Assessment of groundwater quality for irrigation suitability: a case study of Khana and Gokana LGAs, Rivers State, Nigeria

In this study, the quality of groundwater has been evaluated for irrigation in Khana and Gokana areas of Rivers State, Nigeria. Standard sampling and analytical methods were used. Chemical features were investigated via chemometric determinations, including major ions and potentially toxic elements (PTEs) and saturation index (SI) of selected mineral phases calculated using the PHREEQC software. Parameters like sodium adsorption ratio (SAR), sodium percentage (Na%), permeability index (PI), magnesium adsorption ratio (MAR), Kelly's ratio (KR), and Potential salinity (PS) were computed to ascertain its quality for irrigation purpose. Results revealed that the principal hydrochemical facies in the studied water samples is Ca-Mg-Cl. Geochemical model indicates the prevalence of dissolution process, since all carbonate and sulfate mineral phases are undersaturated. The occurrence of PTEs could be explained by the prevailing hydrogeochemical conditions and the dissolution/precipitation reactions of key mineral phases such as oxy-hydroxides. For the Khana and Gokana samples, respectively, SAR concentrations range from 0.19 to 0.71 and 0.22 to 0.80; MAR values range from 47.83 to 62.35% and 47.61 to 68.09%; KR ranges from 0.15 to 0.53 and 0.11 to 0.50; %Na ranges from 1.44 to 5.78 and 9.69 to 29.29; while PS are generally < 5. Most of the groundwaters fall into the C1-S1 and C2-S1 categories on the USSL diagram, with low-to-medium salinity hazard; while a few fall into the C3-S1 category. The deductions from the different indices computed in this study revealed that the groundwater is generally considered safe for irrigation purposes.