Assessment of water resources quality for multiple purposes in parts of the Volta basin in northern Togo, using chemometric-based indices

Abstract

Water quality assessment is essential for its sustainable use. Therefore, this study evaluates the quality of water resources in the Togolese portion of the Volta Basin by combining physicochemical analyses, chemometric indices, and multivariate statistical methods. A total of 115 samples from surface water, groundwater, and tap water were collected during the dry season and at the end of the rainy season. Selected hydrochemical parameters have been determined using standard methods. The Water Quality Index (WQI) and conventional hydrogeochemical approaches have been applied to examine the health of groundwater resources and the controlling drivers. The results revealed that surface waters experience low mineralization during the wet season, whereas groundwater shows increased mineralization associated with infiltration and mineral dissolution. The Water Quality Index shows that only tap water maintains consistently potable quality, unlike surface water and groundwater, whose quality was unsuitable at 70% and 21%, respectively, during the rainy season, against 47% and 10% in the dry season. Principal Component Analysis reveals three major gradients controlling water quality: natural silicate and accessory minerals weathering, nitrogen-based anthropogenic inputs, and metal contamination. Bivariate analysis indicates that mineralization is mainly controlled by silicate weathering, carbonate dissolution, and ion exchange processes, while the low concentrations of Cl⁻ and SO₄²⁻ rule out any significant evaporitic influence. Irrigation indices indicate that most waters are dominated by sodium and magnesium. Industrial stability indices highlight varying corrosion and scaling risks by site and season. These findings provide essential insights for the sustainable and integrated management of water resources in the Volta Basin.