Sydney drinking water catchment future scenarios for 2040 and 2060

WaterNSW is already doing just that, by using historical rates of land use change to construct multiple narrative scenarios describing alternate futures in 2040 and 2060.

These exercises of science-based imagination, explored via spatial modelling, tangibly illustrate how changes in land use may impact the catchments that protect the quality and quantity of water essential to the 5 million people of Greater Sydney.

“This project extends on typical modelling approaches by incorporating narratives to drive and enhance creative and critical thinking necessary to address the complex challenges of the future as we continue to provide an essential resource,” WaterNSW Executive Manager Strategy & Performance, Fiona Smith, said.

Developed in partnership with UTS Institute for Sustainable Futures, the 2040 and 2060 future catchment scenarios are helping WaterNSW understand and plan now, for future megatrends and local drivers, that may create potential risks or opportunities for water supply and catchment health.

“Geographic Information System (GIS) projections created from each scenario are designed to be used with catchment models to understand how water quality in Sydney's drinking water reservoirs could change in the future, even under conditions outside of our historical experience,” Fiona said.

“This approach can be used to identify particular risks, opportunities or gaps in our understanding to focus further attention on, before significant impacts to catchment health or water quality become apparent.

“Scenarios like these are a valuable tool our scientists and water industry experts can use to engage with the long-term future whilst acknowledging inherent uncertainty. Such creative visualistion enables preparedness and resilience several decades into the future.

“Sustainability is one of the themes of Science Week being celebrated across Australia this week, and a great time to recognise the benefits of this kind of collaboration between universities and the water industry.  By combining descriptive narratives with robust modelling the approach used here can set the state for proactive planning and decision-making to ensure ongoing resilience in the water industry.

“We asked UTS to work with us to develop this set of alternate future catchment scenarios that may arise from the identified trends using input from WaterNSW stakeholder,” Fiona said.

WaterNSW is required to undertake research on catchments generally, and in particular on the health of declared catchment areas that protect water quality in the Greater Sydney drinking water catchment.

The WaterNSW science program has two core research themes:

• Catchment resilience – understanding how catchment health and water quality work together to ensure a safe drinking water supply, and ensuring we have the knowledge to best manage and protect the catchments in a changing climate.
• Integrated water management – understanding how changes to the environment and supply configuration impact water quality and quantity, and how we can improve water quantity without compromising water quality.

Scenarios from Catchment Futures Scenario Project by WaterNSW and UTS Institute for Sustainable Futures.

Baseline Scenario

This scenario describes and models what could be expected if past trends continued into the future. Historical land use and land cover trends (1988-2019) were projected forwards to 2040 and 2060. This scenario also considered current population projections.

Alternate Future Scenarios

The alternate future scenarios described below are a series of narratives informed by global and regional trends and drivers identified by examining existing literature and undertaking stakeholder workshops with expertise from water utilities, academia, and government departments. The narratives are storylines designed to imaginatively capture possible futures and were used to manipulate the baseline model to provide a tangible and interactive representation of what these could look like. Whilst WaterNSW doesn’t expect any of these scenarios to eventuate exactly as described, they are useful tools for considering previously unexperienced conditions as we plan for an increasingly uncertain future.

Scenario 1 – Enhanced catchment management

There is increased investment in catchment management as a key strategy for providing safe drinking water to Greater Sydney. The urban footprint is the same as the baseline scenario, with increasing population living in those areas. Communities are highly engaged and expect catchment health to be valued, protected and effectively managed by government. Under this scenario there would be a decrease in disturbed land, increased reforestation, and improved management of forested areas.

Scenario 2 - Living life in green, blue and grey

A new high-speed rail link from Sydney to Canberra creates major new population centres in Goulburn and the Southern Highlands that are cool, green and liveable with integrated water management principles. Urban expansion in south-west Sydney slows as cheaper and more liveable homes are available a 30 minute train ride from Sydney. Under this scenario there would be a decrease in disturbed land, increased reforestation, and improved management of forested areas. However, expanding urban areas lead to decreases in grazing areas, and populations must rely on more intensive food productions in urban landscapes.

Scenario 3 – Carbon positive catchments

Renewable energy and carbon forestry become dominant industries in the catchment, and are a key driver for increased catchment enhancement and restoration measures. Examples include forest regeneration, green energy, transmission and storage (pumped hydro, wind and solar farms). This scenario would see expanded and enhanced forested areas, decreases in grazing land, minor increases in disturbed land with installation of renewable energy infrastructure. The urban footprint remains the same as in the baseline scenario.

Scenario 4 - Mega supply for a mega city

Increased population growth, higher than in the baseline model, creates dense mega-cities bordering the catchment boundaries in Sydney’s south and west, Wollongong and Nowra. To manage increased pressure on catchment health and water security, increased focus is on both catchment management and alternate water sources including desalination and introducing potable reuse. This scenario imagines a future where there is an increase in the urban footprint and increase in disturbed land due to intensive agriculture needed to meet the demands of the rapidly growing population.

Scenario 5 – Full reliance on treatment

Catchment areas have faced prolonged droughts and fires resulting in poor water quality. Enhanced centralised treatment and potable reuse are key strategies for providing safe drinking water to Greater Sydney.  Population growth rates remain the same but development controls in the catchment are relaxed, and new development is not water sensitive and forested areas are reduced for urban expansion. Grazing and intensive agricultural activity, extractive industry, and recreation in the catchment also increase, with more land transitioning to grazing and disturbed

Scenario 6 – Extreme climate impacts

Government and community are in a constant state of response to rolling climate emergencies impacting the catchment. The costs of responding are high, and an emergency mitigation is the dominant activity. With continued ecosystem destruction, catchment management becomes a lower priority. Large swathes of forested and grassland areas transition to disturbed land due to climate impacts, and people relocate from small holdings and Western Sydney to Southern Highlands urban centres to escape fires and extreme heat.