Assessment of Groundwater Quality Using the Water Quality Index (WQI) in Woreillu Town, Ethiopia

Groundwater is a vital source of drinking water in Woreillu Town, Ethiopia; however, its quality may be affected by both natural hydrogeochemical processes and anthropogenic activities. This study evaluated the suitability of groundwater for drinking purposes using physicochemical parameters and the Water Quality Index (WQI) approach. Fifteen physicochemical parameters, including temperature, pH, electrical conductivity (EC), total dissolved solids (TDS), total hardness, turbidity, alkalinity, nitrate, phosphate, sulfate, and selected heavy metals (Fe, Cu, Pb, Mn, and Zn), were analyzed from five sampling sites (S1-S5) following standard analytical procedures. The five sampling sites were selected to represent the principal groundwater abstraction points serving the town's population, covering the main spatial distribution of boreholes across the study area. The results showed that most physicochemical parameters were within the World Health Organization (WHO) permissible limits. However, lead (Pb) concentrations exceeded the guideline value (0.01 mg/L) at all sampling sites, indicating significant contamination and potential health risks. Spatially, the highest Pb levels were recorded at S1 (Mume) and S5 (Agamti), sites located in areas of elevated agricultural activity and greater potential for diffuse contamination. Other parameters such as EC, TDS, nitrate, sulfate, copper, manganese, and zinc remained generally low, suggesting limited salinity and weak anthropogenic influence for most water quality indicators. The computed WQI values ranged from 49 to 136, classifying groundwater quality from excellent to poor. Accordingly, S3 and S2 were categorized as excellent and good quality water, respectively, while S1, S4, and S5 were classified as poor. Effective weight analysis revealed that lead (62.58%), pH (11.67%), and turbidity (6.92%) were the most influential parameters contributing to overall water quality deterioration. These findings are broadly consistent with comparable WQI-based studies in Ethiopian and sub-Saharan groundwater systems, where heavy metal contamination-particularly Pb and Fe-frequently dominates WQI deterioration (Karmakar et al., 2024; Das et al., 2025). Overall, the study indicates that although most groundwater sources in Woreillu Town are chemically suitable for drinking, heavy metal contamination-particularly lead-poses a serious public health concern. Continuous monitoring and appropriate management strategies are recommended to ensure safe and sustainable groundwater utilization. A key limitation of this study is its reliance on five sampling sites from a single monitoring campaign conducted in 2019; future studies should incorporate a higher spatial density of sampling points, seasonal assessment, and multivariate statistical analyses to improve representativeness and scientific robustness.