An environmental report due to be made public this morning is expected to indicate the South Island's changing farming landscape is affecting water quality in the region, with it likely to continue deteriorating.
The Parliamentary Commissioner for the Environment Jan Wright will present the report Water quality in New Zealand: Land use and nutrient pollution, which examines how New Zealanders are changing the way they use land and what this means for water quality.
The report is intended to examine the relationship between changing land use and two nutrient pollutants - nitrogen and phosphorus.
Excess nutrients, including nitrogen and phosphorus, can cause weed growth, algal blooms and be harmful to insects, fish and other species.
The report is understood to examine how the large-scale conversion of beef and sheep farming land to dairy farming, particularly in Canterbury and Southland, has increased nutrient loads in waterways.
It is understood Wright will express the view that if the widespread conversion of land to more intensive uses continues, water quality could continue to decline.
The report is expected to fuel debate about the choices between the economic benefits of intensified farming versus the environmental repercussions.
Environment Canterbury commissioner David Caygill said the report would reinforce what everyone in Canterbury already knew.
"If we don't do something, it will get worse. I think that is pretty widely accepted in Canterbury. We get the link between land use and water quality."
Several things were being done to tackle water issues, including nutrient loading, through the Canterbury Water Management Strategy, Caygill said.
It recognised the need to set enforceable water quality and quantity limits for Canterbury's water catchments, he said. Enforceable limits were already in place for the Hurunui catchment.
"The report will help people understand some of the challenges we face in Canterbury. We get the message. Are we doing something about it? Yes. We are."
In a report on water quality last year, Wright said action was needed to improve the quality of rivers, lakes and wetlands.
Stock should be restricted from direct access to water, particularly cattle, and riparian strips of grass should be planted to limit phosphorus entering the water.
Wright's full report will be made public this morning.
- Fairfax Media