Sixty percent are unsafe is the most commonly used figure. The Government's official report on the matter puts them at 70 percent safe and wants to increase that to 90 percent over the next 23 years.
The river maps at the back of the report they tell us wouldn't have been able to have been chartered 12 months ago, but tell the real story.
There are seven heavy rainfall provinces where dairy farming is the most intensive, and in all of them, from Northland to Southland, the rivers are disproportionately unsafe compared with the rest of the country.
Careful not to upset its farming constituency, the National Ministers were quick to point out that 96 percent of dairy farmers have now, voluntarily fenced off their waterways, which they now have to do. It could be called guilt fencing because the damage had already been done.
The elephant on the river bank though was whether companies bottling water for export should be charged. Conveniently for the Government, a report on that issue isn't due out until the end of the year and after the election.
Nick Smith put up a somewhat unconvincing argument. He has a water bottling plant in his electorate, he told us, just down the road from a Coca Cola plant that uses more than twice as much water. And the local brewer of his favourite beer uses even more water, he said licking his lips.
Why should a water bottling company be singled out and be treated any different from them? he proudly asked.
It shouldn't, they should all be paying!