INFLUENCE OF THE WATERSHED GEOLOGY ON RIVER DISCHARGE INTO THE WOURI ESTUARY, CAMEROON

The physico-chemical measurements of the Dibamba River and Mungo River were conducted in the highly urbanized Wouri estuary in Cameroon to assess the spatial variability of the water chemistry. To the east, the Dibamba River drains metamorphic rocks while to the west the Mungo River primarily drains volcanic outpours of Mt. Cameroon. The focus was on evaluating the rate of change in key physico-chemical parameters of water samples such as salinity, dissolved oxygen (DO), alkalinity, and pH. We collected 13 water samples from a segment of the Dibamba River and 10 samples from a segment of the Mungo River at intervals of 2 and 3 km between sampling locations, respectively. Measurements show that salinity decreased from 6.80 to 0.02 PSU over 16 km into the Dibamba River from the open estuary while it decreased from 2.03 to 0.02 PSU over 11 km into the Mungo River. DO showed a mean value of 4.8 ± 0.4 and 4.7 ± 0.4 ppm, for the Mungo and Dibamba respectively. The pH decreased from 7.51 to 5.9 from the open estuary into the Dibamba while the Mungo showed an average pH of 6.6. Alkalinity varied from 5 and 20 mg/L in CaCO3 in the Dibamba River and varied from 16 to 28 mg/L in CaCO3 in the Mungo River. The Dibamba River showed greater variations in physico-chemical parameters (salinity, pH, and alkalinity). We suggest these variations may be attributed to the greater mixing of the open estuary with the Dibamba River due to the wider opening of its channel in contrast to the constricted channel of the Mungo River.