Summary
Douala, Cameroon has been experiencing repeated cholera epidemics due to contaminated groundwater. The present study is to characterize the sedimentary aquifer system of Douala using time domain electromagnetic sounding (TDEM) and magnetic resonance sounding (MRS) for better understanding of the aquifer system to explore cleaner groundwater resources in the region. The TDEM and MRS results show good agreement of aquifer structure with the observed water tables from nearby wells and spring water. The existence of a deeper aquifer from the survey may provide a solution to develop a new fresh groundwater well field for the prevention of future cholera outbreaks in the region. As part of the Geoscientists Without Borders project, the present study also emphasizes capacity building of geophysical applications in the region. The project successfully trained eight African graduate students to master the TDEM and MRS techniques with involvement of undergraduate students from the St. Jerome Catholic University of Douala.
Introduction
Douala is the economic capital of Cameroon with a population of about 2 million. In 2004, Cameroon experienced a large cholera outbreak with over 8000 reported cases in the Littoral and West regions. According to the WHO (2012), the outbreak started in Bepanda in the northwest of Douala and spread rapidly to the entire city of Douala. Repeated epidemics continued to occur in Douala especially between 2009 and 2012. Contaminated groundwater is the major source of cholera disease in Douala as residents use groundwater for drinking and daily activities. It is observed that the leachate from household sewage system contaminates shallow groundwater in a local well, of which water depth is around 5-10 m.
The major goal of the present study is to characterize the sedimentary basin in Douala by using two geophysical techniques – time domain electromagnetic sounding (TDEM) and magnetic resonance sounding (MRS) for better understanding of aquifer systems, which may provide a solution for developing fresh and clean groundwater resources in the future. The present study is the very first results of the Geoscientist Without Borders (GWB) project with a team of scientists and students from the US, France, Nigeria, Niger, Chad, and the hometown Cameroon. To meet the goals of GWB, the study emphasized not only the scientific findings, but also capacity building to meet humanitarian needs in the region. The first field campaign took place from January 18th, 2015 to January 31st, 2015 for two weeks in Douala. Five scientists (mentors) led the campaign with eight African graduate students and twenty-two undergraduate students from the St. Jerome University of Douala. This team composition with African students promoted effective capacity building of geophysical applications as the mentors trained the African graduate students, who in turn guided the undergraduate students from the St. Jerome to learn geophysical techniques under the supervision of mentors.
