6.2 Introduction

This chapter assesses the state of the Australian Capital Territory’s (ACT’s) water resources, including trends in the quality and availability of surface water, groundwater and drinking water; and river flow and ecological condition. It also examines the major pressures affecting water in the ACT, such as land use and climate change, and how these pressures affect the ACT’s water.

This chapter will:

• describe the ACT’s water resources
• explain why water is important
• describe indicators used to assess water resource condition
• assess the limitations of current monitoring of water resource condition
• describe the current state of water resources in the ACT
• assess whether the condition of water resources is stable, improving or declining
• describe the pressures on the ACT’s water resources and the impacts these pressures are having
• assess whether the impacts from pressures are stable, increasing or decreasing
• summarise government response mechanisms.

6.2.1 What are the ACT’s water resources?

The ACT draws water from three separate catchments (Figure 6.1):

• the Cotter River Catchment and its three reservoirs: Cotter, Bendora and Corin
• the Queanbeyan River Catchment, which supplies the water held by Googong Dam in New South Wales (NSW)
• the Murrumbidgee River Catchment, via the Cotter Pumping Station and the Murrumbidgee to Googong water transfer.

Source: Map provided by Icon Water

Figure 6.1 ACT water supply network

The Murrumbidgee River is the major river flowing through the ACT, originating in the alpine area to the south of the ACT. All rivers and creeks in the ACT drain to the Murrumbidgee River. The longest of these are the Molonglo and Queanbeyan rivers, which originate to the south-east of the ACT and together drain through Lake Burley Griffin before flowing into the Murrumbidgee River.

In urban areas, there are numerous constructed lakes and wetlands, as well as natural wetlands, including Horse Park Wetlands in Gungahlin and wetlands in conservation areas in the southern half of the ACT. There are also groundwater aquifers that store and discharge water into water bodies throughout the ACT.

6.2.2 Why is water important?

Water underpins almost every aspect of life and is a vital component of the households, landscapes and urban environments of the ACT. Without enough clean water, people could go without drinking water,¹ agricultural productivity could be jeopardised,² and ecosystems could become degraded.³

Water is both a local issue and one that connects us to the global hydrological cycle. Global climate change has already affected the water cycle and is likely to affect rainfall in our region. Since the mid-1990s, late autumn and early winter rainfall has declined in south-east Australia, and it is predicted that the region will become hotter and drier in the future^4–6 (see Chapter 2).

Given water’s central role in society and the environment, and the pressures and challenges facing water supply in the ACT, it is imperative that we monitor and assess the condition of our water resources so that we can manage them effectively.

Water and human wellbeing

Human wellbeing is closely tied to the availability of clean and abundant water. Water makes up around 70% of the human body and plays an essential role in biological processes.

Water is also an important component of our urban environment. Canberra’s lakes, ponds and constructed wetlands improve biodiversity, aesthetics, heat mitigation and recreational opportunities – thereby supporting human wellbeing. The many water resources in the ACT also support a range of recreational uses, as well as urban and rural activities. Water is also vital in the maintenance of sporting ovals and other green areas that contribute to the fitness, health and social wellbeing of ACT residents (see Johnstone et al⁷).

Production of the food and fibre that we depend on also relies on water. The ACT is located in the south-east of the Murray–Darling Basin, one of the most important agricultural regions in the country. In 2012–13, the basin accounted for more than 70% of water used in agriculture nationally.⁸ The region produces more than half of Australia’s irrigated agriculture, worth $6.8 billion in 2012–13.

The effect of droughts and prolonged dry periods demonstrates our dependence on water, and how individuals, communities and economies suffer when water is in short supply. For instance, as a result of the 2002–03 drought, farm gross domestic product and rural exports dropped by around one-quarter, agricultural income fell by 46% and around 100 000 jobs were lost.⁹ Droughts also affect ecosystems and, ultimately, human wellbeing. For example, reduced volumes of water and higher temperatures in water bodies, rivers and streams can decrease water quality and increase the risk of algal blooms – with negative consequences for fish, stock and domestic animals, and people. Extended dry conditions can also result in habitat loss on the edges of water systems and depleted biodiversity in floodplain rivers.

Ecosystem services

The water cycle plays an integral part in the planet’s climate, chemistry and biology.¹ The water cycle connects water bodies, land, biodiversity and the atmosphere through the stages of precipitation, infiltration, run-off, evaporation and transpiration. Without a functioning water cycle, many of the natural processes that enable and support life would cease to operate.

Water both provides ecosystem services and is affected by other ecosystem services. Healthy soils, terrestrial environments and aquatic ecosystems help to filter and purify water after it falls as rain and snow, before it flows into our rivers and streams, and before it is collected and distributed for human use. The quality of water can decline significantly when it passes though ecosystems and soils that have been degraded by poor management, or disturbed by events such as fire.^10–13

6.2.3 How do we measure water resources?

The condition of water resources in the ACT is influenced by the different ways in which water is used, and by surrounding land use. Different land uses have different effects on water quality (eg different rates of soil erosion and sediment transport occur in areas with different land uses) and hydrology (eg impervious surfaces in urban areas increase stormwater run-off and locally reduce groundwater recharge).

There are five major land uses in the ACT (Figure 6.2). Each land-use group affects water quality differently:

• Conservation and natural environments tend to have a minimal negative impact on water quality in normal circumstances.
• Production from dryland agriculture and plantations, irrigated agriculture and plantations, and natural environments can have significant impacts on surface water and groundwater. For example, some rural activities that clear vegetation may result in soil erosion. On-farm water retention may reduce surface water in creek lines and locally deplete groundwater. There is potential for the release of agricultural chemicals and animal waste, which may add to the nutrient load of waterways. In addition, run-off following storms may have negative effects on local water quality (eg as fine sediment inputs).¹³
• Intensive land uses (eg urban areas) have the greatest potential for negative impact on local water quality. Fertilisers and other chemicals, organic matter, soil, oil or sewage effluent entering waterways can negatively affect the health of our freshwater environments. Urban development modifies natural drainage lines and riparian areas, and impervious surfaces alter the flow of water across urban areas. Changes can markedly reduce biodiversity, and promote conditions suitable for undesirable aquatic weeds and nuisance algae. However, water-sensitive urban design measures can ameliorate the impact of urban development on water quality and flows.

Source: Based on data sourced from the ACT Government for Dyer et al¹⁴

Figure 6.2 Upper Murrumbidgee Catchment (including the ACT) waterways and land uses

To assess how water resources in the ACT are responding to pressures from land use, climate and water resource development, we examined a range of water-related indicators that reflect the amount, quality and ecological condition of waters in the ACT.

Data on these indicators are collected at different places and times throughout the Territory to help us understand the current condition (state) of water resources in the ACT and how their condition is changing over time (trend).