But for Bruno Ferronato, the critters are key to determining the health and quality of the city's countless waterways.

"These are animals that are more sensitive to pollution, so you get a sense of the water quality just based on the bugs," he said.

"The bugs are able to give a long-term indication of how it's all going."

The Ginninderra Catchment Group Waterwatch coordinator is one of more than 200 volunteers across the ACT that have been monitoring Canberra's 98 catchment areas every month, testing water quality levels alongside the bug catching efforts.

The volunteers played a crucial part in the findings of the latest annual Catchment Health Indicator Program report for 2020, which was released on Monday.

The most recent report on Canberra's waterways found more areas were classified as fair or higher compared to the previous year.

Mr Ferronato said that after years of drought and dry conditions across the territory, many of the water bugs returned to the catchment areas in 2020.

"We had the influence of drought right up until January, and those bugs were not doing well because there was far less water and oxygen," he said. "When we then had lots of rain from February onwards, we had a big improvement in the flows, especially in the upper Murrumbidgee."

Despite the improvement in water quality across parts of the ACT, areas were significantly impacted by debris and other pollutants from the Orroral Valley bushfire, particularly in Canberra's south.

"There was a lot of ash from the fires, and some sections of the Murrumbidgee looked like a chocolate river," Mr Ferronato said.

"The ash and turbidity levels were really high and there were high phosphorous levels as well."

The water quality levels across the catchment areas were tested each month by a small army of volunteers.

Despite testing being suspended for three months due to COVID-19 lockdowns early in 2020, the restrictions did not lead to any loss of volunteer numbers when work resumed.

Ginninderra Catchment Group member Lesley Harland has carried out monthly testing for the past 10 years. She said it was reassuring to see water quality levels pick back up after multiple dry years.

"We did have a big black water event last year just after the bushfires but also there were a lot of dead fish as well," Ms Harland said. "There was a lot of dead carp around the site, and I couldn't believe how low the oxygen levels were. I was so staggered that I had to do the testing twice."

Fellow catchment group member Luke Wensing said there had been a noticeable change in recent months.

"Stormwater drains in suburbs have been cleaned and emptied for the first time in years, and that will mean stormwater will be coming down faster, but the water will be clearer as well," he said.

Launching the report on Monday, ACT Water Minister Shane Rattenbury said it was hoped water quality levels would continue following high flows driven by La Nina weather patterns.