Performance in each sector

Hunter River Salinity Trading Scheme Performance Report 2024–25.

The sections below cover annual salinity and flow information for the upper, middle and lower sectors. Salinity levels are compared with the established salinity targets. Salinity remained below the sector targets during periods of industry discharge, demonstrating the Scheme’s effectiveness.

Upper sector: Hunter River upstream of Denman

Figure 3 shows the maximum daily salinity, minimum daily river flow and the high flow and flood flow salinity target thresholds in the upper sector for the 2024–25 period. No significant flows were observed in the upper catchment for most of the financial year however the high rainfall in May 2025 produced good inflows from Rochel and Pages River. During May-June the maximum observed peak flow at Pages River was around 38,300ML/day. There were 51 discharge opportunities in the upper sector across the year, but only one small discharge (2.55 salt tonnes), in May 2025.

Figure 3: Daily average salinity and flow: Hunter River upstream of Denham for 2024–25

Natural ambient salinity in the upper sector is lower than the middle and lower sector, with the upper sector EC target of 600µS/cm. Average annual salinity in the upper sector for the period was 675 µS/cm, while the average across 2015-2025 was 618 µS/cm.  

Middle sector: From Denman to the junction of the Hunter River and Glennies Creek

There were two significant inflow events from the Goulburn River and Wybong Creek, between April-June 2025. The observed maximum daily flow was approximately 14,400 ML/d at Goulburn River gauge and 4,700 ML/d at Wybong Creek gauge during the May-June event. 

Figure 4 shows the maximum daily salinity, minimum daily river flow and high flow salinity threshold in the middle sector for the 2024–25 period.

Figure 4: Daily average salinity and flow: Hunter River upstream of Glennies Creek for 2024–25

There was a total of 42 discharges in the middle sector, all in the fourth quarter, totalling 14,879 tonnes of salt. This represented the largest portion of the total scheme salt discharge across all sectors. Ambient salinity (average daily EC) was higher than the 900µS/cm target threshold between September 2024 to January 2025, when flows were low. Average annual salinity in the upper sector for the period (869 µS/cm), was similar to the average across 2015–2025 (858 µS/cm). 

Lower sector: From the junction of the Hunter River and Glennies Creek to Singleton

Figure 5 shows the maximum daily salinity, minimum daily river flow and high flow salinity threshold in the lower sector for the 2024–25 period.

Figure 5: Daily average salinity and flow: Hunter River at Singleton for 2024–25

Significant inflows only occurred during the final three months of the 2024-25 financial year. Wollombi Brook produced some inflows during the May–June event. The highest observed peak flows were approximately 21,200 ML/d at Wollombi Brook gauge and 17,000 ML/d at Glennies Creek.

There was a total of 18 discharges in the lower sector, all in the fourth quarter, totalling 1,689 tonnes of discharged salt. Ambient salinity (maximum daily EC) was higher than the 900 µS/cm target threshold for most of the days between September 2024 to January 2025, when average daily flow was low. Average ambient salinity for the year (803 µS/cm) was lower than the previous year (1000 µS/cm) but higher than the longer term average for 2015–2025 (722 µS/cm). Higher flows corresponded with sharp salinity decreases to well below the 900µS/cm target threshold, permitting discharges during high and flood flow conditions.