Siltation of river channels, lakes and reservoires present a credible threat to river basin ecosystem service provision and water security. River silt originates  in the catchment and the primary driver for mobilisation and translocation downstream is agriculture where loss of soil from slopes threatens food security. Knowledge of sediment source, transfer and residence time dynamics is critical to inform management for future food and water security and cutting edge nuclear techniques have been developed in a joint UN food and Agriculture Organisation and International Atomic Energy Agency Coordinated Research Programme to trace river silt back to source.