Estimation of groundwater recharge of shallow aquifer on humid environment in Yaounde, Cameroon using hybrid water-fluctuation and hydrochemistry methods

Abstract

A study of environmental chloride and groundwater balance has been carried out in order to estimate their relative value for measuring average groundwater recharge under a humid climatic environment with a relatively shallow water table. The hybrid water fluctuation method allowed the split of the hydrologic year into two seasons of recharge (wet season) and no recharge (dry season) to appraise specific yield during the dry season and, second, to estimate recharge from the water table rise during the wet season. This well elaborated and suitable method has then been used as a standard to assess the effectiveness of the chloride method under forest humid climatic environment. Effective specific yield of 0.08 was obtained for the study area. It reflects an effective basinwide process and is insensitive to local heterogeneities in the aquifer system. The hybrid water fluctuation method gives an average recharge value of 87.14 mm/year at the basin scale, which represents 5.7% of the annual rainfall. Recharge value estimated based on the chloride method varies between 16.24 and 236.95 mm/year with an average value of 108.45 mm/year. It represents 7% of the mean annual precipitation. The discrepancy observed between recharge value estimated by the hybrid water fluctuation and the chloride mass balance methods appears to be very important, which could imply the ineffectiveness of the chloride mass balance method for this present humid environment.

Parameterization and quantification of recharge in crystalline fractured bedrocks in Galicia-Costa (NW Spain)

“…Granitic-gneissic complexes in southern India have a natural recharge rate of 3-15 % of precipitation, partially because of the adverse hydrometeorological factors (Sukhija et al, 1996;Massuel et al, 2007). Similarly, estimations of groundwater recharge of shallow aquifer on crystalline rocks in West Africa are 5-12 % of precipitation (Martin and van de Giesen, 2005;Fouépé Takounjou et al, 2010). …”

Variation in stable isotope ratios of monthly rainfall in the Douala and Yaounde cities, Cameroon: local meteoric lines and relationship to regional precipitation cycle

“…About 60-75 % of the rain that falls in the African tropical forest is re-evaporated as continental moisture (Monteny and Casenave 1989). Higher values ([80 %) have been reported in a zone within the tropical rainforest of Cameron (Sigha-Nkamdjou 1993;Takounjou et al 2011) which include the study area.…”

“…The highest altitude of 1060 m.a.s.l. is Mont Febe (Takounjou et al 2011). Unlike Douala, Yaounde is made up of a crystalline metamorphic formation.…”

“…Unlike Douala, Yaounde is made up of a crystalline metamorphic formation. It is dominated by gneissic rocks that are highly weathered (Temgoua et al 2005;Takounjou et al 2011). The high weathering is due to the high rainfall and warm climatic conditions.…”

An Integrated Field Assessment of Groundwater Recharge

“…In the water level fluctuation method for recharge estimation [10,13,16,[27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43], a rise in the water table, in response to a precipitation-induced recharge event, is converted to an amount of recharge by multiplying the magnitude of the rise by the aquifer's specific yield. The method is attractive because water table measurements are often available, and the method is relatively quick, simple, and easily implemented.…”