HYDROCHEMICAL APPRAISAL OF GROUNDWATER RESOURCES IN PART OF SOUTHERN ANAMBRA BASIN:

ITS IMPLICATIONS FOR IRRIGATION PURPOSE

Abstract

Irrigation is vital for food security, but climate change and pollution threaten it. Thus, regular evaluations of groundwater quality for irrigation are needed. This study collected and analyzed thirty-five (35) groundwater samples from boreholes in the Southern Anambra Basin, covering the Ameki and Ogwashi-Asaba Formations. Six irrigation quality indices: Kelly’s Ratio (KR), Sodium Adsorption Ratio (SAR), Soluble Sodium Percentage (SSP), Residual Sodium Carbonate (RSC), Magnesium Adsorption Ratio (MAR), and Permeability Index (PI), were calculated to evaluate the area’s irrigation suitability. Doneen PI, USSL, and Wilcox diagrams were also employed in evaluating irrigation suitability. The pH, EC, and TDS of the groundwater samples ranged from 6.6 to 8.4, 13 to 889µS/cm, and 15.6 to 557.9mg/L, respectively. The concentrations of HCO₃^-, SO₄^2-, Cl^-, Ca²⁺, Mg²⁺, Na⁺, and K⁺ ranged from 24 to 580, 1 to 20, 0.4 to 92.5, 10 to 74, 0.09 to 49.50, 2.26 to 30, and 0.67 to 10.0 mg/L, respectively. In general, the physicochemical parameters met the WHO and NSDWQ guidelines for drinking waters. The range of KR, SAR, SSP, RSC, MAR, and PI were 0.019-1.712mmol/L, 0.067-2.113, 1.86-63.13%, -5.36-7.80mmol/L, 0.00-3.79, and 15.82-547.10%, respectively. All samples had suitable SAR and MAR values for irrigation, while 97.14%, 94.29%, 80%, and 77.14% had suitable SSP, KR, RSC, and PI, respectively. This study has demonstrated that groundwater within the study area is suitable for drinking and irrigation, however, it is essential for periodic assessment as anthropogenic activities continue to increase in the area.