Water quality characteristics of Densu River basin in south-east Ghana.

Water quality of the Densu River was studied by determining the levels of various physico-chemical parameters including trace metals for planning of the basin. The pH range (7.40-8.22) fell within the natural background level 6.5-8.5. The river was moderately hard with high turbidity due to poor farming practices, which result in large quantities of topsoil ending up in the river after rains. The river waters were well oxygenated with a mean DO concentration of 6.3 mg/l. Nitrogen and phosphorus levels were below their natural background values. The Densu River showed an overall ionic dominance pattern of Na > Ca > K > Mg and Cl > HCO(3) > SO(4), a pattern which is an intermediate between fresh and sea water systems. The mean concentrations of metals for the basin followed the order: Fe > Mn > Zn > Pb > Cu > Cd. 84.6% of the sampling sites exceeded the background values of 0.3 mg/l and 0.1 mg/l for Fe and Mn respectively. Other metals Zn, Pb, Cu and Cd were all below their background levels indicating the river is unpolluted with respect to these metals. Water Quality index performed on the data depicted that River Densu is of poor to fairly good water quality. Regular water quality monitoring is recommended.