most rivers exhibit a high degree of degradation particularly within the murraydarling catchment australia s main agricultural producing region drinking water quality is impaired in many locations and coastal regions downstream of large agricultural areas suffer from sediment and nutrient loadings in terms of the environmental health of the great barrier reef gbr recent research indicates that quantities of sediment phosphorus and nitrogen entering the gbr have been increasing with agriculture a key contributor to water quality issues in the gbr rolfe and windle but given the lack of a national monitoring system it is difficult to assess national trends in water quality related to agriculture oecd a there are expensive restoration cleanups going on in some iconic lakes and there are questions over the state of groundwater at a national level diffuse discharges now greatly exceed point source pollution