GROUNDWATER VULNERABILITY ASSESSMENT USING SUSCEPTIBILITY INDEX (SI) METHOD IN UGHELLI, NIGER DELTA, NIGERIA.

Groundwater plays a vital role in supporting human activities and ecological systems, particularly in semi-arid and urbanizing regions like Ughelli in the Niger Delta, Nigeria. This study assesses the vulnerability of groundwater in Ughelli to pollution using the Susceptibility Index (SI) method. The region’s aquifers exhibit varying depths, classified into five categories ranging from 2.2 to over 11 meters, with low susceptibility to contamination. The area’s gentle slope and low-lying coastal plain are critical factors influencing groundwater dynamics. Water samples was collected from five (5) Locations; The locations of interest (areas where the various data were collected from) are: Otovwodo, Agbarho Oto, Ekrejeba, Afiesere and Otokutu and analyzed for physicochemical parameters and heavy metal concentrations. Laboratory analysis revealed a mean groundwater temperature of 24.5°C, Biochemical Oxygen Demand (BOD) averaging 1.96 mg/L, and Chemical Oxygen Demand (COD) with a mean value of 4.69 mg/L. Chloride levels were recorded at an average of 15.75 mg/L, while nitrate concentrations were measured at 0.59 mg/L, both significantly below the World Health Organization (WHO) permissible limits. Calcium concentrations averaged 4.481 levels indicated mg/L, further confirming groundwater quality within safe WHO standards. Heavy metal analysis negligible of contaminants, reinforcing the aquifer's resilience to pollution. The study identified five distinct land use classes—built areas, bare ground, flooded areas, forests, and pp land—each influencing groundwater quality and recharge potential differently. Geographic Information Systems (GIS) tools, including ArcGIS, GMS, and HEC-HMS, were employed for mapping and analyzing critical hydrogeological parameters, such as aquifer media, effective recharge, topographic slope, and land use patterns. The findings emphasize the need for proactive groundwater management strategies, including regular monitoring, controlled agricultural practices, and sustainable land use planning, to preserve this essential resource. The results highlight the utility of the Susceptibility Index (SI) method for groundwater vulnerability assessments in complex hydrogeological settings like Ughelli. This research serves as a foundation for improving groundwater resource management, ensuring water quality, and promoting environmental sustainability in the region.