Performance in each sector

Hunter River Salinity Trading Scheme Performance Report 2023–24.

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. Figure 6 shows that background salinity was relatively high between November 2022 and early 2024, before it started to trend downwards into the normal range.

Upper sector: Hunter River upstream of Denman

There were no significant inflows from the upper sector tributaries into the Hunter River. Flow at Denman was below 500ML/day throughout the period until environmental water was released from Glenbawn Dam in late May 2024. There were 4 discharge opportunities in the upper sector during the first week of June.

Figure 7 shows the average salinity and average river flow in the upper sector for the 2023–24 period and the salinity targets during high flow and flood flow. No flood flows were recorded in the 2023-24 period.

There were no industry discharges in the upper sector during the period. Natural ambient salinity in the upper sector is lower than the middle and lower sector, with the upper sector EC target 600µS/cm. Average annual salinity in the upper sector for the period was 707µS/cm, while the average across 2016–2022 was 570µS/cm.

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

Figure 8 shows the average salinity and average river flow in the middle sector for the 2023–24 period.

Only 5 discharges over 2 days occurred in the middle sector for the period. Ambient salinity (average daily EC) was high, and above the 900µS/cm discharge threshold, when average daily flow was low. Salinity decreased as flow increased, with EC dropping well below 900µS/cm when the river was in high flow, and discharges were permitted. This demonstrates the scheme is performing as intended.

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

Figure 9 shows the average salinity and average river flow in the lower sector for the 2023–24 period.

A total of 12 discharges occurred in the lower sector for the entire period, all in the fourth quarter. Ambient salinity (average daily EC) was higher than the 900 µS/cm target threshold for much of the period, when average daily flow was low. Average ambient salinity for the year (1000µS/cm) was also higher compared to the 2016–2022 average of 638 µS/cm. Higher flows corresponded with sharp salinity decreases, permitting discharges during flood flow conditions, when salinity was well below the 900µS/cm target threshold.