An expected tightening of freshwater regulations could force southern farmers out of business, Clutha-Southland National MP Hamish Walker says.

Environment Minister David Parker and Agriculture Minister Damien O'Connor will today announce a plan aimed at stopping the degradation of New Zealand waterways and improving freshwater quality.

Walker said if what he heard about the announcement was correct, it would ''severely hurt'' the southern economy.

He was told there would be significant changes to the National Policy Statement on Freshwater, including a ''serious'' tightening of baseline water quality monitored by regional councils.

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Councils would be required to have plans to meet these standards notified by 2023, and operative by 2025, earlier than the previous 2030 deadline.

There were also many changes expected in rules to govern farm practices, especially those with intensive land use.

He was told to expect farm environment plans for dairy and sheep and beef farms, stock exclusion requirements, and new rules for intensive grazing.

Changes in land use would become much more difficult.

The cumulative impacts of these changes would be ''economically severe'', he said.

''There was always more to be done, and farmers are the first to put their hands up and say we can do more, but rather than building on this, the Government are saying that's not good enough.''

Environment Minister David Parker said he had no comment other than the announcement would be a discussion document containing options.

Some of Walker's information was correct and some was not, he said.

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Otago Regional Council chief executive Sarah Gardner said the council was waiting to see the full content of the announcements before saying more about how they would affect its work.

An Environment Southland spokeswoman said it had not received the content of the announcement and did not comment on what Walker thought was in it.

Fish and Game chief executive Martin Taylor said with a proposed change in regulations, the Government had a ''once-in-a-generation opportunity'' to tackle an issue New Zealanders were deeply concerned about.

''Kiwis expect to be able to swim, fish and gather food from their rivers, lakes and streams.

''People are calling for change so their children's children can have a New Zealand they are proud to call home.''