Effect of some biological and physico-chemical factors on the water quality of river Ankobra and its major tributaries
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Date
2008-08-11
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Abstract
The absence of treated piped-borne water in the Wassa West District and the reliance of communities on River Ankobra as the source of drinking water make its quality important. Water from Mansi, Bonsa and Fure tributaries; up and down streams of Mansi –Ankobra confluence; up and down streams of Bonsa-Ankobra confluence; and the up and down streams of Fure-Ankobra confluence were sampled. Water sampled from these sampling sites were accessed for pH, Conductivity, Total Dissolved and Suspended Solids, Cyanide, Biochemical Oxygen Demand, Turbidity, Total and Faecal Coliforms, over a six month period. Among the sampling sites, Mansi tributary and upstream of Fure-Ankobra confluence recorded high levels of most of the parameters analyzed. Mansi tributary recorded mean Turbidity level of 199.35 NTU, TSS of 74.58 mg/l, and BOD of 2.37 mg/l with the upstream of Ankobra–Fure confluence also recording approximately the same mean levels of Turbidity (281.8 NTU), TSS (73.75 mg/l), and BOD (2.04 mg/l) as Mansi tributary. Additionally, upstream of Fure–Ankobra confluence recorded mean Conductivity levels of 167.19 µs/cm; TDS of 83.61 mg/l; with Total and Faecal Coliforms of 7.09 and 5.17 Geomean/100ml respectively. Among the parameters analyzed pH, TSS, Turbidity, Total and Faecal Coliforms levels did not meet WHO standards for drinking water. Although one expects high levels of cyanide in Mansi tributary, due to occasional cyanide spillage in its sub-tributaries, its level and that of the other sampling sites were below detection limit. Periods of rainfall observed during sampling increased the levels of the parameters analyzed especially within Mansi tributary. The pollution of Ankobra Basin correlates with areas of intense human activities, such as illegal mining activities within the upstream of Fure-Ankobra confluence and run-off water from the activities of Golden Star Resources Limited silting the Mansi tributary. Whiles Fure and Bonsa tributaries contributed significantly to reducing (P<0.05) turbidity in the river Ankobra, Mansi tributary significantly increased (P<0.01) turbidity levels in it. It is recommended that both tributaries and the river should have 100 metre buffer zones with reforestation in the degraded portions and Community Biodiversity Organizations formed and empowered to guard the demarcated buffer zones from anthropogenic activities.
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A thesis submitted to the Department of Theoretical & Applied Biology, Faculty of Bioscience, College of Science, Kwame Nkrumah University of Science & Technology, Kumasi in partial fulfilment of the requirements for the degree of Master of Science (Environmental Science)