The latest count of platypus in the Upper Murrumbidgee Catchment, stretching from the NSW Snowy Mountains to the outskirts of Canberra, suggests numbers are increasing as the health of waterways improves.

Waterwatch, with the help of dozens of volunteers, has spent the past three years conducting surveys of the monotremes along the Murrumbidgee River, Numeralla River and Cooma Creek in southern NSW.

"We've found that this year we had the same numbers or double the numbers of platypus at our survey sites," Antia Brademann from Cooma Waterwatch said.

"So that's a really good result."

Ms Brademann said Waterwatch river monitoring data showed the health of some sections of the waterways had improved.

"The data is correlating together to show that where river health has increased and ecosystem processes are increasing, then the platypus numbers are also responding in kind."

'Citizen science' making a difference

Cooma Creek runs through the centre of Cooma and had never been considered as a survey site until someone reported a platypus sighting.

"When we surveyed there [last year] we actually found there were two platypus living just downstream of town, which is really amazing because it is quite a small creek," Ms Brademann said.

The pair were spotted again this year.

"We've actually been able to partner with the Snowy Monaro Regional Council to gain some NSW Environmental Trust Funding to improve habitat on the creek and specifically looking at protecting that area where the platypus are," Ms Brademann said.

"So the value of citizen science to help us support our local platypus population is really great."

Low numbers on Canberra's outskirts

Surveys were also conducted along Jerrabomberra Creek and Molonglo Reach in the ACT, with only two platypuses found between the two sites.

"There's a limited population along that stretch of river," said Upper Murrumbidgee Waterwatch facilitator Woo O'Reilly.

"Compared to the Queanbeyan River that is close by where there's an estimated 12 platypus in a stretch of river in the township of Queanbeyan alone."

Direct link between water quality and platypus

Platypus need to eat up to a third of their body weight in water bugs each day, and the healthier a waterway, the more water bugs on offer.

This means there is a direct relationship between the health of a waterway and the number of platypus that it can support.

"When you look at Molonglo Reach and Jerrabomberra Creek there's a lot of weeds in that area and water running off from Fyshwick and coming downstream from the Queanbeyan Sewage Treatment Plant," Ms O'Reilly said.

"There's certainly a lot of pressures on the rivers in those areas and there's certainly room for improvement."

Ms O'Reilly said work was already underway to improve water quality and riverbank habitat along those two stretches of river.

"All these things will improve the chances of more platypus in the future but it takes time to transform into real numbers."