Influence of Gully Erosion on Groundwater Quality in South Eastern Nigeria

Abstract

Gully erosion is an environmental challenge that can affect groundwater resources in South Eastern Nigeria by increasing sediment transport, enhancing weathering and mobilising dissolved constituents into aquifer systems. This study evaluated its influence on groundwater quality in erosion-prone communities using physicochemical parameters, major ions, heavy metals and seasonal variation. Groundwater samples were collected from ten boreholes at varying distances from active gully erosion sites during wet and dry seasons. Field and laboratory procedures were used to determine physicochemical parameters, while major ions and heavy metals were analysed in accordance with Standard Methods for the Examination of Water and Wastewater. Descriptive statistics, Pearson’s correlation analysis and seasonal comparisons were used to assess erosion-related effects on groundwater quality. Groundwater temperature ranged from 25.8 to 29.6°C, while pH varied from 5.42 to 7.21, indicating slightly acidic to neutral conditions. Electrical conductivity ranged from 118 to 912 µS/cm, total dissolved solids from 74 to 584 mg/L and turbidity from 0.84 to 18.62 NTU. Calcium (14.8–72.6 mg/L) and bicarbonate (42.6–186.8 mg/L) were the dominant cation and anion, respectively. Iron concentrations ranged from 0.06 to 1.12 mg/L, while maximum lead and cadmium concentrations were 0.024 and 0.008 mg/L, respectively. Boreholes within 50 m of active gullies recorded the highest turbidity, total suspended solids and iron concentrations. Turbidity strongly correlated with total suspended solids (r = 0.954), indicating the contribution of erosion-derived sediments. The findings show that active gully erosion is associated with groundwater quality deterioration, especially during the wet season and in boreholes closest to erosion channels.