Seasonal hydrochemical characterization and irrigation suitability of groundwater in selected towns of Awka south local government area, Nigeria

Abstract

Groundwater is a vital resource for domestic, agricultural, and industrial use, particularly in developing regions where access to safe surface water is limited. This study assessed the physicochemical characteristics and irrigation suitability of groundwater in selected towns (Awka, Nibo, Amawbia, and Nise) within Awka South Local Government Area, Anambra State, Nigeria. Groundwater samples were collected from boreholes during the dry (October–December 2024) and rainy (April–May 2025) seasons and analyzed using standard laboratory procedures. Key parameters evaluated included pH, total dissolved solids (TDS), total hardness (TH), major cations and anions, and heavy metals. To determine water suitability for irrigation, several indices were computed, including the Water Quality Index (WQI), Sodium Adsorption Ratio (SAR), Permeability Index (PI), Magnesium Hazard (MH), Kelly’s Ratio (KR), and Nitrate Pollution Index (NPI). Results showed that groundwater in the study area is generally slightly acidic (pH 4.5–6.5) but within acceptable limits for most physicochemical parameters. WQI values for all samples were below 50, indicating good water quality and suitability for irrigation. SAR and KR values were low, suggesting minimal risk of soil structural degradation, while PI values indicated good permeability and favorable infiltration conditions. However, elevated NPI values (>3), especially during the rainy season, suggest significant nitrate contamination risks requiring continuous monitoring. Total hardness values exceeded recommended thresholds, which may pose long-term soil and water quality challenges. Magnesium hazard was generally low, except in Nibo, where higher values may affect soil structure. Overall, the study concludes that groundwater in the area is largely suitable for irrigation, though concerns related to acidity, nitrate pollution, and hardness necessitate proper management and monitoring to ensure sustainable use.