The future of stormwater at Ginninderra
The population of the ACT is projected to grow to half a million people by 2033.
With this urban growth and the changing climate we can expect an increased demand for water and the generation of more stormwater and sewage.
CSIRO is committed to sustainable urban water management and undertaking research that will help reduce the demand for potable water supply in our cities. This includes research on various aspects of reducing water use and making better use of available rainfall, stored and potable water and waste water streams.
“Urban stormwater is a relatively untapped resource that could help Canberra meet its future water supply requirements,” said CSIRO Researcher Dr Declan Page
CSIRO examined the feasibility of a range of stormwater harvesting and irrigation options in Canberra during 2007 to 2009, working with the ACT and Commonwealth Government’s on Phase 1 of the Canberra Integrated Urban Waterways Project.
In addition to reducing demand for potable water, stormwater harvesting has the potential to provide stormwater quality improvements, flood mitigation, urban habitat outcomes, and has the potential to improve the aesthetics and the recreation value of urban parks.
The stormwater harvesting options that were considered included; use of existing lakes and ponds, the construction of new ponds, through to options that involved combining stormwater with water stored in aquifers or with reclaimed water.
This CSIRO research was used by the ACT Government to support the feasibility through to detailed design and construction of three pilot stormwater harvesting and reticulation projects, namely Inner North Canberra, Weston Creek and Tuggeranong.
The Inner North Stormwater Reticulation Network in the Sullivan’s Creek Catchment is Canberra’s first neighbourhood-scale stormwater harvesting and managed aquifer recharge system. Urban stormwater is captured and treated in constructed wetlands and then pumped though a reticulation network for irrigation of urban green spaces.
The ACT Government is currently trialling managed aquifer recharge as part of this Inner North scheme, which involves the injection of stormwater into a bore, where it is stored in underground aquifers and retrieved when required during peak irrigation.
CSIRO has considerable expertise in this innovative urban water technology, having recently completed a large study on Managed Aquifer Recharge and Stormwater Use Options (MARSUO) commissioned by the Goyder Institute for Water Research.
The aim of the study was to provide water managers and the community with the data needed to make informed decisions on stormwater harvesting and storage.
“Stormwater could be treated to a drinking water quality and not just used for open space, third pipe or industrial uses. The costs of doing this, however, are similar to the costs of conventional potable water supply,” said co-author of the study Dr Page
“Nonetheless, the MARSUO study shows that water quality/safety issues can be effectively managed in line with the National Water Quality Management Strategy”.
It is early days to consider stormwater options in the Ginninderra project, as we await the outcome of the land reclassification decision under Draft Amendment 86 of the National Capital Plan, which is required to consider the potential future urban development of the site.
Having said that, Ginninderra Creek and Halls Creek and their associated riparian areas are significant features of the Ginninderra site and the broader landscape.
“Ensuring the retention of adequate space for stormwater capture and treatment, providing green corridors along water courses, and implementing water sensitive urban design throughout the site, is all of paramount importance”, said Dr Page.
CSIRO researchers are currently investigating the water resource potential at the Ginninderra site and the types of stormwater use options. As noted in a previous update, one of these future uses will likely include the provision of water to support the cooling benefits of healthy vegetation to combat the Urban Heat Island effect.
As the project progresses, CSIRO looks forward to interacting with key stakeholders such as the ACT Government, Icon Water, and Ginninderra Catchment Group, as well as neighbouring communities and businesses, to discuss stormwater options.
Beating the heat at Ginninderra
We’ve all experienced the cool relief of seeking respite from a hot day under a shady tree. Recent studies have shown that tree cover plays a large part in combating the urban heat island effect.
Canberra is hot and getting hotter. Temperatures in the ACT have been increasing since about 1950.
Canberra sweltered though 10 consecutive days of 30-degree plus temperatures in early March, providing our hottest start to autumn on record.
This warming trend is set to continue, with recent projections of Canberra’s future climate indicating that temperatures are likely to rise further, resulting in more hot days and fewer cold nights.
This is exacerbated by the Urban Heat Island effect, where cities tend to trap and store heat during the day, staying hotter for longer than the surrounding countryside during the night.
To understand patterns of urban heat across Canberra, researchers in CSIRO Land & Water have used satellite thermal imagery to estimate land surface temperatures and map their distribution.
We recently tested this at Ginninderra Field Station, which yielded some very interesting results.
Dr Matt Beaty, a Senior Experimental Scientist in CSIRO Land & Water said, “As with other cities around Australia, there is a strong relationship between vegetation and land surface temperatures.”
“Newer suburbs, and industrial areas in Canberra with little vegetation cover, are typically much hotter during summer than older suburbs with established tree cover providing dense shade.”
The availability of water is also important. Not just to support healthy vegetation, but to drive the processes of evaporation and transpiration that provide cooling benefits in addition to tree shade.
CSIRO’s urban heat mapping for Canberra has been featured by the ACT Government in their draft ACT Climate Change Adaptation Strategy which is open for public consultation until 3 April 2016.
“There is a lot to be learnt from this urban heat mapping work that is relevant to the proposed urban development of the Ginninderra site and how we adapt our cities to climate change,” said Dr Beaty.
CSIRO heat mapping for the northern part of Canberra (shown below) identifies that during a hot summer day established suburbs are cooler than the Ginninderra site and surrounding countryside.
“This is due to the influence of suburban gardens and associated irrigation, which tends to result in cooler land surfaces than bare cultivated soils and dry sheep paddocks.”
The coolest parts of the Ginninderra site are the waterways and areas with existing tree cover.
“What this means is that large trees, irrigated grass and water will need to be a key feature of the design of any potential future urban development to combat the Urban Heat Island effect through the provision of shade and to drive the cooling benefits of evapotranspiration,” Beaty said.
Based on site investigations so far, approximately 150 hectares of the land on the Ginninderra site is unable to be developed due to its topography, heritage and ecological values, and is envisaged to form an open space network of connected recreational and conservation areas. This idea of ‘fingers of green’ through the site was reflected in the draft concept presented to the community last year.
But it’s not all about trees, other strategies for adapting our cities to increasing urban heat include the use of light-coloured construction materials in our buildings and paved surfaces. Light coloured surfaces reflect incoming solar radiation, reducing the amount of heat that is trapped in our cities.
Jacqui Meyers, another Senior Experimental Scientist in CSIRO Land & Water has undertaken research on the impact of climate change on the heating and cooling energy costs of a typical Canberra home. This research is also cited in the ACT Government’s draft ACT Climate Change Adaptation Strategy.
“The energy required to heat a typical Canberra home in 2070 may be one-third lower, but energy for cooling could more than double,” Myers said.
“An integrated response to urban heat is required, which includes a focus on climate-wise buildings, planning provisions that provide space for trees to shade buildings and pedestrians, and open space networks that support healthy vegetation and waterways to deliver further cooling benefits.”
Overall, there are many opportunities for science to inform the planning and design of the proposed urban development of the Ginninderra site. More tree cover is good for addressing the urban heat island effect, but would also provide many other social and economic benefits.