Cities as water supply catchments
A research proposal that aims to harness the potential of stormwater to overcome water shortages, reduce urban temperatures, and improve the landscape and liveability of Australian cities
THE CHALLENGE FOR AUSTRALIAN CITIES
Figure 1: Challenges for Australian cities
Current centralised solutions to urban water management, whilst fundamental to the development of our cities to date, cannot solely provide the multiple benefits required for the future needs of our cities. We must find new, more integrated solutions that can address the range of climate change and related problems, by delivering simultaneous benefits for water resources, urban micro‑climates and landscapes, aquatic ecosystems, and the social framework that underpins them.
The vision of Water Sensitive Cities (WSC) is becoming increasingly accepted as the way forward. The philosophy of the WSC is to enable a hybrid of decentralised and centralised water management solutions that ensure resilience to both water-poor and water-abundant futures and deliver multiple benefits to people and the environment. However, WSC is still very much in its infancy and, if we are to advance its adoption, we must find ways of combining existing centralised water infrastructure with new, decentralised systems at a range of scales; for households, streetscapes, and neighbourhoods.
Of the range of solutions available, harvesting of stormwater in the urban landscape offers great potential. However, this potential has not been tapped due to widely perceived difficulties in its implementation, despite its fundamental role in the total water cycle (Radcliffe, 2003). Stormwater harvesting systems could be fully integrated into the urban landscape (e.g., Figure 2 illustrates several types of systems that could be employed) to deliver a wide range of benefits.
Figure 2: Street trees that collect and treat runoff from Bourke St, Melbourne (left), the rain-garden in Victoria Park, Sydney (middle) and Lynbrook Estate stormwater wetland, Melbourne (right).
Stormwater harvesting is essential to the realisation of Water Sensitive Cities, because:
o Urban stormwater is a large source of water, generated close to where it is needed. For example, the amount of stormwater discharged annually in Melbourne is approximately the same as the entire annual water demand of the city, and it is even greater in Brisbane, exceeding demand by around 50% (Figure 3, PMSEIC, 2007);
Figure 3: Urban water use and discharges, PMSEIC, 2007.
o Uncontrolled stormwater runoff from urban areas degrades creeks and waterways. The large amounts of impervious areas in cities results in excessive flows into waterways, causing erosion and pollution (Hatt et al., 2004). Stormwater harvesting can protect and enhance the health of urban streams by restoring flows and water quality back towards the pre-developed level. It is the only water source whose use will benefit the environment, rather than degrade it (Fletcher et al., 2007);
o Vegetated stormwater treatment facilities may improve the urban micro-climate and threrefore public health. Stormwater harvesting using natural vegetated systems such as wetlands and rain-gardens has an important role in reducing the urban heat island effect. By maintaining water in the landscape, local temperatures are decreased, reducing heat extremes. Unlike many technologies, passive cooling is utilised, thus not contributing to greenhouse gas production;
o Stormwater harvesting using green infrastructure enhances social amenity and is likely to be publicly acceptable. Increasing vegetation and “green landscapes” improves the social amenity of cities (Figure 2). Acceptance of stormwater harvesting is also much greater than it is for wastewater reuse (Brown and Keath, 2007); and
o Stormwater harvesting systems can function with very low energy use. Stormwater harvesting via a range of passive treatment and distribution methods based on biomimicry has much lower energy requirements than many other water treatment and supply solutions.
So why aren’t we harvesting stormwater?
Unlike the traditional centralised water supply systems, which have benefited from over two centuries of dedicated research and development, urban stormwater harvesting systems are relatively recent inventions. A number of important knowledge gaps are further impeding the widespread adoption of these systems:
o A lack of sustainable technologies. There is currently a lack of cost-effective technologies that can harvest stormwater at a range of scales, from household to regional, for both potable and non-potable use;
o Implications for cities from climate change. Although water harvesting systems must be robust to climate variability, we currently do not have methods for assessment of impacts of climate change on their design and performance;
o Likely benefits on urban micro-climate. The landscape benefits of large scale implementation of harvesting technologies (Figure 2), as well the benefits of urban irrigation on urban micro-climate, are as-yet unquantified;
o Likely benefits for receiving water ecology. Guidance on appropriate levels of harvesting with respect to maintaining and improving stream health in both existing and new developments, is required;
o Human health risks. Our knowledge of the public health risks of using harvesting stormwater is minimal, creating an uncertainty that impedes its adoption;
o Economics. The value of stormwater harvesting systems as multi-purpose assets needs to be assessed in the context of climate change and future general economic trends. There needs to be a clear business case made for stormwater harvesting, which considers externalities; and
o Society and Institutions. The role of institutional and social context in facilitating the widespread application of decentralised stormwater harvesting in Australian cities needs to be better understood.
Solving these individual impediments will not be enough; an inter-disciplinary approach is required if integrated and sustainable solutions are to be delivered.
WHAT WE AIM TO DELIVER
Our research programme aims to harness the potential of stormwater to overcome water shortages, reduce urban heat island effects, and improve the landscape and liveability of Australian cities. We propose to develop integrated stormwater harvesting solutions as part of realising Water Sensitive Cities, with the main attributes as outlined in Figure 4.
Figure 4: The main attributes of stormwater harvesting solutions
The key deliverables of the proposed projects are listed below:
1. Novel and sustainable stormwater harvesting technologies, building on proven decentralised Water Sensitive Urban Design concepts, that will be able to provide both potable and non-potable water for a range of urban development scales (households, streetscapes, and neighbourhoods);
2. Methodologies for assessing rainfall patterns in localised urban environments under a changing climate to inform the development, adoption, and operation of stormwater harvesting solutions;
3. Assessment of the micro-climatic and liveability advantages of stormwater harvesting solutions in comparison to schemes assessing other alternative sources of water (e.g. desalination, recycling sewage etc). The focus will be on wide adoption of vegetated treatment systems, implemented throughout the urban landscape, that may result in the localised improvement of human thermal comfort;
4. Identification of appropriate hydrologic indicators which could be used to set performance objectives or operating rules for stormwater harvesting, and give confidence that stormwater harvesting will result in a net improvement in the health of aquatic ecosystems;
5. Guidance on how to implement and operate stormwater harvesting systems to meet the required health and safety standards for water use (both potable and non-potable);
6. A template of new governance and policy mechanisms to expedite the practical application of stormwater harvesting technologies to industry and the community;
7. A framework for economic valuation of stormwater harvesting solutions, as multi-purpose urban assets, for current and future economic contexts of Australian cities; and
8. Demonstrated application of the systems at three scales, household, streetscape, and neighbourhood, as well as their integration into the urban form.
The project will consist of eight highly integrated projects, as illustrated in Figure 5.
Figure 5: The main project of the research program
P1: Sustainable Technologies. Stormwater harvesting technologies, which are decentralised and often space-constrained, will build on the proven concepts of Water Sensitive Urban Design (WSUD). A suite of solutions will be developed that will be able to deliver both potable and non-potable water for three different urban scales: household, streetscape and neighbourhood, as well as provide some flooding protection. Design of existing WSUD stormwater technologies (such as biofilters, street tree pits, wetlands, porous pavements, etc.) will be further refined for effective collection and pre-treatment of stormwater for subsequent use. In this way, current WSUD measures will be used as treatment barriers distributed throughout urban catchments. At the same time, technologies will be identified and, if necessary, refined for the final polishing of pre-treated water to meet different end‑use requirements. Problems related to water storage in constrained urban environment will also be resolved using innovative and modular stores. For example, linear underground stores that can be easily installed into nature strips and carparks could be considered for precinct solutions, while Aquifer Storage and Recovery technologies could be further refined for regional solutions. These systems will be integrated within existing urban water infrastructure (based on centralised systems) as well the urban landscape. In other words, solutions will be developed for both
P2: Urban Rainfall in a Changing Climate. The future evolution of Australian urban hydrological systems, like any other water resources systems, must be placed into the context of a highly variable climate, particularly on inter-annual timescales. The aim of this project is to develop a sound methodology for the assessment of uncertainties in both the short-term prediction and long-term projection of rainfall events over urban catchments, since reliable rainfall estimation is the key for design of stormwater harvesting systems. Firstly, the most important large-scale weather conditions that govern urban rainfall patterns will be defined, while the accuracy of state of the art numerical models used for their simulation will be evaluated. The Australian community model ACCESS will be the main model used for this work, although the results will be compared against similar calculations performed with WRF and the high resolution (
P4: Stream Ecology. A primary impediment to stormwater harvesting rests with the perception that it will lead to a “starving of urban streams” of their “natural flow”. However, modelling and inferential studies have shown that the opposite is the case; stormwater harvesting is in fact able to restore urban hydrological regimes back towards their pre-development levels (Fletcher et al., 2007), and therefore maintain/restore steam health. However, no empirical study has been carried out to verify these findings. The aim of this project is to determine the impact of stormwater harvesting on the hydrology and water quality of receiving waters, and to assess the subsequent ecological response. This will be undertaken for both a
P5: Risks and Health. Although rainwater harvesting has been practiced for centuries, harvesting of general stormwater is a very recent development in urban water management practice. The stormwater harvesting systems that have been implemented in the past few years, at an ever increasing rate, deliver mainly non-potable water (typically for garden watering and sometimes toilet flushing). It is therefore not surprising that the national guidelines for stormwater harvesting (reuse), which are currently in draft form, recognise that there are major gaps in our understanding of the potential health risks that decentralised stormwater harvesting systems are bringing to our traditional urban water systems. This project aims to resolve outstanding issues related to safe harvesting of general urban stormwater for both potable and non-potable uses on three urban scales: household, streetscape, and neighbourhood. The project will include extensive gathering of data on particular water quality parameters (e.g. toxic chemicals and pathogens) in urban stormwater that we are currently lacking. This data will be gathered across a range of urban catchments to assure their representativeness. Using this data set, as well as the data already collected on more traditional pollutants, risk-assessment based approaches (based on those already used for both potable water and wastewater recycling) will be used to develop improved guidelines for stormwater harvesting.
P6: Society and Institutions. A future under climate change and increasing population will compound the traditional risks associated with climate variability and
P7: Valuation. One of the key challenges for widespread application of stormwater harvesting systems is in the economics of these solutions. Therefore, it is a must that we deliver the economic apparatus that enables evaluation of alternate infrastructure investments. The proposed engineering solutions to water supply and pollution problems, coupled with the scientific modeling of climate change, micro-climate and sustainability, need to be aggregated and incorporated into a dynamic complex systems model of future scenarios to enable a cost benefit appraisal of alternative infrastructure intervention options. Recent advances in economic theory (particularly the fields of game theory, information economics and experimental economics) coupled with computational methods that now allow very complex algorithms to run in very short time, have thrown up potentially far more efficient and manageable allocation mechanisms for access to many public assets. Indeed, it is the ability of governments to harness the power of appropriately designed markets that offers the greatest potential for efficiency and social gain, rather than relying on old planning processes. The project is also about recognizing the substantive governance burden that new solutions to old policy problems raise. When markets and planning processes coexist in a new environmental landscape, the efficacy of proposed infrastructure solutions will be critically dependent on the governance architectures we build to support them. We propose to delve into this complex area by doing joint work with the Society and Institutions project (P6).
P8: Demonstration & Integration Through Urban Design. The benefits of the research insights gained in Projects 1 to 7 can best be realised when used to inform the design of future urban environments at all scales. Urban design of future cities, including retrofits and redevelopment of existing cities, is the integrating process of the research insights and their resulting innovative approaches to transforming cities to water sensitive cities and cities as water supply catchments. The interdisciplinary nature is one of the main strengths of this programme. The aim of this project is to apply the processes of urban design as the instrument for integrating the research insights and their resulting innovative approaches to transforming cities to water sensitive cities that function as water supply catchments. This project will include participation from industry partners in the research programme as well as key stakeholders. The integration of work done on technology, understanding the effects of a changing climate, quantifying micro-climate effects of innovative technologies in urban environments, stream ecology, human health, economics, and society and institutions will provide for the first time a whole-system analysis of the potential of urban stormwater as a viable water resource. The integration of the research insights and resulting innovative approaches from Projects 1 to
(a) Envisioning future urban environments, the water sensitive city, that captures the research insights and associated innovations of the socio-technical-economics dimensions in an integrated framework for future cities;
(b) Back-casting of the envisioned future urban environment to define implementation pathways towards future water sensitive cities; and
(c) Demonstration and pilot projects on the ground, including monitoring of outcomes, at a range of scales, as points of reference for the practical and effective implementation of the identified socio-technical-economics initiatives as key urban design elements, within a changing climatic boundary condition, of the water sensitive city.
With support from the industry partners, at least one demonstration site for each of the three scales (household, streetscape, and neighbourhood, Figure 3) will be established in key Australian urban centres. Both
The research team is gathered from the three leading Australian Universities;
P1: Sustainable Technologies – A/Prof Ana Deletic, Dr Tim Fletcher, Ms Belinda Hatt, Dr Gavin Mudd (Civil Engineering, Monash University) and Dr Shane Haydon (Melbourne Water);
P2: Urban Rainfall in a Changing Climate – Prof Amanda Lynch (School of Geography and Environmental Sciences, Monash University), Prof Michael Reeder and Prof Christian Jakob (School of Mathematical Sciences, Monash University);
P4: Stream Ecology – Dr Tim Fletcher, Ms Belinda Hatt, A/Prof Ana Deletic (Civil Engineering,
P5: Risks and Health – A/Prof Paul Lant (Advanced Water Management Centre (AWMC),
P6: Society and Institutions – A/Prof Rebekah Brown (
P7: Valuation – A/Prof Vivek Chaudhri (
P8: Demonstration & Integration through Urban Design – Dr Tony Wong (EDAW) and Prof David Griggs (Monash Sustainability Institute,
This team has already demonstrated that can they deliver research outputs of high quality and industry relevance. The key researchers are currently leading large research programmes, such as the Facility for Advancing Water Biofiltration (FAWB), National Urban Water Governance Programme (both strongly supported by government and industry). Some of the researchers were instrumental in the success of the CRC for Catchment Hydrology.
To deal with the challenges of integrating teams from different disciplines the overall project will be managed under the framework of the Monash Sustainability Institute which focuses on the management of interdisciplinary research projects on sustainability. The governance structure of the Programme is presented in Figure 6.
Figure 6: The Programme Governance Structure
The following will be put in place:
(1) Programme Stakeholders Board, that will consists of representatives from all industry and university partners, will ultimately be responsible for delivery of the outcomes. The Board will have a Chair who will convene the meetings at least 3 times per year.
(2) Programme Director will chair the Programme Executive and report on progress to both Programme Stakeholders Board, and the Board of Monash Sustainable Institute. S/he will also direct the work of the Operational and Financial Manager.
(3) Programme Executive will consist of all 8 Project Leaders, who will jointly work towards the delivery of research outcomes. The key responsibility of the group will be integration of the work done under each of the eight projects, and assurance of the quality of research outputs.
(4) Operational and Financial Manager will manage day to day business of the Programme. S/he will be responsible for reporting and accounting. S/he will utilize formal project management tools (e.g., PRINCE 2). Progress will be regularly monitored through milestones and deliverables agreed with the founders.
(5) Communication Officer will work on communication of the results and engagement of industry. S/he will also give all necessary admin support, so that the Programme can be run smoothly.
Brown and Keath (2007) Stakeholders perceptions of institutional barriers and drivers to sustainable urban water management in
Fletcher, T.D., Mitchell, V.G., Deletic, A., Ladson, A. (2007). Is Stormwater Harvesting Beneficial to Urban Waterway Flow?, Water Science and Technology 55(4), 265-272
Hatt B.E., Fletcher T.D., Walsh C.J., Taylor S.L. (2004). The influence of urban density and drainage infrastructure on the concentrations and loads of pollutants in small streams, Environmental Management 34 (1): 112-124
Radcliffe, J. (2003). An Overview of Water Recycling in
PMSEIC – prime minister’s Science Engineerinf and Innovation Council Working Group (2007), Water for Our Cities: building resilience in a climate of uncertenty, a report of PMSEIC Working group, June 2007
Wong THF (2006) Australian Runoff Quality: A Guide to Water Sensitive Urban Design, Engineers