Suspended sediment transport characteristics of upper Kaleya river,Southern Zambia
Sichingabula, Henry Walling, D.E. Collins, A.L. Leeks, Graham G.L.
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Soil erosion has many negative impacts on agriculture and other land related activities and so there is an urgent need to find ways of controlling it. In a bid to increase the understanding of soil erosion and sediment transport processes in Zambia, a project, which was funded by the UK Department for International Development, was conducted in the Upper Kaleya River catchment, southern Zambia, between 1997 and 2000. Being primarily concerned with sediment budgeting, this project necessarily involved the collection of discharge and suspended sediment load data for estimating sediment yields from the study river. This paper reports the suspended sediment transport characteristics of Upper Kaleya River during the study period. Analysis of the data collected at the study catchment outlet, at Roadbridge, revealed that discharge ranged from zero, during some dry season months, to 3.65 m3 s-1, with a daily mean discharge of 0.406 m3 s-1. The corresponding suspended sediment loads ranged from zero to 253.9 tonnes, with a mean of 3.15 tonnes per day. Magnitude-frequency analysis revealed that the flow responsible for transporting most of the suspended sediment load was 1.44 m3 s-1. This discharge represented 1.5 % of the time. During the study period, the total cumulative discharge was estimated at 34.8 million m3, whilst the total suspended sediment load was estimated at 3,130 tonnes. It is concluded that, though the Upper Kaleya River catchment is small, measured discharge and suspended sediment fluxes are reasonably high. Ways of controlling soil loss and of improving water resource protection should therefore be encouraged among the local farmers. There is also an urgent need to conduct this type of research in larger catchments in Zambia and in southern Africa region in order that national and regional sediment-related control measures can be designed and implemented. KEY WORDS: Catchment, effective discharge, magnitude-frequency analysis, river discharge, soil erosion, suspended sediment load.