SEASONAL HYDROCHEMICAL VARIABILITY AND IMPLICATIONS FOR GROUNDWATER QUALITY NEAR AN OPEN DUMPSITE IN ENUGU URBAN, SOUTHEASTERN NIGERIA

Groundwater constitutes a major source of domestic water supply in many developing regions; however, anthropogenic activities, such as open waste disposal, threaten its quality. This study evaluates the seasonal hydrochemical variability of groundwater around the open Ugwuaji dumpsite in Enugu, Southeastern Nigeria, focusing on physicochemical parameters and their implications for water quality. We collected groundwater samples from hand-dug wells within the dumpsite vicinity and a control well during the wet and dry seasons. Eleven physicochemical parameters—temperature, pH, electrical conductivity (EC), total solids (TS), total suspended solids (TSS), total dissolved solids (TDS), chloride (Cl⁻), total hardness (TH), dissolved oxygen (DO), sulfate (SO₄²⁻), and nitrate (NO₃⁻) - were analyzed using standard laboratory procedures. The results revealed pronounced seasonal variations, with hand-dug wells showing significantly wider concentration ranges than the control well. Wet season samples recorded elevated mean values for TS, TSS, TDS, and chloride, attributed to enhance leachate infiltration, while dry season samples exhibited higher EC, TH, and nitrate due to evapoconcentration effects. Chloride concentrations exceeded permissible limits in several samples, whereas pH values indicated acidic conditions during the dry season. Coefficient of variation analysis revealed greater variability in the wet season, particularly for chloride and EC, whereas nitrate and TDS dominated the variability in the dry season. The findings demonstrate that seasonal hydrochemical processes and waste-derived contamination significantly influence groundwater quality around the open Ugwuaji dumpsite. This study highlights the vulnerability of shallow aquifers in dumpsite environments and underscores the need for continuous monitoring, improved waste management practices, and provision of safe alternative water sources.