Monitoring the health of our rivers

July 2, 2020

In order to provide drinking water and sewerage services to the community, Icon Water takes water from rivers, usually via dams, and returns treated wastewater to rivers as environmental flows.

Our activities can impact the health of a river in physical, chemical and biological ways, including impacting on other environmental factors such as birds, fish and plants.

River systems altered for human water use can still be healthy, as long as sufficient natural flows are protected and the quantity and quality of nutrients discharged don’t put the natural systems out of balance.

Figure 1 Damselfly nymphs (macroinvertebrates) sampled from the Molonglo River (Photo courtesy of Upper Murrumbidgee Waterwatch)

Why do we have to?

The ACT is located in the Murray Darling Basin where the Murrumbidgee River is one of the major rivers. Australian rivers are protected by federal, state and territory government legislation, regulated via licences and approvals from their respective environment protection agencies. For example, Icon Water has to comply with the conditions of a licence to abstract water (WU67) as well as an environmental authorisation to operate the Lower Molonglo Water Quality Control Centre (LMWQCC) and release treated wastewater to the Molonglo River.  

Icon Water also has to comply with development approval conditions for the construction and operation of infrastructure such as the Enlarged Cotter Dam and the Murrumbidgee to Googong (M2G) pipeline.

Many of our licences and approvals require Icon Water to conduct regular river health monitoring programs.

Figure 2 University of Canberra ecologist sampling riffles in the Cotter River below the Cotter Dam wall

What does it involve?

The health of a river can be measured in a range of ways, for example:

  • Physical properties such as flow volume, flow variability, temperature, turbidity, electrical conductivity, dissolved oxygen and pH. Some of these properties are continuously measured with probes at gauging stations in rivers and reservoirs with the data available online. Other data are obtained from ‘grab samples’ taken at specific times.
  • Physical characteristics such as algae cover on rocks , the amount and type of bank vegetation, sediments in the stream (sand slugs) and in-stream vegetation (reed beds) 
  • Biological properties such as the quantity of nitrogen, phosphorous and pathogens (e.g. Cryptosporidium, E.coli, Giardia)
  • Ecological indicators such as macroinvertebrates and fish. Macroinvertebrates are animals without a backbone that can be seen with the naked eye. Species that inhabit rivers are typically the early life stages of flying insects.  A healthy river in a specific geographic area should have a balanced proportion of different macroinvertebrate species. By sampling the macroinvertebrates in the river and comparing them to the expected range for a healthy river, the river can be assigned a health score. The assessment method is called AUSRIVAS.

The Cotter and Murrumbidgee Rivers also contain populations of threatened native fish such as Macquarie perch, Two-spined Blackfish and Murray cod.  Icon Water is required to monitor these populations as well as threats such as cormorants and introduced fish predators.  

Figure 3 Adult Macquarie perch sampled in the Cotter Reservoir using nets

Who does it?

Our Senior Aquatic Monitoring Officer manages various contracts with specialist ecologists from the University of Canberra, the Australian National University, GHD and the ACT Government to conduct the mandated ecological monitoring programs.

The Officer is responsible for reviewing monitoring reports and engaging with stakeholders and the regulators to maintain compliance.

Biological Monitoring Program Scope
Below Dams
(condition of water abstraction licence WU67)
Macroinvertebrate (AUSRIVAS) and water quality monitoring in spring and autumn each year in the rivers below all the major dams (Corin, Bendora, Cotter and Googong).
Murrumbidgee Ecological Monitoring Program (MEMP)
(condition for the construction and operation of the M2G pipeline and the Murrumbidgee pump-station)
Macroinvertebrate (AUSRIVAS), water quality, algae, vegetation and geomorphology monitoring in spring and autumn each year in the Murrumbidgee River and Burra Creek.
LMWQCC Biological Monitoring Program
(condition of the LMWQCC licence to operate)
Macroinvertebrate (AUSRIVAS), water quality, and algae in the Murrumbidgee and Molonglo Rivers.
Enlarged Cotter Dam fish monitoring
(condition for the construction and operation of the Enlarged Cotter Dam)
Annual monitoring of Macquarie perch, exotic fish (e.g. trout and goldfish) and food resources in the Dam and Cotter River. Monthly cormorant monitoring.
Two-spined Blackfish monitoring
(condition of water abstraction licence WU67)
Biennial monitoring of Two-spined Blackfish in the Cotter River.
Murrumbidgee Fish monitoring
(condition for the construction and operation of the M2G pipeline)
Biennial monitoring of Murray cod in the Murrumbidgee River.

Figure 4 – ACT Government Conservation Research fish ecologists sampling Two-spined Blackfish in the upper reaches of the Cotter River after the 2020 bushfires