Performance during industry discharge events: Hunter River Salinity Trading Scheme performance report 2022-23

Water discharged and total flow

A total of 49,596ML of saline water was discharged into the Hunter River by 11 Scheme participants during July 2022 to June 2023. This represented only 2% of the total flow of water past Singleton for the same period (2,549,470ML).

A comparison of monthly industry discharge and Hunter River flow volumes is shown in Figure 3, below.

Total salt load

A total of 103,374 tonnes of salt was discharged to the Hunter River by 11 Scheme participants during July 2022 to June 2023. Participants used 37% of the TAD (278,200 tonnes), an increase from 27% from the previous year², highlighting that participants are using more discharge opportunities to manage onsite water due to higher rainfall.

2. The total salt discharged by industry during both high and flood flows (saline water is still discharged into the river during flood flows).

Saline discharges

Industry discharges represented only 14% of the total salt load that flowed past Singleton and this was predominantly in July 2022 to December 2022 due to the higher rainfall and number of discharge opportunities. Figure 5, below, shows the proportion of industry discharges with river flow and river salt loads for each quarter of 2022–23.

The average yearly electrical conductivity (EC - measurement of salinity) for each sector is in Table 5, below. The upper sector experienced a 7% increase in average EC, while average EC in the middle and lower sectors increased by 20% and 12% respectively from 2021–22.

Table 5 Comparison of average annual EC for each sector.

Though there was a significant increase in total salt load and participant discharges compared to prior years (refer to grey shaded columns in Figures 4 and 5, representing total flow past Singleton), largely due to higher rainfall, this did not result in a significant increase in average salinity (Table 5). The increase in average EC is due to lower rainfall in the second half of the 2022-23 Financial Year. However, this was not due to participant discharges (Figure 5). This demonstrates how the Scheme effectively manages the water salinity by restricting and managing saline discharges from industry.