Groundwater contamination due to irrigation of treated sewage effluent in the Werribee delta

The Werribee River, groundwater and Melbourne's treated sewage effluent (or recycled water) are used for irrigation water in the Werribee Delta. Groundwater beneath the Werribee delta may be contaminated by the recycled water. The mixing ratios of the sea water, upstream groundwater and recycled waters for delta groundwater were calculated from water chemistry. The mixing ratio of the recycled water varied from 10 to 30 % at all depths and delta groundwater was found to be largely comprised by irrigated recycled water. The NO3 - contamination of delta groundwater is thought to be caused by recycled water and agricultural use of fertilizers. A high mixing ratio of sea water was found at 30 m in depth and this zone was thought to be a salt-water wedg