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Application of geochemical and stable isotopic tracers to investigate groundwater salinity in the Ochi-Narkwa Basin, Ghana

Author:
Ganyaglo, Samuel Y., Osae, Shiloh, Akiti, Tetteh, Armah, Thomas, Gourcy, Laurence, Vitvar, Tomas, Ito, Mari, Otoo, Isaac A.
Source:
Hydrological sciences journal 2017 v.62 no.8 pp. 1301-1316
ISSN:
2150-3435
Subject:
basins, chlorides, coasts, deuterium, geochemistry, groundwater, groundwater flow, ions, isotope labeling, mixing, models, oxygen, rain, saltwater intrusion, silicates, soil water, stable isotopes, water salinity, water salinization, weathering, Ghana
Abstract:
Rainwater, groundwater and soil-water samples were analysed to assess groundwater geochemistry and the origin of salinity in the Ochi-Narkwa basin of the Central Region of Ghana. The samples were measured for major ions and stable isotopes (δ ¹⁸O, δ ²H and δ ¹³C). The Cl ⁻ content in rainwater decreased with distance from the coast. The major hydrochemical facies were Na-Cl for the shallow groundwaters and Ca-Mg-HCO ₃, Na-Cl and Ca-Mg-Cl-SO ₄ for the deep groundwaters. Groundwater salinization is caused largely by halite dissolution and to a minor extent by silicate weathering and seawater intrusion. Stable isotope composition of the groundwaters followed a slope of 3.44, suggesting a mixing line. Chloride profiles in the soil zone revealed the existence of salt crusts, which support halite dissolution in the study area. A conceptual flow model developed to explain the mechanism of salinization showed principal groundwater flow in the NW–SE direction.
Agid:
5736874