Yaoundé, Cameroon
Yaoundé, Cameroon

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Ako A.A.,Hydrological Research Center | Shimada J.,Kumamoto University | Hosono T.,Kumamoto University | Kagabu M.,Kumamoto University | And 7 more authors.
Journal of Hydrology | Year: 2013

We used environmental tracers (δD, δ18O, 3H and chlorofluorocarbons (CFCs)) to establish the groundwater flow system within the Mount Cameroon area: a 4090m high active entirely alkaline volcano located within a humid equatorial region. Seventy-five ground and surface water samples (68 spring samples, 6 borehole samples and 1 stream sample) were collected around the volcano during the wet (October-November 2010) and dry seasons (January-February 2010) as well as 10 rain samples in June-September 2010 in order to establish recharge elevations, apparent ages (residence times) and groundwater flow system in the fractured volcanic (basaltic) aquifers. The δ18O and δD composition of rainwater and groundwater in the Mount Cameroon area fit the Douala Local Meteoric Water Line (DLMWL). The recharge elevations of the individual springs were calculated from their δ18O-values and the equation of the altitude gradient (-0.16‰ δ18O/100m) of precipitation on the mountain. For springs sampled during the two seasons, dry season samples have higher recharge elevations than rainy season samples. Seasonal variation exists in the tritium values as rainy season samples systemically are higher than those of the dry season samples This implies the input of new water from the rain causing the groundwater system to rejuvenate. Apparent ages for the Mount Cameroon springs calculated from CFCs based on the Piston Flow model range from 10 to approximately 57years. CFC apparent ages for rainy season samples are systemically younger than those of dry season samples. There is seasonal variation in groundwater flow system in the Mount Cameroon area and also along the different flanks of the volcano. The groundwater flow system is conceptualized by 2 models; a Bypass/piston flow model for the flow system during the rainy season and a binary mixing/piston flow model characterizes the flow system during the dry season. © 2013 Elsevier B.V.


Ako A.A.,Kumamoto University | Ako A.A.,Hydrological Research Center | Shimada J.,Kumamoto University | Ichiyanagi K.,Kumamoto University | And 4 more authors.
Journal of Environmental Hydrology | Year: 2010

The isotope hydrology and hydrochemistry of surface and groundwater of the Banana Plain were studied to trace the origin of groundwaters and evaluate the major ion chemistry and geochemical processes controlling water composition. Water samples from rain, streams, lake, springs, wells and boreholes were collected and analyzed for major ions, stable isotopes, tritium and dissolved silica. 18O and 2H data indicate that groundwater has been recharged by meteoric water without significantly being affected by evaporative processes either during or after the recharge process. Evaluation of the groundwater residence time demonstrated that groundwater in the Banana Plain aquifers should be considered as a renewable water resource. In general the waters are Ca/HCO3 and Ca-Mg-Na/HCO3 dominated. Weathering of silicate minerals controls the concentration of major ions such as calcium, magnesium, sodium and potassium while NO3 and Cl are of anthropogenic origin. Chemical composition of the groundwater in this area is influenced by rock-water interactions.

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