Water Geochemistry and Inorganic Quality: Case of the Lower Rusizi Plain Aquifer, North-Western Burundi

Abstract

The present study area is an alluvial plain consisting of fine clayey sand and coarse sand with mixed lithology. In September 2018, a water sampling campaign was carried out in 28 wells spread all over the plain. The interpretation of the results from the physicochemical analysis allows determination of the hydrogeochemical behaviour and quality of the groundwater sampled in this plain. The spatial distribution of physical and chemical parameters reveals a clear demarcation between the east and the west of the study area. Water samples from wells located in the western part of the plain show a high mineralisation with high electrical conductivity and total dissolved solids. Water samples from the southern and eastern parts show intermediate to low mineralisation. Graphical representations of chemical analysis in the Piper diagrams reveal that the groundwater in the study area can be classified into five families. The evaluation of water quality shows that concentration values of some ions like Na+, Ca2+, Mg2+, Cl−, HCO3− and SO42− are generally high in the western part of the plain along the Rusizi River with very high values particularly observed in the Rusizi delta.