Gwydir Valley floodplain harvesting and water sharing licence rules

The [link to new Licensing floodplain harvesting page] NSW Floodplain Harvesting Policy[/link] requires that individual entitlements in regulated river systems are informed by a capability assessment that considers the works used for floodplain harvesting and the opportunity to access floodplain flows based on location and climatic variability. This capability assessment is undertaken through river system models. The following reports were updated in May 2022, addressing some minor corrections and clarifications to reports previously published in February 2022.

• Building the river system model for the Gwydir Valley regulated river system–May 2022 (PDF, 14.6 MB) describes the development of the Gwydir Valley river system model. The model was developed using multiple lines of evidence and best available industry data. The report provides evidence and assessments to demonstrate that the model is fit for purpose.
• Floodplain Harvesting Entitlements for Gwydir Regulated River System–May 2022 (PDF, 974 KB): Model scenarios report describes how the model of the Gwydir Valley was used to estimate the baseline diversion limit, and to subsequently estimate individual floodplain harvesting entitlements.

Previous versions of these modelling reports were published in February 2021 and February 2022. The previous versions are available below:

• Building the river system model for the Gwydir Valley regulated river system–February 2022 (PDF 14.6 MB)
• Building the river system model for the Gwydir Valley regulated river system–February 2021 (PDF, 14.6 MB)
• Floodplain Harvesting Entitlements for Gwydir Regulated River System: Model Scenarios Report–February 2022 (PDF, 909 KB)
• Floodplain Harvesting Entitlements for Gwydir Regulated River System: Model Scenarios Report–February 2021 (PDF, 909 KB)

These reports were independently peer-reviewed in January-February 2021, and subsequent reports have incorporated ongoing improvements and refinements, including feedback from the independent review: - Gwydir reports review–summary, January 2021 (PDF, 168 KB).

Harvesting of water from floodplains reduces the volume, frequency and duration of floods and can change the timing of flood events, impacting the health of floodplains and downstream waterways. The NSW Floodplain Harvesting Policy will provide a more sustainable level of water diversions from the floodplain.

Hydrological metrics for native fish, floodplain native vegetation, waterbirds, key ecosystem functions and wetlands were modelled for two scenarios. Implementation of the policy is predicted to improve the number of flow days, frequency, and timing of floods for native fish, waterbirds, and floodplain vegetation.

Environmental outcomes of implementing the Floodplain Harvesting Policy: Gwydir report (PDF, 12 MB) provides a detailed assessment of the likely benefits for the environment of implementing the policy in the Gwydir Valley.

A summary of the environmental outcomes predicted for the Border Rivers, Gwydir and Macquarie valleys is available below.

• Summary of the predicted environmental outcomes of implementing the policy (PDF, 195.54 KB)

The NSW Floodplain Harvesting Policy will restrict the volume of water that can be taken from the floodplain providing gains to the system through foregone diversion.

Any gains in upstream systems such as the Gwydir Valley will translate into the downstream with additional volumes originating in each of the Barwon-Darling tributary valleys contributing to connectivity between the broader northern Basin system and provision of increased flows towards Menindee Lakes and into the Murray River.

Modelled downstream effects of licensing floodplain harvesting in the Gwydir Valley report (PDF, 5.2 MB) quantifies the potential downstream impacts of these increased flows. This report includes work completed for the NSW Border Rivers and the Gwydir valleys.

The proposed rainfall runoff exemption can potentially impact floodplain harvesting modelling in the NSW Gwydir Valley. The department has proposed a regulation to exempt rainfall runoff that is collected in a tailwater return drain from requiring a water access licence and a water supply works approval. The successful commencement of this exemption will impact floodplain harvesting modelling in the NSW Gwydir Valley. This report clarifies the scale of this potential impact on licence shares, the environment, and downstream outcomes.

• Rainfall Runoff Exemption Supplementary Report – Gwydir Valley (PDF, 1026.57 KB)

The process for determining entitlements of floodplain harvesting (unregulated river) access licences and unregulated river access licences is the same. Accordingly, it is proposed to apply the same rules to floodplain harvesting (unregulated river) access licences as currently exist for unregulated river access licences in the relevant water source and/or management zone, where appropriate.