Influence of seasonal dynamics on groundwater resources quality in semitropical urban zone: case of the Biyémé upper stream catchment (Yaounde, Cameroon)

Abstract

Located at 3°51’97” to 3°49’97” N and 11°28’85” to 11°29’89” E in the SW of Yaounde, the Biyeme upper stream catchment covers a surface area of 500 ha. It harbours a population of about 400,000 people whose major modes of water supply are wells and springs. The main objective of this research was to study the groundwater quality through combined piezometric and physicochemical and bacteriological data interpretations. From July 2008 to June 2009, 16 wells and 05 springs within the study area were selected and monitored on a bimonthly basis. Results showed low mean annual amplitude of the water table, which varies between 0.49 m for wells in lowlands to 1.30 m for wells in the ridge. Almost 97% of wells and 10% of springs had values of nitrates higher than the 11.36 N-NO3 - guideline recommended by WHO for drinkable water, especially during dry seasons. This underground water also revealed microbial contamination, with values of faecal indicators higher than the 0 UFC/100 ml recommended by WHO, but mostly during raining seasons. Anarchic urbanization and inadequate hygiene conditions are factors enhancing the sanitary risk of these water points. Keywords : Biyeme catchment, hydrodynamics, sanitary risk, seasons, underground water, water quality.