Use of reconnaissance measurements to establish catchment sediment budgets: a Zambian example.

The sediment budget of a catchment represents a key tool for understanding its sediment dynamics and for developing effective sediment management and control strategies. To date, however, there are few, if any, reliable procedures for predicting the sediment budget of an imgauged catchment. In the absence of such prediction procedures, recourse must be made to direct measurements to provide the necessary information to synthesize the sediment budget. An intensive programme of field measurements would be needed to obtain a detailed sediment budget for a catchment, but reconnaissance measurements can provide sufficient information to synthesize a generalized sediment budget that will be adequate for many requirements. An approach employing such reconnaissance measurements has been developed by the authors and tested in a small (63 km") catchment in southern Zambia. The key components involve: establishing the catchment sediment yield, use of sediment fingerprinting techniques to establish the relative importance of different sediment sources, and use of caesium-137 measurements to obtain information on gross and net soil loss under different land-use types and on rates of flood plain sedimentation. The resulting data can be used to synthesize the catchment sediment budget.