GIS-Based Spatial Distribution of Surface Water Quality in Relation to Barge Traffic Intensity in Onne and Port Harcourt Ports, Rivers State, Nigeria

Abstract

Barge transport is an important component of cargo movement in the Eastern Nigerian ports, but spatially explicit evidence on surface-water quality along barge corridors remains limited. This study assessed the spatial distribution of eleven surface-water quality parameters in relation to distance from the jetty at Onne Port and Port Harcourt Port, Rivers State, Nigeria. Surface-water samples were collected from 12 stations at each port during the wet season in July 2026. The parameters analysed were turbidity, total suspended solids (TSS), biochemical oxygen demand (BOD₅), chemical oxygen demand (COD), ammonia (NH₃), lead (Pb), cadmium (Cd), chromium (Cr), copper (Cu), faecal coliform, and total coliform. A composite Pollution Index was calculated using min–max normalisation, and Geographic Information System (GIS) interpolation was used to examine spatial patterns. The interpolated surfaces showed substantial spatial heterogeneity, with localised higher-pollution zones in central sections of the sampled corridors. However, corridor-wide correlation and regression analyses showed that distance from the jetty was not a statistically significant predictor of the composite Pollution Index at either Onne Port (R² = 0.0003, p = .954) or Port Harcourt Port (R² = 0.022, p = .642). The findings therefore indicate that the mapped hotspots should be interpreted as localised spatial patterns rather than evidence of a consistent distance-based or causal effect of barge operations. Hydrodynamic mixing, sediment transport, and non-maritime discharges remain plausible contributing factors. GIS mapping complements station-based analysis by identifying spatially concentrated areas that may warrant targeted environmental monitoring.