Hydrochemical Evolution of Water in the Crystalline Basement Aquifer in the Pra Basin (Ghana): Field Observations and Geochemical Modelling
Abstract
The Pra Basin in Ghana is well-known for its abundant mineral resources, dense
forest coverage, and fertile soil. The region faces major water management challenges
due to illegal mining practices, resulting in surface water pollution and necessitating
groundwater use as an alternate water source. Unfortunately, there is limited
information available regarding the chemical characteristics of groundwater in the
region, posing challenges for water management. This study examined the quality,
hydrochemical variability and geochemical processes driving the chemical evolution
of the groundwater. Samples of surface water and groundwater were collected and
analyzed for chemical parameters. We employed multivariate statistics, including
cluster and factor analysis, to identify regional variations and interrelationships
among the parameters. The resulting clusters were used to formulate a hypothetical
groundwater flow path to model the geochemical reactions that control the
groundwater composition using combinatorial inverse modelling based on the local
thermodynamic equilibrium hypothesis. The weathering of silicate minerals,
including albite, anorthite, chalcedony, and k-feldspar, was found to be the dominant
process driving the groundwater's chemical evolution. Models adequately predicted
the composition of groundwater along the flow path and serve as a guide for the
development of sustainable water resource management strategies for the catchment.
Overall, our modelling approach presented here can be useful in regions with large
variability in water chemistry and limited knowledge of aquifer mineralogy.
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