2019-2022 Catchment Audit

9 AUGUST 2023

The negative impact of climate change has been identified in the latest assessment of the state of Sydney’s Drinking Water Catchment.

The Sydney Drinking Water Catchment Audit 2019-2022 found ongoing reduction in risk associated with water quality and availability, biodiversity and habitat, and land use and urban development.

However, the audit found that climate-driven events, including severe drought, bushfires and subsequent heavy rainfall events combined with cumulative impacts have a negative influence on overall catchment health.

This is reflected in a lack of improvement in key catchment indicators such as the quantity and quality of water captured in the dam. For example the major tributary flowing into Warragamba Dam – the source of 80% of Sydney’s water supply – stopped flowing completely at the end of 2019 for the first time in decades.

The audit – conducted since 1999 - is an assessment of key catchment conditions, rather than a review of WaterNSW’s performance. But as the agency charged with protecting the quality and quantity of water drawn from the Greater Sydney catchment, WaterNSW plays a key role in optimising catchment protection.

The audit notes that since 1999 actions taken by respective government agencies – including WaterNSW – in partnership with industry and the community have reduced many hazards to catchment health.

These positive actions included implementing a range of pollution controls, the restoration and rehabilitation of the natural environment, and policy and decision-making backed by sound evidence.

With respect to climate change the audit states that the risks mean “the security of Sydney’s drinking water is increasingly threatened” by events such as severe drought, floods, heatwaves, storms and bushfires.

The audit report recommends the reduction of greenhouse gases in line with the NSW Government’s net zero emissions and adaptation initiatives to minimise the disruption to management and monitoring caused by increasingly extreme weather events.

The audit includes 24 recommendations to Government aimed at further reducing the risks to catchment health. WaterNSW will review the findings and recommendations in the audit report that are relevant to its operations and report back to government.


The Sydney Drinking Water Catchment Audit is a periodic and statutorily required (Section 42 of the Water NSW Act 2014) assessment of the state of the declared catchment about catchment health indicators including water quality, water availability, biodiversity and habitats, and land use and human settlements.

Several public authorities are nominated by the auditor to implement the recommendations including WaterNSW (lead agency on 12 recommendations), DPE (lead agency on 7 recommendations) and the EPA (lead agency on 2 recommendations).

2019-2022 Catchment Audit Report - PDF, 22391.1 KB

2019-2022 Catchment Audit Appendices - PDF, 3003.04 KB

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