More jobs are being axed in the state's public service sectors that play a big role in regional areas.

WaterNSW joins Transport for NSW and the NSW Department of Regional NSW with 300 more positions going under a round of 'rationalisation'.

Water NSW says around a third of management jobs and a quarter of its workforce will go, bringing the tally of announced job cuts to more than 1,000 in the past few weeks.

"We are performing a fundamental reset of WaterNSW, becoming a leaner, smaller and more focused business, with formal consultation on planned changes commencing today," the spokesperson said.

"We are transforming our business by resetting our priorities, re-focusing on our core purpose, simplifying how we operate, and ensuring we are set up to deliver on our legal and statutory obligations.

"We will work hard to limit customer impacts throughout this period of transition – however, given the size of the funding gap, we may be unable to continue delivering our current functions, activities and projects in the same way."

The Australian Services Union says the news is heartbreaking for workers.

NSW Branch Secretary Angus McFarland says it's another blow for families.

"We will talk to our members to consider what action will we will take going forward," he said.

Minister Rose Jackson met with staff when she visited Warragamba Dam. [IMAGE: WATER NSW]

Nationals leader Dugald Saunders says the job cuts are mystifying.

"Labor’s pillaging of regional NSW is continuing… now with hundreds of jobs on the chopping block at WaterNSW.

"At a time when half the state is under water and the other half is slipping further into drought you need to ask how the Minns Government could possibly justify this decision when our water security is more important than ever.

"Not only is this a critical blow to the important work these employees do for NSW, but it will devastate even more families by ripping these roles from our country communities.

"It’s another gut-wrenching call which once again shows a complete lack of understanding about what our regional areas need."