nine (49) resources and productive capital. micro piezometers. The main activities aim at determining For this reason, the PADI-BF 101 project, in its activities, the hydrodynamic parameters which will be done by in situ aims at studying the aquifer of the alluvial plain of hydraulic shock tests known as “slug-test”. The Karfiguela. It could represent a potential source of determination of the piezometric levels using piezometric groundwater that can be used as an alternative water probes and various other types of probes will make it resource for the producers located there. The alluvial plain possible to determine the piezometry of the plain and to can represent a significant supply capacity for irrigated deduce the flow directions. areas, but sustainable management environment friendly management is essential. This must result in an extraction Study zone which must not be beyond the aquifer capacity and also keeping in mind the need of protecting the resource. Taking The alluvial plain of Karfiguela is located in the Cascades into account the needs of other sectors related to the use of region, province of Comoé, and commune of Banfora with this groundwater as well as the long-term survival of an overflow in the northern part, in the commune of ecosystems is also paramount. In this case, it is necessary to Bérégadougou (Figure 1). determine the origin and the dynamics of groundwater The plain is located between longitudes 4° 50 ’and 4 °42’ flows. West and latitudes 10 ° 44 ’and 10 ° 28 ° North, it covers an Compaore et al. 81 Figure 2: Geological formations of the alluvial plain of Karfiguela Sources: VREO, 2006 area of 46 km² and extends over 28 km long. arkosics and stones, fine quartzite sandstone, pink sandstone with shale flow. Geology . A formation made by shales and volcano- sediments; globally, they are pelites, sandstone shales, The alluvial plain of Karfiguéla is made of the following lustrous gray-black shales, tuffaceous shales as well as rare geological formations: (Figure 2). quartzitic horizons. (Ouédraogo, 2006). A tonalitic ensemble consisting of granodiorite, tonalite and quartz diorite. This ensemble would have been Hydrogeology in place from 2210 million years to 2100 million years in a quasi-continuous manner (Ouédraogo, 2006); The Cascades region is defined by two hydrogeological . The formation of Kawara-Sindou Sandstones (GKS) entities: formed by conglomerate coarse sands, with a thickness varying from 60 to 350 meters. It lies in discordance on the Sedimentary areas lower sandstones. The Formation of lower sandstones with The sedimentary zone consists of a thick series of rocks thicknesses varying from 50 to 300 meters. The following containing several aquifer levels. This is essentially a succession can be seen from top to bottom: fine red sandstone sedimentary basin of very old age. Int. J. Agric. Pol. Res. 82 Figure 3: Distribution of micropiezometers in the plain Certain aquifer levels provide very significant flows of the probes, baro diver probes, a bailer, a differential GPS, and order of several tens of cubic meters per hour. computer equipment Basement areas Data acquisition methodology The crystalline basement area is predominantly granitic The studies to be carried out are made thanks to the works with shales, green rocks and dolerites. The exploitable installed on the plain. It is a network of forty-nine (49) flows are modest. The water resources are either in the micropiezometers which are distributed by independent altered zone and more or less loosened for granitic rocks groups (Figure 3). (arenas), or in the fractured rock. In order to ease representation, it was decided to separate the micropiezometers into five groups based on the locality. Hence we have: North Banfora, Karfiguela, MATERIALS AND METHODS Siniena, Tengrela and Diarabakoko(Table 1). Carrying out this study required appropriate equipment Determination of hydrodynamic parameters and a strict methodology in various fields (hydrodynamic parameters, piezometries). We will present in this part, the Determining the hydrodynamic parameters was a crucial material as well as the methods used. step in the characterization of the aquifer. There are several methods for determining hydrodynamic parameters such Materials as pumping tests or groundwater tests, in-situ permeability tests, laboratory permeability tests

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