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Engagement – February 2024

The topic for February 2024 webinar was on climate variability and change in water management in NSW.

Macintyre River.

Water Engagement Roundup

The questions and answers from the Water Engagement Roundup webinar recorded on Wednesday 21 February 2024 will be published shortly. The topic for this webinar was climate variability and change in water management.

Watch the webinar

Wednesday, 21 February 2024. This month's update was on the climate variability and change in water management.

Questions and answers

In response to climate change, how will you decide whether to reduce license entitlements to maintain environmental flows, or reduce reliability by leaving AA formulas as they are or making them more severe, or build infrastructure to improve supply reliability?

A. Assuming that “AA formulas” refers to the calculations underpinning Annual Allocation / Available Water Determination (AWD) announcements. Initially we will be undertaking the technical analysis to understand risk of future climate to inflows, AWDs, water security, and flows. On the basis of these changes and what they mean to water dependent sectors, we intend engage with stakeholders to make decisions on what changes if any we should make to our water planning arrangements. We need to recognise that these are important questions and will be worked through via both national processes and at a state level and regional level as part of the roll out of actions under the strategies.

Will the department be updating their water catchment models with NSW and Australian Regional Climate Modelling (NARCliM) 1.5 RCMs (or 2.0 when published, if ever) and providing those results to the NSW SEED platform. Have any sensitive assessments been completed for NARCliM 1.0 RCM's given potential concerns over cold bias results to historical data when undertaking a hindcasting assessment? 

A. We plan to continue to take the approach of using NARCliM (NSW and Australian Regional Climate Modelling) model outputs as a line of evidence of potential climate change by combining with our stochastic climate data sets. The variability characteristics including extremes captured in our stochastic data are likely to be the dominant risk factor for most parts of NSW for the near future, with the exception to this being the southern inland region.

The department is undertaking a detailed hydrologically based assessment of NARCliM results to better understand how these are best incorporated in our water models. There are no current plans to put projected climate change affected streamflows on SEED as there are a multitude of potential climate futures. However with the information on models and stochastic data sets currently uploaded to SEED, anyone accessing these could combine with climate projections of their choice to produce their own modelled outputs.

A. Regarding question 2, we are not aware of these assessments being undertaken. For our current iteration of regional water strategies, we combined the driest NARCliM 1.0 GCM/RCM results with our stochastic data as a stress test of water availability.

Is NSW Water engaging with Aboriginal knowledge holders to bring cultural knowledges into managing water under a changing climate e.g. through seasonal calendars etc?

A. This is included in our workplan, but we have not yet commenced work on this.

The NSW Government’s Coastal Drainage Policy is assuming a sea level rise of 1 metre, which would in turn see corresponding rises in river levels where there is tidal influence. Is the same assumption to be used in all the department’s climate related policy? Please provide the source of the scientific information used to arrive at this assumption.

A. The coastal drainage policy does not explicitly assume a 1 metre sea level rise. Rather it notes that coastal floodplain areas which are less than one metre above sea level already face difficulties draining effectively during the existing tidal cycles, and these difficulties will be exacerbated by sea level rise. There is a consultation webinar of the coastal drainage policy being held in March 2024 which would be useful to join one for those interested to ask some more questions. For more information visit Coastal Floodplain Drainage Project.

How will the updates on climate variability and water management affect planning for rain-dependent projects such as new dams?

A. The impacts of climate variability on water security for water dependent sectors was considered in most of our regional water strategies using the stochastic data in our water models. Where vulnerabilities were identified to water dependent outcomes, infrastructure and non-infrastructure options were identified and their costs and benefits assessed, including stress-testing with dry climate change projections from the NARCliM models.

Does NSW Government have any position which climate change/resilient scenario should consider for the future water infrastructure planning assess water security and existing system reliability?

A. This is an area of development. As part of the Regional Water Strategies (RWS) we used a bookending approach where we compared outcomes for current conditions and an extreme dry end scenario. But the RWS is designed to be a "first pass" assessment and detailed infrastructure assessments would still be required. Approaches were developed using this information in some assessments completed or underway. There is a whole of government working group (the Common Planning Assumptions Working Group) which is tasked with developing guidance on which climate scenario should be used - noting that this may change based on the lifecycle of the infrastructure or planning tool, and developments in climate science.

The Murray Valley Private Diverters seek explanations of reliability, water property rights, and security entitlements; an assessment of cumulative water policy changes and proposed further changes; impact on members ability to receive their water orders through climate policies that reduce General Security allocations, and explanation of how changes for 'modelled' climate policy will lead to water conservation in major storages and manage flood risks.

A. We have not completed an impacts assessment at this point. Some of these issues will be considered as part of the Murray Regional Water Strategy.

Will water sharing plans be revised so that annual water determinations are based on the most recent drought of record data?

A. Nearly all of the regulated river Water Sharing Plans include a requirement to review the assumptions underpinning the drought of record. Most of those water management decisions up until now have been based on the historic record and planning around one worst drought without really having a clear understanding of the level of risk of that occurring. The work we are commencing will use the new climate information to determine how we can make our AWD decision-making with a better understanding of the risk underpinning these decisions.

What is the level of currency and total time period of rainfall data used create models about water flows in our rivers and streams?

A. We used all available relevant climatic and hydrologic data in creating our models. Spatial coverage of observational rainfall stations was sufficient for river system scale modelling from the 1890s. We use this in our various calibrated water models to provide estimated flows back to this time. This approach has been in place for some time. The models are reasonably current, those used to assess diversion compliance are updated after the end of each water year, meaning these are current to end June 2023. For other water models the data is updated periodically and will be prioritised as and when the model is actively used in water planning.

Will the cultural value of water be considered?

A. Yes. It is not yet a significant part of the climate program workplan, but it is definitely something which is a key pillar of the NSW State Water Strategy and something that our department is committed to improving.

As part of the development of the suite of strategies under the NSW Water Strategy, the NSW Government is developing a state-wide Aboriginal water strategy. The strategy will identify ways of increasing water rights and ensuring that First Nations/Aboriginal people are empowered to contribute to water management and planning decisions.

What is the NSW policy to prioritise conservation of Ramsar sites in the face of prospective losses because of climate change and human disturbance?Is there a protocol for maintaining the required hydrological regime to conserve the Ramsar sites as climate change impacts increase?How is NSW monitoring the impacts of climate change plus human disturbance on the condition and integrity of the NSW Ramsar sites?

A. The Commonwealth Government is required to monitor and report to the Ramsar Convention Secretariat under Article 3.2 of the Ramsar Convention, if the ecological character of any Australian Ramsar wetland has changed. This is done through partner states including NSW. As such DCCEEW Biodiversity, Conservation and Science (BCS) group have a policy to follow the 'National guidance on notifying change in ecological character of Australia's Ramsar Wetlands (Article 3.2)'. BCS or the Commonwealth have commissioned ecological character descriptions (ECDs) for numerous NSW Ramsar sites. These ECDs provide observed condition at 'a given point in time.’ If a case for a change in ecological character is submitted and then accepted by the Ramsar secretariat, we then need to develop a response plan to mitigate these changes. For example, an Article 3.2 response strategy has been developed for the Macquarie Marshes.

ECDs assess hydrological changes as part of a broader condition assessment at ‘a given point in time.’ Climate change impacts on hydrology are identified as one of the many threats and modelled or citable climate models are used in the development of ECDs where available. The resulting response strategies are then focussed on restoring ecological character, which will typically include restoring aspects of, but for availability reasons not all of the natural flow regime.

The ECDs are one form of assessment that aid this process, as they rely on information from many past and current commonwealth and state environmental monitoring programs. The current commonwealth-funded monitoring, evaluation and research program (Flow-MER) and the Murray Darling Basin Authorities’ The Living Murray (TLM) program are using existing data and generating new data to inform environmental water and Ramsar site managers.

Is there a recognition that using long-term averages obscures the impact of increasing extreme weather events?

A. Yes. We have recognised for some time now that we need to consider all temporal aspects of water availability in understanding outcomes, including extreme droughts and floods - as referred to in presentation - that we see in our climate data sets and everything in between. The long-term average often quoted is a measure of the relative wetness or dryness of different climate periods, but is not directly used to determine water sharing arrangements.

Climate modelling --There is talk in scientific press that the warming of the oceans is making the existing climate models unreliable for future forecasting . Any comment?

A. The degree to which climate models currently represent atmospheric and oceanic conditions that determine rainfall is an area of climate science we and others think is important to understand to inform us how reliable different models are. Climate science is evolving, and findings such as this will inform update and evaluations of climate models, and how these modelled projections can be used is an ongoing body of work, in the department, as well as nationally and globally.

We are currently examining how we can use the most up to date climate models for NSW (NARCliM 2.0). The driving global climate models used by NARCliM are a subset of all available climate models used in the IPCC assessments. This subset was selected after a rigorous assessment. However, as we know that climate modelling is a continually evolving our focus is on applying methods that are useful regardless of which climate model(s) we use.

That Orana data would suggest an increase in mean precipitation in every season, with higher winter uncertainty?

A. That graph is sourced from climate snapshots that what is now the Biodiversity Conservation and Science division put out a number of years ago. It uses a subset of older  climate projections that what is available today. The graph was used for illustrative purposes.

While the graph does show that the median climate models show a slight increase in annual rainfall, It also shows the wide spread of modelled rainfall outcomes, ranging from significantly wetter to significantly drier. This demonstrates how important it is that we take a risk-based approach to decision making, as we cannot rely on the median modelled outcome being the one which occurs.

That is why we are working to build a framework which can deal with the range of variability from the range of climate models.

What approach is the agency recommending to government after all these data are assessed? Considering the variability and risk will the agency be recommending (a) a conservative or precautionary approach to water use planning (b) a moderate or "two bob each way" approach or (c) a high risk or aggressive approach?

A. We are currently working on the technical analytical aspects of the overall approach, and outcomes from that analysis will inform other assessments and engagements we need to have before we are in a position to make recommendations.

If it is already certain that evaporation is going to be a key risk to water availability what planning/action is occurring to reduce evaporation, ie revegetation of riparian zones on rivers, streams and drainage lines and planting in riparian zones but crucial to fence off those areas to stop stock destruction of same.

The impacts of evaporation are significant in terms of water availability across the whole of the catchment, not just confined to riparian zones. However, there are a number of other recognised benefits to improved riparian zone management, including ecological outcomes, such as increased habitat and shading.

These benefits have been recognised in a number of the Regional Water Strategies developed across NSW, with actions identified across government to achieve catchment management outcomes. These include:

  • A Northern Rivers Watershed Initiative has been established through the Northern Rivers Joint Organisation of Councils to improve water security and catchment health. The initiative will ensure a joined-up approach to catchment management modelling and natural flood mitigation to improve riverine health and reduce flood risk.
  • The department will continue to work with Local Land Services to implement the Riverbank Rehabilitation Project at critical sites across the state and provide guidance to landholders on best practice management to support the regeneration and protection of waterways and estuaries.

A further initiative to minimise the impacts of livestock on riparian areas to improve water quality and native fish habitat is the NSW Fencing Northern Basin Riverbanks Program. The program led by Local Land Services, provided landholders along priority reaches in the northern Murray-Darling basin with funding assistance to undertake on-ground projects. In total, landholders signed up to construct 260 kilometres of fencing to protect around 13,000 hectares of riparian land and undertake around 2,000 hectares of weed and erosion control works.

Is the 'balance' under consideration a trade-off between adaptive management and security for water users?

A. We are looking at striking a balance between security for water users such as towns and environment as well as the ongoing viability of our industrial and irrigation users. Adaptive management is one of the tools we will be using to try and make sure we find the right balance.

For the inland rivers, how often are the historic drought records (as measured by low dam levels, for example) lower, that is more extreme than the modelled/expected drought dam levels? ie for an expected 1 in 20-year drought, for an expected 1 in 50-year drought?

A. The key benefit of using the different sources of climate information (e.g. paleo, stochastic, and climate models) is that we can do these sorts of calculations. Within the Paleoclimate informed stochastic datasets, it is likely that these extreme events do occur more frequently than indicated in instrumental records. There are two main reasons for this:

  • The paleostochastic data represents the range of variability captured within the paleoclimate evidence – and this shows that there were previous droughts which were more severe than have occurred during the recorded data,
  • The paleostochastic data provides a 10,000-year dataset compared to only 130 years of historic data. As a result, there is an increased chance that we have captured the range of extremes within this longer period.

Some examples of this can be seen within the Regional Water Strategies.

I do not know why people only go back to the 1890's as there are records in NSW that go back further. e.g. NSW Sydney Observatory Hill Station 66062 commenced in 1858.

While longer records do exist in a small number of locations in NSW, we require data which provides adequate coverage across all of NSW.  The spatial coverage of rainfall stations was not comprehensive prior to around 1890. We use rainfall from the SILO gridded climate dataset, providing data from 1890 throughout the whole of NSW.

Will the Chief Scientist review the options paper we can expect to see by 2026? 

We have been committed all the way through to making sure we have rigorous science and use robust decision-making tools. We engaged an independent expert panel led by the Office of Chief Scientist and Engineer in the early stages of this work and have been endeavouring to follow recommendations from their report to continue to improve our work. We have advocated for and supported expert advice for basin-wide hydroclimate approaches in the Murray Darling Basin and will be looking at a similar independent expert approach to make sure that our work continues to be scientifically rigorous and defensible.