article · Discover Geoscience
Coastal aquifers provide essential fresh water for domestic purposes, but they face increasing threats from climate change, rising sea levels, and excessive extraction. Research in the Northwestern Douala basin in Cameroon evaluated groundwater vulnerability to seawater intrusion using the GALDIT framework alongside hydrogeochemical and ionic ratio analyses. Current findings show low overall vulnerability, with GALDIT index values remaining under four across the basin. However, the southern section, which covers thirty per cent of the area, is comparatively more vulnerable. Under a simulated one-metre sea level rise, this higher-vulnerability zone expands to cover half of the territory, reaching central sectors. Hydrochemical indicators, including ionic ratios and USSL classifications, show low salinity and demonstrate that the aquifer is undergoing a natural freshening process, with existing contamination primarily driven by human activities rather than marine intrusion.
Coastal populations rely heavily on groundwater for drinking water and daily needs. Understanding how sea level rise affects these aquifers helps local authorities anticipate future water security risks. Identifying specific vulnerable zones allows communities to protect freshwater reserves, prevent saline contamination, and separate human-caused pollution from natural seawater encroachment.
The findings can inform coastal groundwater management programmes, environmental consultancies, and water utilities planning long-term extraction infrastructure. While the assessment demonstrates an applied environmental diagnostic method tested in a specific basin, it represents early-stage decision-support research. Converting this work into practical use would require regional planning bodies or water management authorities to adopt the vulnerability modelling into spatial monitoring and permitting workflows.
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Aquifer systems in coastal areas provide huge volumes of fresh water for domestic use globally. Seawater intrusion poses a significant challenge to this fresh water reservoir, resulting from excessive extraction, sea level rise, and changing climates. This present study employed GALDIT model and impacts of sea level rise to evaluate the susceptibility of groundwater to contamination by seawater in Northwestern Douala basin. This study also utilized ionic proportions of Na/Cl, Ca/Mg, the Simpson ratio, BEX, alongside USSL. The results revealed the GALDIT index value varied between 3.5 and 3.8, suggesting that the study area exhibits low vulnerability to saline water, as the values are below 5. The southern portion of the study domain, which constitutes 30% of the total area, exhibited higher values of 3.8. According to the GALDIT index, this region is more susceptible to seawater intrusion compared to other areas. The impact of a 1-m rise in sea level attributed to changes in climate showed that the area with higher values expanded from 30 to 50% of the study region, encompassing the southern part and reaching the central part of the area under investigation. Results from ionic ratios revealed that groundwater contamination is mainly from anthropogenic sources, the USSL classification revealed low salinity and the BEX revealed groundwater within the investigated region is basically undergoing freshening process. The Hydrogeochemical facies showed a predominance of alkaline earth elements over alkali metals (Ca + Mg > Na + K) and a prevalence of weak acidic anions over strong acidic anions (HCO3 > Cl + SO4) which is an indication of low salinization. Significantly, this study would aid to delineate areas with greater risk to sea-water intrusion from the GALDIT model, provide an understanding of the hydrogeochemical dynamics in the study area, and equally serves as a basis for sustainable groundwater management and environmental conservation efforts.
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DOI: 10.1007/s44288-025-00159-w
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