Integrated hydrogeochemical characterization and physicochemical drinking-water quality assessment of the Ildabey Spring, Eyl, Northeastern Somalia

Groundwater quality is a critical concern in arid and semi-arid regions, where communities depend heavily on groundwater and spring systems for drinking-water supply. The hydrochemistry of the Ildabey Spring, Eyl, northeastern Somalia, was characterized using 36 dry-season water observations collected in January 2026 at 12 locations distributed among three spring-flow zones. Major-ion equivalent proportions, weighted arithmetic water quality indices (WQI), ionic charge balance, chloro-alkaline indices, exploratory multivariate analyses and geospatial patterns were assessed. To preserve spatial independence, zone comparisons used the four location-averaged observations per zone. Electrical conductivity increased from 287 ± 11 to 386 ± 13 µS cm⁻¹ and total dissolved solids from 181 ± 8 to 244 ± 10 mg L⁻¹ from the emergence to the downstream collection zone. Calcium contributed 46.6–47.0% of cation equivalents and bicarbonate was the largest anion component. The weighted arithmetic WQI averaged 23.11 ± 2.34, 30.41 ± 2.48 and 36.22 ± 3.05 across Zones A, B and C, respectively, indicating excellent-to-good physicochemical quality under the selected scheme. Negative chloro-alkaline indices were consistent with exchange-related chemical patterns, without establishing a unique reaction pathway. Results establish a site-specific dry-season physicochemical baseline; microbial safety, trace-element risks, seasonal changes and seawater mixing remain unresolved.