Water Quality Issue	Possible Causes
Low PH in many agricultural drains and creeks on the Clarence Floodplain eg Shark Creek. (Water Quality of the Lower Richmond and Clarence Floodplains - report by E Scribner, Fisheries research Institute. Streamwatch testing by Maclean High.)	Acid runoff from acid sulfate soils.
High levels of faecal coliforms near Grafton associated with storm events. (Bacteriological Water Quality in the Clarence river at Grafton, 1993/94 - report by Lee Bowling, DLWC).	Stormwater runnoff from Grafton City - particularly in storm events when there are low flows in the river.
High suspended sediment loads throughout the catchment in high flow events. (Water quality in the Clarence River - SPCC northern Rivers Study No.3, 1987).	Gully erosion in highly disperible soil types. Roadside erosion. Riverbank erosion. Erosion from intensive agriculture.
Poor water quality (ie high nutrient concentrations, low dissolved oxygen) in the Clarence River North of Tabulam at times. (The Northern Rivers - A Water Quality Assessment - 1996 EPA report).	Low river flows. Nutrient discharge from towns and agriculture.
Poor water quality (ie high nutrient concentrations, low dissolved oxygen) in some sections of the Orara river during low flows. (The Northern Rivers - A Water Quality Assessment - 1996 EPA report. Coffs Harbour Water Supply Augmentation - Water Quality Report).	High rate of water extraction from the river. Nutrient discharge from towns and agriculture.
High levels of some heavy metals in Plumbago creek near Drake, particularly in the Sawpit Creek sub-catchment. (Plumbago Creek Study - EPA)	Past mining activities.
High nutrient levels in Wooloweyah Lagoon (Lancaster, 1990 - Unpublished thesis; Williams, 1987 - Northern Rivers Fisheries Report)	Septic systems. Stormwater runofff. Agricultural runoff.
Poor water clarity in Wooloweyah Lagoon (Lancaster, 1990 - Unpublished thesis; Williams, 1987 - Northern Rivers Fisheries Report)	Shallow nature of water body, and resuspension of sediments by wind and wave action. Excessive growth of algae.
Algal blooms and excessive algal growth in the upper Clarence, Grafton area, Broadwater, and some channels in the estuary. (DLWC reports).	Nutrient discharge from various sources including stormwater, agriculture, industry, and septic systems. Often associated with low river flows, or poor tidal flushing.
High nutrient loads and low dissolved oxygen in the Southgate/Alumy and Alipou/Musk Valley creeks. (Water quality in the Clarence River - SPCC northern Rivers Study No.3, 1987. Streamwatch sampling, South Grafton High School).	Storm water runoff from Grafton City. Discharge from sewerage treatment plants.
High levels of faecal coliforms at times in the Clarence estuary adjacent to Iluka. (The Northern Rivers - A Water Quality Assessment - 1996 EPA report, Council testing)	Contamination from septic systems. Storm water runoff.
High levels of faecal coliforms in the water supply and swimming holes of the Tabulam community (Woodward-Clyde 1994 - Plumbago Ck Catchment Study)	Low river flows. Contamination from septic systems. Inadequately treated discharge from sewerage treatment plants.