Indicator assessment
CONDITION
TREND
DATA QUALITY
The variation in water storage volumes is consistent with a long-term trend in the ACT of extended periods of reduced storage inflows punctuated by years of high rainfall. The ACT’s four reservoirs were holding just 55% of the total ACT storage capacity in June 2020 but very high annual rainfall resulted in full, or close to full, storage capacity for all reservoirs from 2021 to June 2023. However, the long-term trends in storage volumes and inflows show that although recent years have provided above average water resources, the region remains prone to long periods of dry conditions with implications for water resources.
CONDITION
Environmental condition is healthy across the ACT, OR pressure likely to have negligible impact on environmental condition/human health.
Environmental condition is neither positive or negative and may be variable across the ACT, OR pressure likely to have limited impact on environmental condition/human health.
Environmental condition is under significant stress, OR pressure likely to have significant impact on environmental condition/ human health.
Data is insufficient to make an assessment of status and trends.
TREND
DATA QUALITY
Adequate high-quality evidence and high level of consensus.
Limited evidence or limited consensus.
Evidence and consensus too low to make an assessment.
Assessments of status, trends and data quality are not appropriate for the indicator.
Introduction
For information on this indicator see Background: Human Settlements.
This section examines the availability of water resources in the ACT. For information on aquatic ecosystem health, water quality and river flows see section Water. Groundwater resources and use are not reported.
The volume of water resources in the ACT’s reservoirs (storage volumes) is determined by inflows from rainfall, decreases in volume are determined by the amount of water consumed, evaporation, spills and releases for environmental flows. This means that changes in the storage volumes of individual reservoirs will be highly variable, regardless of inflows. This is particularly the case for the Cotter catchment reservoirs which are generally the main sources for ACT’s water.
Water resources
From June 2019 to June 2023, storage volumes were highly variable for all ACT reservoirs in response to annual changes to inflows and water use (Figure 24). The ACT suffered drought conditions from 2017 to 2019, with conditions in 2019 being particularly severe (see Climate change). This led to the lower storage volumes in June 2019 and June 2020, and followed a pattern of generally drier conditions from 2013. At the end of June 2020, the ACT’s four reservoirs were holding just 55% (157 gigalitres) of the total ACT storage capacity. However, the high rainfall from 2020 to 2022 resulted in full, or close to full, storage capacity for all reservoirs from 2021 to 2023.
Figure 24: Total storage volumes for ACT reservoirs and total accessible water storage (right axis), June 2015 to June 2023.
Data sourced from: Icon Water.
The variation in water storage volumes is consistent with a long-term trend in the ACT of extended periods of reduced storage inflows punctuated by years of high rainfall. From 2001–02 to 2019–20, all but two years (2010–11 and 2011–12) had total inflows to storages that were below the long-term average (Figure 25). The total inflows during 2018–19 was 33 gigalitres, the lowest since records began in 1912 and 86% below the long-term average. The wetter years from 2020–21 to 2022–23 provided inflows that were much higher than the long-term average, with 602 gigalitres of inflows in 2021–22 — more than two and a half times above the long-term average.
Figure 25: Total inflows to the ACT’s four water storage reservoirs, 2001–02 to 2022–23.
Data sourced from: Icon Water.
The long-term trends in the ACT’s storage volumes and inflows show that although recent years have provided above average water resources, the region is prone to long periods of dry conditions. Consequently, water resources remain a concern with climate change and a growing population continuing to put pressure on the ACT’s water resources.
Wastewater recycling
The Lower Molonglo Water Quality Control Centre non-drinking water scheme is the primary supply of recycled water in the ACT. The main driver of recycled water use is rainfall, with periods of high rainfall vastly reducing the need for recycled water.
Although there was some use of recycled water between 2009–10 and 2018–19, recent years have seen a shift away from the use of recycled water, primarily as a result of the end of the millennium drought and the suspension of the North Canberra Water Recycling Water Scheme and the pilot Southwell Park Recycled Water Facility.
Despite the wetter conditions in recent years, periods of drought in the future may increase the viability and demand for recycled water.
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