Stable Isotope Analysis of Groundwater Recharge Sources and Mixing Processes on Mount Cameroon’s Southern Flank

Abstract

Stable isotope (δ¹⁸O, δD) and hydrochemical analyses were integrated to investigate groundwater recharge sources and sustainability in the volcanic aquifer along Mount Cameroon's southern flank. This region, characterized by high population density and extensive agro-industrial activities, faces escalating pressure on its groundwater resources due to climate change and anthropogenic impacts. The study examined 30 groundwater sources, and 14 monthly precipitation samples collected between December 2022 and November 2023. Results indicate that groundwater is primarily of meteoric origin, with isotopic compositions clustering near the Global Meteoric Water Line (GMWL), suggesting minimal evaporation effects. Precipitation δ¹⁸O values ranged from -6.11‰ to -0.99‰, with a weighted mean of -3.22‰, while groundwater δ¹⁸O ranged from -6.83‰ to -2.71‰, with a mean of -4.72. Elevated deuterium excess (d-excess: 13.18–15.60‰) further delineates dual recharge contributions from direct Atlantic precipitation and recycled continental moisture, while the absence of altitudinal δ¹⁸O trends (160–961 m) confirms efficient hydrological mixing across the aquifer system. Groundwater temperatures closely mirrored ambient air temperatures, suggesting rapid recharge and shallow circulation within the aquifer. These findings provide a crucial baseline for the sustainable management of groundwater resources in this vulnerable volcanic environment, emphasizing the need for climate-resilient water policies and protection of recharge areas.