Performance during industry discharge events

Hunter River Salinity Trading Scheme Performance Report 2024–25.

Water discharged and total flow

A total of 9,516 ML of saline water was discharged into the Hunter River by six Scheme participants across 80 river registers during the 2024–25 financial year. This represented 0.9% of the total flow of water past Singleton for the same period (1,035,939 ML).

In the 2022–23 financial year an unprecedented 230 river registers were published, which represented 2% of the total flow past Singleton (49,596 ML). While in the 2023–24 financial year only 13 river registers were published which represented 0.2% of the total flow past Singleton (189,029 ML). This highlights the interannual variability in discharge opportunities that can occur, depending on catchment rainfall and river conditions.

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

Table 3 Monthly industry discharge of salt (ML and tonnes) compared with flow (ML) past Singleton, 2024–2025

Total salt load discharged

Figure 1 shows the tonnes of salt annually discharged past Singleton over a 10-year period.

Overall, a total of 16,570 tonnes of salt were discharged to the Hunter River by six scheme participants during July 2024 to June 2025, much more than the previous year. Proportionally, participants used 15.2% of the TAD (108,800 tonnes) compared to 9.6% of the TAD (1291 tonnes) in the previous year.

Figure 1: Comparison of annual industry discharge, TAD, Hunter River salt load and flow past Singleton, 2014-2025. * Flood flow TAD was removed from 2021 onwards. The higher figures represented in the 2020-21 data include flood flow TAD.

Table 4 shows the relationship between the natural salt load of the Hunter River and the discharges made by industry, over a 10-year period, as a percentage.

Table 4 Proportion of industry salt discharges in Hunter River salt loads

Saline discharges

In 2024–25, average daily flow past Singleton (ML/day) was approximately 70% or 1,160 ML/d greater than the average flow since 2013 (1,678 ML/day). While this meant there were several opportunities to discharge across the year, most of these opportunities occurred following the significant rainfall and inflows that occurred in the final two months of the financial year. Industry discharges in 2024–25 represented 6.0% of the total salt load that flowed past Singleton. 

Figure 2 below shows the breakdown of industry discharges with river flow and river salt loads for each quarter of 2024–25.

Figure 2: Comparison of quarterly industry discharge, TAD, Hunter River salt load and flow past Singleton for 2024–25

The average yearly EC for each sector is shown in Table 5 from 2015 onwards. The average EC in the upper sector of the river for the 2024–2025 period decreased slightly from the previous year, while the middle and lower sectors notably decreased from above to below the 900 EC threshold. 

Table 5 Comparison of average annual EC for each sector 2015–25