This tool helps you calculate the minimum irrigation area required to sustainably apply wastewater based on its organic loading. It follows the methodology outlined in the NSW Department of Environment and Conservation (2003) Use of effluent by irrigation, and is designed to prevent overloading soils with organic matter.
In a well-managed irrigation scheme, organic matter can enhance soil fertility and support plant growth. However, excessive application can clog soil pores, reduce oxygen availability, and lead to odorous, anaerobic conditions. This calculator uses the biological oxygen demand (BOD) of the wastewater and the irrigation rate (from a water balance) to estimate the average maximum daily organic loading rate.
If you can demonstrate that the application rate is sustainable, you may not need to reduce the BOD of the wastewater. This tool supports evidence-based decisions for land application of wastewater in a way that protects soil health and environmental quality.
Refer to Water quality protection note no. 22 for further guidance.
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