Monitoring and Assessing Water Quality

The Department of Water measures the quality of groundwater and surface water (including sediment quality) across Western Australia. This information helps us to manage the state's water resources now and into the future.

The information collected depends on the management question, but may include:

physical characteristics – e.g. temperature, colour, light, sediment suspended in the water
chemical characteristics – e.g. dissolved oxygen, acidity (pH), salinity, nutrients and other contaminants
biological characteristics – e.g. bacteria and algae.

Water quality can be measured by collecting water samples for laboratory analysis or by using probes which can record data at a single point in time, or logged at regular intervals over an extended period.

We use water quality information to assess current condition and patterns over time and space in order to understand and manage the influence of factors such as land use and climate change. This is a complex task requiring consideration of numerous factors. Data collected is compared to a range of guidelines for various human uses and environmental needs

Assessing water quality to manage water resources

The Department of Water uses water quality information to underpin decisions about water resource management. For example, surface water quality is measured weekly in the Swan and Canning estuaries by the Department of Water and the Swan River Trust. This helps us to understand how the levels of nutrients, dissolved oxygen, temperature, salinity and phytoplankton change over time and how best to manage these conditions. An example is the use of oxygenation plants to provide dissolved oxygen to prevent fish deaths and the associated loss of recreational use of the waterway. Water quality sampling

The information also underpins the development of management strategies such as the Swan Canning water quality improvement plan.

Similar water quality monitoring programs are conducted in many rivers and estuaries in the state – see estuary water quality and river water quality.

Water quality has a direct relationship with water quantity - the flow in a waterway or the volume in a water body – hence the department assesses these characteristics together. For example, in the Harvey River below Stirling Dam water quality was analysed in relation to the volume of water released from the dam during hot dry weather. This information helped the department to determine the minimum amount of flow needed to maintain the health of the river downstream from the dam. This helped us to maximise the water available for human use whilst sustaining the river ecosystem and its associated services to our community. See ""Assessment of ecological health and environmental water provisions in the Harvey River" for further information.

Water quality measurement forms part of our assessment of waterway health – for further information see estuary water quality assessment and river water quality assessment.

Accessing data and guidance

The water quality information collected by the Department of Water and other organisations is available from the department's Water Information Reporting (WIR) webpage. Telemetered water level, flow and salinity data at continuously recorded sites for the past 6 days is available at our River monitoring stations page.

A summary of river water quality trends in over 200 sites across the state is provided in the Statewide river water quality assessment.

For guidance about developing a surface water, groundwater or waterway sediment sampling program please contact the department's Water Science Branch. Guidance is also available in these documents: Sampling the Upper Swan Esuary