Dr Jan Wright said the conversion of beef and sheep farming to dairy farming land had increased nutrient loads on waterways.
''It is almost inevitable that without significantly more intervention, we will continue to see an on-going deterioration in water quality in many catchments across the country, particularly in Canterbury and Southland,'' she said.
''Unfortunately, this investigation has shown the clear link between expanding dairy farming and increasing stress on water quality. Even with best practice mitigation, the large-scale conversion of more land to dairy farming will generally result in more degraded fresh water.''
But its not just about rivers - nitrogen runoff pollutes groundwater, which many of us rely on for drinking. Canterbury's dairy boom has already made some wells unusable, and that trend is only going to continue.
The vested farming interests such as IrrigationNZ are already spreading FUD, but the blunt fact is that "industry best practice" isn't enough. We can't just keep on letting people stick more cows on the land, shitting out more nitrogen into our rivers and groundwater. If we want rivers that are safe to swim in, if we want water that is safe to drink, then we need to stop that process. And that means stocking limits and an overall cap on dairy numbers, almost certainly set well below what we have at present in most areas.
The full report and appendices is here.