Characterising cause-and-effect relationships in support of catchment water quality management

In the late 1980s the Department of Water Affairs and Forestry in South Africa initiated an ongoing process of reassessing its approach to water quality management. Fundamental to this new approach is the recognision of the need for catchment water quality management. Yet, in spite of a wide appreciation of the importance of catchment management few, if any, plans have been implemented. This is at least in part due to the inability, in practice, to reconcile the Department's water quality management policy with the processes which determine water quality in the catchment. Strategies and management practices which address water quality problems must be aimed at these processes. This paper highlights four generic processes which determine water quality in the catchment. These processes are production, delivery, transport, and use. Management of these four generic processes in sequence support a hierarchy of pollution prevention, impact minimisation, management of the assimilative capacity, and lastly management of the symptoms of pollution. This paper proposes that a management approach based on the characterisation and quantification of each of these processes forms a sound basis for catchment water quality management. This characterisation reconciles water quality management policies with the practices which address water quality problems in the catchment.