The Brisbane River winds its way through the Queensland capital and is home to mangroves, CityCats and rowers — but could you drink the water?

From the hills of Mount Stanley to the west and out to Moreton Bay, the river is more than 340 kilometres long and plays a vital role in the city's water supply.

Madonna Grehan grew up in Brisbane in the 1970s and '80s and returns often to visit family; when she's here, she takes a ferry to check the river's condition.

She said she often wondered about its source and what role the river played in everyday life.

The banks of Wivenhoe Dam are popular among day-trippers and campers. ( ABC Radio Brisbane: Jessica Hinchliffe )

"[My father] had a thing about our being able to swim, so wherever we lived we had a swim every weekend at a dam, creek or river," Dr Grehan said.

"At Esk, we swam at Bryden bridge, which is now part of Wivenhoe Dam, and we also swam at Fernvale.

"I think the quality of Brisbane's water is something everyone should put their minds to."

Other respondents to Curious Brisbane have done just that, enquiring about the health of the river and where the city's drinking water comes from.

Can we drink the river water?

Mike Foster from Seqwater said we could, technically, drink water from the Brisbane River depending on which section it was taken from.

"We don't have any of our treatment plants along the main part of the river, but the most important part of the system for us is the mid-Brisbane River," he said.

Wivenhoe Dam is the main source for Brisbane's drinking water. ( Supplied: Seqwater )

"This particular section is 60 kilometres of waterway from the base of Wivenhoe Dam to our Mount Crosby water treatment plant.

"Fifty per cent of Brisbane's drinking water supply comes from Wivenhoe Dam."

Wivenhoe Dam, 80 kilometres west of Brisbane, is the largest water storage area in south-east Queensland, with capacity for more than 1.165 million megalitres at full supply levels.

Water grid facts: 12 dams

12 dams 36 water treatment plants

36 water treatment plants 3 purified recycled water treatment plants

3 purified recycled water treatment plants 1 desalination plant

1 desalination plant 28 bulk water reservoirs

28 bulk water reservoirs 22 pump stations

22 pump stations 600km of water supply pipeline Source: Seqwater

The water travels to the Mount Crosby plant, where contaminants are removed before being delivered to household taps.

Mr Foster said previous droughts had taught the region how to better prepare for dry conditions, with the implementation of a water grid that ran more than 600km of pipes around the south-east.

"During the millennium drought, we had a lot of disconnected water treatment plants that had excess capacity but the water couldn't be moved," he said.

"Back in its day it was the first water grid in Australia. It now allows us to move treated drinking water to and from the Sunshine Coast and Gold Coast, which ensures the water supply stays strong."

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What about seawater or recycled water?

With no significant rain on the radar before Christmas for south-east Queensland, Seqwater believes the Gold Coast desalination plant will begin to operate at full capacity this month to aid Brisbane's water supply.

The plant at Tugun turns seawater into drinking water which is returned to the grid, with the output ramping up during drought conditions.

The desalination plant on the Gold Coast supplements the south-east Queensland water grid. ( Supplied: Seqwater )

At full capacity the plant produces 133 million litres a day.

In addition to the desalination plant, treated wastewater can also be used if drought conditions force supply levels below 40 per cent.

The Western Corridor Recycled Water Scheme sees water intended for recycling sent to treatment plants at Bundamba, Gibson Island and Luggage Point near the Port of Brisbane.

A lot of resources are put into the treatment of water. ( Supplied: Seqwater )

"The scheme can provide up to 180 million litres of water a day; combined with the output from the desalination plant, it can provide a little over a third of what the current region's water demands are," Mr Foster said.

But really, how healthy is the river?

Paul Maxwell from Healthy Land and Water, a not-for-profit group that works to improve Queensland waterways, said when it came to filling up water bottles from the river, it was best not to.

"I wouldn't advise people to drink the water, especially in the estuaries as it's salty and links to Moreton Bay — but it does depend where on the river you are," he said.

Dr Paul Maxwell says the public is becoming more aware about the need for healthy waterways. ( Supplied: Healthy Land and Water )

The most recent healthy waterways report showed the river was healthier than it was 40 years ago, receiving a C-, up from a D+ in 2018.

"We used to treat our river like a toilet," Dr Maxwell said.

"But we have seen a vast improvement with substantial investment to improve the industrial discharges into the river."

The river's health can change dramatically after flooding or heavy rain. ( ABC Radio Brisbane: Jessica Hinchliffe )

The main indicators of a healthy river include water quality, the number of mangroves, seagrass, how many fish call the river home, and the habitats upstream in the catchment.

"The pollutant loads in the catchment are lower this year, as we haven't had any rainfall in the estuary that you can see running through the city out to Moreton Bay," Dr Maxwell said.

He noted that the time of year and rainfall amounts could alter water quality, especially after flooding.

The group holds events to encourage locals to chip in and clean the river. ( Facebook: Healthy Land and Water )

"If it has rained or if the river has flooded, you get a high bacterial load due to the debris that comes into the river."

He said he hoped landholders would continue to make their properties more resilient to flooding, which in turn would protect the catchment for future use when flooding or heavy rain did arrive.