A report on cleaning up the Waikato River is recommending measures that could cost between $1 billion and $1.5 billion over 30 years.
The 269-page report has been written by the National Institute of Water and Atmospheric Research for the newly formed Waikato River Authority.
The study comes up with 60 priority actions needed to rehabilitate the river. These range from good governance to reducing pollutant runoff from farmland and pollution from urban areas.
It provides economic analysis and modelling over 30 years and arrives at a top figure of $4.8 billion.
The report says the economic effect will be small because the recommendations will stimulate the local economy at the expense of only a small contraction in the rest of the country.
Waikato Regional Council says the responsibility for cleaning up the river lies with everyone, not just farmers.
Regional council chairman Peter Buckley says it is not just up to the agricultural sector to stop polluting the river.
Mr Buckley says the cost of the cleanup must be shared between central and local government and industry.