About surface water modelling

How we use models

Our models simulate NSW river systems. They can be thought of as ‘large modelling infrastructure’.

Their main uses are to:

• inform government policies and planning
• evaluate climate risks
• monitor and report on how we meet our legal obligations under section 71 of the Commonwealth Water Act 2007 and our water sharing plans.

The climate of most NSW regions is drying, and climate risk is increasingly important to managing water. Models can be used to assess climate risk to NSW water supplies and infrastructure.

We are subject to various legal reporting requirements, including under the Water Management Act 2000. Water modelling also supports us in meeting these statutory reporting requirements.

Model reliability and variability

We take a best practice approach to modelling. We ensure our models are fit for purpose and produce reliable results by:

• applying our modelling principles
• sourcing appropriate data
• calibrating our models effectively
• reviewing our results.

Models don’t forecast behaviour over a specific future period, the way a weather forecast does. Rather, they simulate how the river system would have responded to climate and in the past. They are our best available estimate of how these complex systems interact and behave. As such, they help us understand how a system might behave if water were managed differently, or if different rules or decisions were applied.

We review input data and calibrate the models themselves to ensure our models represent river systems as faithfully as possible. All our models are independently peer reviewed and audited to ensure they are fit for their intended purpose.

Models are most helpful when we use them in a way that reflects their capabilities and limitations. Our guidelines help us ensure the models we build are generally fit for purpose and produce robust, reliable results.

Surface water modelling guidance

Our modellers follow a guidance framework that describes how we plan, build and maintain river system management models to ensure they are:

• consistent
• scientifically robust
• useful.

Our guidance is based on the extensive knowledge and experience of our modelling specialists and reflects many years of modelling practice. It covers all stages of planning, building, calibrating, reviewing and using a model.

The guidance is also informed by work we have done with the broader Australian water modelling community of practice.

Community of practice

Modelling is widely used in government, industry, academia and environmental work.

Our team actively engages with a wider community of practice. We have worked with CSIRO, the Murray Darling Basin Authority, and Queensland, ACT, Victorian and South Australian government modellers to develop modelling practice notes that help us ensure our work is:

• consistent
• transparent
• effective and efficient.

Learn more about the Australian modelling practice notes and how our community of practice shares knowledge.

Modelling New South Wales river systems

Modelling platform transition

Many of our models are more than 20 years old; they were developed on the IQQM hydrological modelling platform. We have committed to transitioning these models to Australia’s national hydrological modelling platform, eWater Source.

Source was collaboratively created by government, industry and researchers.

Many of our river system models have already been rebuilt using Source, and their quality and effectiveness independently peer reviewed.