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Alternative water sources: this refers to rainwater and urban stormwater.

Catchment: an area where water falling as rain is collected by the landscape, eventually flowing to a body of water, such as a creek, river, dam, lake or ocean; or into a groundwater system.

Community: this includes individuals, public and private landholders, community groups and business owners.

Evapotranspiration: the process by which water is transferred from the land to the atmosphere by evaporation from the soil and other surfaces, and by transpiration from plants.

Gigalitre (GL): one billion (1,000,000,000) litres.

Groundwater: all subsurface water, generally occupying the pores and crevices of rock and soil.

Gross Pollutant Trap (GPT): a stormwater treatment device that is commonly used to remove bulky pollutants such as litter, plastic bottles and leaves.

Impervious area: a surface or area within a catchment that significantly restricts the infiltration of water. Impervious surfaces can include concrete, road surfaces and roofs.

Infiltration: the downward entry of water into the soil.

Megalitre (ML): one million (1,000,000) litres.

Potable: water of suitable quality for drinking.

Rainwater: water that has fallen as rain or been collected from rainfall.

Recycled water: water derived from sewerage systems or industry processes that is treated to a standard appropriate for its intended use.

Riparian: things that are related to or situated alongside a waterway (such as riparian wetlands, habitats, trees etc.).

Runoff: the portion of rainfall which actually ends up as streamflow, also known as rainfall excess.

Stormwater: runoff from urban areas, which increases due to the introduction of impervious surfaces such as roofs and roads within urban development.

Urbanisation: the process by which towns and cities are formed and become larger as more people begin living and working in central areas. It affects the water cycle by increasing the amount of impervious surfaces.

Urban water cycle: the cycle of water through urban environments. Distinguished from the natural urban water cycle by the transfer of water through built infrastructure and the high runoff rates generated by impervious surfaces.

DEECA: Department of Energy, Environment and Climate Action

EPA: Environmental Protection Agency

Integrated Water Management is a collaborative approach to water planning that brings together all elements of the water cycle including wastewater management, water supply, stormwater management and water treatment, considering environmental, economic and social benefits.

Council plays a key role in delivering Integrated Water Management through:

• management of its own water use and provision of community facilities and services that require water, such as aquatic centres and irrigation of sports ovals
• management of local stormwater treatment assets including wetlands, gross pollutant traps, raingardens, swales and tree pits
• management of local civil and drainage assets, such as pits, pipes, roads and small retarding basins
• implementation of the Planning Scheme and related Integrated Water Management requirements
• management and restoration of nature, including public open space, street trees, waterway corridors and wetlands
• working in partnership with other key stakeholders, such as government agencies, community organisations, businesses and residents, and delivery water education programs locally.

Delivery of these water related services are critical and provide significant benefits to the City of Maribyrnong and its community, such as improved physical and mental health, contribution to cooling, local habitat improvements and provision of attractive and enjoyable spaces.

Effective water management ensures the availability of clean and safe water for present and future generations while also minimising the impact on the environment.

An Integrated Water Management Plan will help create a City that is more resilient to projected population growth, increased water demand, climate change and urban heat.

Council currently does not have an Integrated Water Management Plan.

As well as establishing planning requirements, Council plays a vital role in water management directly by managing public assets and drainage, managing its own water use and indirectly through influencing the community’s attitudes and actions. It is important that Council manages the way it uses and cares for water in a manner that is environmentally, socially and financially responsible, to lead by example and influence its community to become more sustainable.

The draft Integrated Water Management Plan will focus on Council’s potable water use as opposed to public or community use, and will help create a City that is more resilient to urban development, climate change and future population growth.

In 2023, Metropolitan Melbourne’s population exceeded five million and officially overtook Metropolitan Sydney as Australia’s most populated city. As one of the fastest growing municipalities within the Metropolitan area, the City of Maribyrnong’s current population of 91,000 is projected to grow by about 30 per cent to approximately 118,000 by 2033 (refer to Figure 1).

This growing population drives urbanisation and an ever-increasing demand for water resources.

With Greater Melbourne’s population predicted to double by 2070, Melbourne Water expects that it will need to double the volume of water supplied to its customers. This equates to an additional 12 GL (or 4,800 Olympic sized swimming pools) of water per year. Taking into account climate change and assuming a ‘high water demand’ scenario, Melbourne may require an additional 85 GL per year by 2030 and a total of 600 GL each year by 2070.

A critical part of meeting this shortfall is having access to a diverse range of water sources. The Central and Gippsland Regional Sustainable Water Strategy2 identified the need to use ‘manufactured water’ such as desalinated water, recycled water and treated stormwater. The plan calls for these sources to make up 14 per cent of Melbourne’s water supply by 2030, climbing to 65 per cent by 2050 and 80 per cent in 2070. Greater Western Water (GWW), the City of Maribyrnong’s water retailer, has also expressed a commitment to diversifying water sources by increasing the use of “alternative water… to increase green open spaces and improve public amenity”. The impact of the Millennium Drought (1997-2009) highlighted the vulnerability of traditional water sources and the need to diversify supply options to build resilience and meet community expectations.

Maribyrnong City Council acknowledged a state of ‘climate emergency’ at the Council Meeting on 19 February 2019 requiring “urgent action by all levels of government.” One of the four main approaches to restore a safe climate outlined in Council’s Climate Emergency Strategy (2020) is “embedding the climate emergency response in Council’s planning, operations, infrastructure, strategies and organisational culture”. Integrated Water Management has a role assisting in climate change mitigation, resilience and reduction of the urban heat island effect, and this plan will further embed it into Council’s processes and operation.

Urbanisation has replaced the cooling effect formerly provided by trees, shrubs, grasses and bodies of water, with hard, predominantly dark, surfaces such as concrete and tiled roofs that absorb and re-radiate heat. This ‘urban heat island’ effect increases heat stress and amplifies the impacts of extreme heat events above what they would otherwise have been. As well as reducing human comfort, the urban heat island effect has been implicated in increased levels of mortality, such that when daily minimum temperature exceeded 30°C average daily mortality for those over 65 increased by 15–17 per cent.

The figure below shows the urban heat island effect across the City of Maribyrnong reaching 6˚C on an average summer day, illustrated by the temperature in industrial areas such as Tottenham, exceeding 31˚C when the local Bureau of Meteorology weather station shows a temperature of 25.5˚C. The temperature is significantly cooler in areas of green space and along Stony Creek and the Maribyrnong River, as shown in blue. Taking into account the effects of climate change, with a predicted increase in warming of approximately 1˚C by the end of this IWM Plan, the figure shows what the temperature in the City is anticipated to be on a 26.6˚C day.

The City of Maribyrnong is predominantly residential, however it also contains numerous industrial precincts (the largest in Tottenham) and commercial and retail areas such as Footscray and Highpoint activity centres. From a water cycle perspective, the catchment is highly impervious, with rainfall in many areas unable to pass through the soil and into the groundwater table, which results in increased stormwater runoff during rainfall events.

While there is significant population growth project for the City of Maribyrnong and residential infill developments are anticipated to continue (i.e. increasing housing density), this does not directly translate to significantly higher imperviousness, as much of the catchment is already developed or impervious. Furthermore, stormwater modelling undertaken has predicted that despite land use changes, there is likely to be an overall decline in stormwater generated throughout the period of the plan due to the reduction in rainfall and increase in temperature (and resultant evaporatisation) expected under climate change.

Mirrangbamurn (Maribyrnong River)

The Mirrangbamurn (Maribyrnong River) is Metropolitan Melbourne’s second largest river and an icon in the west. It is of cultural, social and ecological significance; a place where people come together to connect, exercise and play. It is also a critical habitat corridor for the movement of native animals, including threatened species such as the Growling Grass Frog and Grey-headed Flying-fox.

The river’s floodplain includes two substantial wetlands within the City of Maribyrnong, Frog’s Hollow Wetland (in Pipemakers Park) and Newell’s Paddock Wetland Reserve. These wetlands not only provide important public open space, frog and waterbird habitat, they also improve the quality of stormwater prior to discharge into the Mirrangbamurn (Maribyrnong River).

Stony Creek, once adjacent to quarries, landfills and major industry, now includes areas of community parkland, such as the much-loved Cruickshank Park. While the CREEK still traverses industrial areas, the local community value the public open space as a place to connect with nature and for recreational activities such as dog walking, jogging, playing and cycling.

Both the Mirrangbamurn (Maribyrnong River) and Stony Creek are critical to the amenity, character and natural values of the City, providing important habitat for native animals and refuge to residents from a highly urbanised landscape. The direct connection of stormwater, through the drainage network, to these waterways causes issues such as bank erosion, changes to natural flow patterns and a decline in water quality, aquatic plants and animals. For these reasons it is important that stormwater discharge is minimised and treated appropriately prior to discharge into our local waterways.

In 2017 DEECA (formally DELWP) created a framework for the State Government, water sector and the community to work together to better plan, manage and deliver water in Victoria’s towns and cities. Central to the framework was the establishment of five catchment-scale Integrated Water Management forums across Victoria, one of these was the Maribyrnong Forum.

In 2018 the Maribyrnong Strategic Directions Statement (SDS) was published by the Forum, and a few years later, the State Government delivered a Maribyrnong Catchment Integrated Water Management Plan, which includes the following catchment scale outcomes:

The State Government’s Maribyrnong Catchment Integrated Water Management Plan (2022) provides indicators and measures to drive towards these outcomes including:

• decreasing potable water use / increasing use of fit-for-purpose water source
• reducing the total urban stormwater volume/ decreasing pollutants discharged to waterways
• the percentage of street trees supported by irrigation from an alternative water supply / reducing urban heat for the purposes of enhancing human thermal comfort
• improving the community’s’ connection with and understanding of the water cycle / increasing consideration of the water cycle in town planning.

A number of other organisations are also involved in the delivery of water cycle services in the City of Maribyrnong. Click on the link below to view a table outlining an introduction to each of these, highlighting their key responsibilities and guiding strategic documents in relation to Integrated Water Management. A good understanding of the organisations and their drivers presents opportunities for Integrated Water Management advocacy and collaboration for Maribyrnong City Council.

The role of other organisations

The diagram below provides a high-level summary of current yearly water cycle volumes for the City of Maribyrnong and projected estimates by the conclusion of this plan (2033).

In the last financial year (2022-23) the City of Maribyrnong used 8,133 ML of potable water. Of this, approximately 60 per cent (4,874 ML) was for residential use, and the remaining 40 per cent (3,259 ML) for non-residential uses such as industrial and commercial. Residential use increased over the summer months during this period.

During the 2022-23 financial year, Maribyrnong City Council used approximately 230 ML of potable water. The chart below shows the water use over this period.

Irrigation and maintenance of open spaces, including sports fields, parks and gardens, use the most water, while the largest single ‘building’ use is for the Maribyrnong Aquatic Centre.

The chart below illustrates Council’s annual water use from 2016/17 to 2022/23 by category. It shows that in recent years overall water use has been falling. This is most likely due to 2017/18 and 2018/19 being warmer and drier years than average, and rainfall higher from 2020 onwards, reducing the need for irrigation.

It also demonstrates an approximate 33 per cent reduction in water use at MAC between 2019/20 and 2021/22.

A large percentage of Council’s total water use is correlated with the need to irrigate parks and sports fields for community use. On this basis, it is assumed that irrigation, and the impact of climate, will continue to be the main driver behind Council’s water use. This is based on the assumptions that:

• Council will continue to irrigate open space to provide greener, cooler spaces for the community
• there will be irrigation of new open spaces associated with redevelopment and creation of new open space, in accordance with the Open Space Strategy
• growing population density may mean that additional irrigation will be required to maintain current and expected levels of service.