Hunter River Salinity Trading Scheme 2023-24 Performance Report
In the 2023–24 financial year there were few large rainfall events, with no discharge opportunities at all from July 2023 to March 2024.
Summary
Salinity stayed within guidelines during periods of industry discharge to the Hunter River in the 2023–24 financial year.
Background salinity was at prolonged high levels, before declining in the March–June 2024 period.
Drier weather may have led to less need for discharges, with Scheme participants using a lower percentage of discharge opportunities than in previous years.
With the exception of Hunter Valley Operations, participants managed their onsite water within the regulatory framework, only discharging during available opportunities.
The EPA acknowledges the inherent challenges for industry regarding saline water management and will be performing a review of the Hunter River Salinity Trading Scheme Regulation in 2026. The review will include an investigation of the Scheme’s operations under extreme weather events to ensure effective on-going management of salinity in the Hunter River, and will include reviewing the river sector (upper, middle, lower) salinity target levels.
This report covers the financial year period from 1 July 2023 to 30 June 2024. The report captures the Hunter River’s conditions throughout the year, the opportunities for industry discharges, those opportunities which were used and the salinity of the river during and outside of discharge opportunities.
WaterNSW are the Scheme’s Services Coordinator – the operator of the Scheme’s water model and telemetry network. Read WaterNSW’s 2023-24 Annual Report.
In the 2023–24 financial year there were few large rainfall events, with no discharge opportunities at all for the first three quarters from July 2023 to March 2024. There were only 13 days representing 23 discharge opportunities, in April to June 2024, where industry was allowed to discharge to the Hunter River over the three river sectors.
The low river flow and high salinity that was seen in the Hunter River from January to June 2023 continued through to February 2024. The Hunter River is known for comparatively high natural salinity but between July 2023 and February 2024 the salinity, specifically in the middle and lower sectors, was consistently higher than recorded over the past 10 years (see Figure 6).
Of note for Scheme management, however, the salinity levels during HRSTS discharge periods, when there is an influx of fresh rainwater, stayed well below the salinity targets (see figures 7-9).
In the 2023–24 period the communications hardware at each of the WaterNSW river monitoring gauges was upgraded by the Service Coordinator (WaterNSW) to ensure the gauges stayed capable of communicating via the incoming 5G network. The rollout took place in April and June 2024. Further detail is provided on the Maintenance of the gauging/modem network webpage.
Finally, in December 2024 a penalty notice was issued for breach of HRSTS licence conditions in June 2024 – a discharge of saline water from an unmonitored discharge point at the Hunter Valley Operations mine.
Scheme performance in 2023–24
There were 17 Scheme participants during the 2023–24 financial year. During this time, 5 participants discharged, 12 did not discharge, one of which did not hold a discharge licence (cannot discharge). Table 1 below shows a breakdown of the participants and their discharge status.
Table 1: Hunter River Salinity Trading Scheme participants 2023–24
| Sector | Participant | Facility Name/ Discharge Location | Status |
|---|---|---|---|
| Upper | AQC Dartbrook Management Pty Ltd | Dartbrook Coal Mine | Discharger (inactive) |
| Upper | Hunter Valley Energy Coal Pty Ltd | Mount Arthur Coal | Discharger (inactive) |
| Upper | Bengalla Mining Company Pty Ltd | Bengalla Mine | Discharger (inactive) |
| Upper | Mangoola Coal Operations Pty Ltd | Mangoola Coal Operations | Discharger (inactive) |
| Upper | Mach Energy Australia Pty Ltd | Mount Pleasant Operation | Discharger (inactive) |
| Middle | HV Operations Pty Ltd | Hunter Valley Operations (Parnells Dam) | Discharger (inactive) |
| Middle | HV Operations Pty Ltd | Hunter Valley Operations (Dam 11N) | Discharger (inactive) |
| Middle | Liddell Coal Operations Pty Ltd | Liddell Coal Operations | Discharger (active) |
| Middle | AGL Macquarie Pty Ltd | Bayswater Power Station | Discharger (active) |
| Middle | Mt Owen Pty Ltd | Mount Owen Mine | Non-discharger |
| Middle | Ravensworth Operations Pty Ltd | Ravensworth Mining Complex | Discharger (inactive) |
| Lower | HV Operations Pty Ltd | Hunter Valley Operations (Lake James) | Discharger (active) |
| Lower | Wambo Coal Pty Ltd | Wambo Coal | Discharger (active) |
| Lower | Verdant Earth Technologies Ltd | Redbank Power Station | Discharger (inactive) |
| Lower | Bulga Coal Management Pty Ltd | Bulga Coal Complex | Discharger (inactive) |
| Lower | Warkworth Mining Ltd | Warkworth Coal Mine | Discharger (inactive) |
| Lower | Mount Thorley Operations Pty Ltd | Mount Thorley Operations | Discharger (active) |
During July 2023 to June 2024, the Hunter River Catchment received between 400–900mm observed rainfall, which fell unevenly across the catchment. While this volume of rainfall is categorised as average compared to historical data, few individual rainfall events were large enough to trigger an HRSTS river register (discharge opportunity). There were 13 HRSTS discharge events/opportunities for the period. The lower sector had opportunity to discharge for all 13 events. The Middle sector had opportunity in 6 of the 13 events and the upper sector had opportunity to discharge in 6 of the 13 events.
Two of these were reissued, both times to increase the total salt discharge allowed due to higher rainfall than initially expected. Participants used 11 of these opportunities, with 17 individual discharges occurring. A total of five Scheme participants discharged within the financial year.
Table 2 below shows the breakdown of discharge opportunities and events per sector.
Table 2: Breakdown of discharge opportunities and events in 2023-24
Note: includes total number of times a sector credit factor of lower than 0.7 was applied to restrict discharge
| Sector | Opportunities | Opportunities taken | % of Opportunities Taken | Discharge events across opportunities | Participants with active discharge points | Sector Credit Factor (<1.0) applied |
|---|---|---|---|---|---|---|
| Upper | 4 | 0 | 0% | 0 | 0 | 1 |
| Middle | 6 | 3 | 50% | 5 | 2 | 1 |
| Lower | 13 | 8 | 62% | 12 | 3 | 0 |
| Total | 23 | 11 | - | 17 | 5 | 2 |
Sector credit factor
A sector credit factor less than 1 is applied in instances where the use of all credits would result in an exceedance of the salinity target for any sectors (during a register). A reduced sector credit factor (<1) moderates the salt load discharged per credit held by a participant and keep the sector’s salt load below sector EC targets. In 2023–24, there were 2 occasions where the sector credit factor was <1; once in the upper sector (being 0.33) and once in the middle sector (being 0.84).