Environmental factors controlling contamination and vulnerability of water alternative supply points in Lefock semi-urban watershed, West Cameroon

Abstract Due to the poorly managed water network of the Dschang municipality (West Cameroun), the peri-urban population of the Lefock watershed, frequently, consumes doubtful quality water from alternative supply points (WASPs): spring, well, river, borehole. In this context, the present study aimed to explore the influence of close environment on the possible contamination of these resources. For this purpose, 22 WASPs were characterized (within a 10 m radius of the point) both from physiographic (nature of bedrock, water supply utility, soil type, land use) and anthropogenic (presence of pit latrines, domestic wastewater, domestic breeding, agricultural activities, wild garbage dump, washing clothes on-site). Then, chemical (NO3−, NH4+, PO43−) and bacteriological (faecal coliforms, faecal streptococci, total coliforms, and E. coli) contamination parameters were analyzed and compared with the World Health Organisation (WHO) standards. Multiple Factor Analysis (MFA) was done, using water quality variables as input combined with environmental data as supplementary data. It revealed that waters from WASPs were generally of very poor bacterial quality, due to proximity with pit latrines, domestic wastewaters, and/or agricultural plots. NO3− is exceptionally high where WASPs are close to agricultural plots and/or domestic wastewaters. The MFA showed that the chemical degradation of WASP mostly results from wider scale processes and is representative of diffuse (and likely long-term) impacts on the resource. In contrast, bacteriological contaminations were better governed by immediate contexts and appears to result from the combination of anthropogenic and physiographic constraints. Regarding vulnerability, the type of soil and the nature of the WASPs are the main influencing factors. The hydromorphic context accentuates the vulnerability, while the order of increasing vulnerability related to the type of WASPs is: spring - well and borehole - river. These results indicate that poor water management, combined with a limited consideration of local environmental specificities threatens the security and sustainability of this resource in semi-urbanized zones over heterogeneous aquifers, and argue for a twofold education effort for managers and end-users of the resource.