Role of non-point sources in the development of a water quality management plan for the Mgeni River catchment

Abstract

Integrated river basin management depends upon information about existing and potential water quality problems. In the Mgeni River basin, the major water quality problems are sediment, nutrient and bacterial with at least 85 percent of the total contamination derived from non-point sources. This paper shows that it is of paramount importance that the development of management objectives and approaches be based on the understanding, quantification and interpretation of the seasonal and spatial variation in export from non-point source areas. Management and analysis requires the grouping of all non-point source areas into diffuse, concentrated and incident sources, with the emphasis on the source area and pollutant delivery rather than the water quality response. Traditionally monitored data is not sufficient for detailed interpretation of non-point source pollution. Comments are made regarding the problems associated with obtaining representative loading data for non-point sources. The choice of appropriate analysis techniques, which assist in the interpretation of the available data, is based upon an assessment of the information requirements for management, the conditions and the water quality problems in the study catchment. GIS-based basin scale and individual source area maps of pollution potential and export are used to support the time-series of catchment export. These techniques will be incorporated into the management information system (MIS).