Scientists have found that dairy runoff into the country's rivers is decreasing in areas where significant measures to reduce the problem are in force.
The National Institute of Water and Atmospheric Research (NIWA)says fencing, adding vegetation near waterways and using effluent for irrigation have significantly improved water quality and clarity, with reduced levels of e.coli and particulate phosphorus.
NIWA scientist Dr Bob Wilcock, who has done a 10-year study of how to reduce the impacts of pastoral runoff into waterways, says the findings come from Waikato, South Taranaki, Canterbury, Southland and the West Coast.
He says they show more farmers are fencing off rivers and streams through their properties, which helps to reduce sediment runoff, but more work is needed.
He says levels of nitrogen and dissolved phosphorus remain high in nearly all sites, but over time there should be a significant decrease.
Dr Wilcock supports a national approach to reducing pollution from farms, saying a bottom line on water protection needs be established.