Less rain fell into ACT catchments over the past financial year while Canberra households used more water, new figures have shown.
A report by Icon Water into Canberra's drinking water supply revealed an almost 5 per cent increase in the amount of water supplied into the ACT and nearby Queanbeyan during 2019-20.
More than 55,000 megalitres were supplied, up 4.6 per cent on the previous year, while on a per capita basis water consumption increased by 2 per cent.
The increase in water use came as the amount of water in Canberra's catchment areas fell by 1.5 per cent to 55 per cent total capacity, due to below-average rainfall in the area.
Catchment areas were also damaged during last summer's bushfire crisis.
More than 2000 hectares of land that takes in catchment areas at Bendora and Corin Dam were hit by the Orroral Valley fire.
"In 2019-20, climatic events including drought and bushfire in drinking water catchments have presented an elevated risk to water quality," the report said.
While the bushfire itself didn't cause water quality levels to be impacted, subsequent heavy rain in March did.
"Rainfall following bushfires can release inorganic nutrients from burnt plant material and lead to an increase in phosphorus and other nutrients entering waterways," Icon Water said in the report.
"Rainfall events can have a significant impact on water quality."
Icon Water general manager Gerard Brierley said substantial work had been carried out to protect Canberra's drinking supply from bushfires and other natural disasters.
"Our multi-barrier approach to ensuring water quality [is enacted] as far upstream as where the water is sourced, and includes the option to switch between three separate catchments," Mr Brierley said.
In the aftermath of the fire, more than 200 coir logs were placed within catchment areas to prevent water contamination should a bushfire occur.
"Icon Water is also participating in ACT government catchment research programs aimed at improving the quality of water entering source water reservoirs," Icon's report said.
In the past financial year, 84 complaints were made in the ACT about water quality, a 22 per cent drop compared to 2018-19.
The most common cause of complaint was to do with discolouration, followed by issues with odour and taste.