Author(s)

Wèré Gédéon Sambiénou^1*, Laurence Gourcy², Abdoukarim Alassane¹, Christophe Kaki³, Yao Yelidji Joël Tossou⁴, Daouda Mama¹, Moussa Boukari¹, Kamel Zouari⁵

¹Laboratory of Applied Hydrology, University of Abomey-Calavi, Cotonou, Benin.
²BRGM, Orleans, France.
³Department of Science and Earth, University of Abomey-Calavi, Cotonou, Benin.
⁴Directorate of Water Resources (DGEau), Cotonou, Benin.
⁵Laboratory of Radio-Analyses and Environment, National Engineering School of Sfax, Sfax, Tunisia.

The knowledge about groundwater flow conditions within Volta river basin in Benin, has restricted information coming to piezometry, water storage time, water path, and water quality. A good groundwater resources assessment of this sudano-sahelian area, is a huge condition for the sustainable management of water resources, which since the part of the 20th century is facing a severe drought that leads to a greater aridity. This article provides a summary with the main elements of carbon isotope (¹³C and ¹⁴C) as well as tritium (³H) coupled with hydrogeological and hydrochemical data. The goal is to improve the initial water recharging and the groundwater flow system within the aquifer. Two main results can be produced from the groundwater chemistry. First, the interactions between groundwater and clay minerals related to the residence time of groundwater are indicated by a slight evolution of Ca-HCO₃ and Ca-Mg-HCO₃ to Na-HCO₃. Beside that towards water types Cl-NO₃ indicates the anthropogenic influence on groundwater, related to agricultural activities and sanitation conditions. The carbon-14 activity measured on the TDIC is between 17.29 and 85.47 pmC. Therefore, it contains some samples covering a wide period of time from now to the Holocene implying a continuous system recharging over time. All the data confirm the assumption of a homogeneous, largely unified aquifer system with a multi-layer structure, but it also points out the low resource sustainability and a strong anthropogenic contamination of the most superficial horizons.

Hydrochemistry, Radiocarbon, Recharging, Residence Time, Dating, Volta River Basin in Benin

Sambiénou, W. , Gourcy, L. , Alassane, A. , Kaki, C. , Tossou, Y. , Mama, D. , Boukari, M. and Zouari, K. (2018) Flow Pattern and Residence Time of Groundwater within Volta River Basin in Benin (Northwestern Benin). Journal of Water Resource and Protection, 10, 663-680. doi: 10.4236/jwarp.2018.107038.