River water won’t improve by itself
An interactive map from Statistics NZ shows the Forks Stream near Tekapo has a nitrate concentration of 3 milligrams per litre. About 120 kilometres west at Hinds, the Rhodes Stream has a nitrate concentration of 10.9mg/L.
A little further north, the Boundary Drain reading is
10.3mg/L.
To put this into perspective, the highest nitrate reading is
13.5mg/L in the market gardening capital of the country, Pukekohe.
I often think of that when someone tells me plant-based agriculture will save the planet
but I digress.
One of the differences between the Forks Stream and the waterways near Hinds, is there are 250,000 dairy cows on the flats of South Canterbury and zero dairy cows in Tekapo.
However, that is about to change. Despite many objections, Environment Canterbury has granted consent for a 15,000-cow dairy farm just outside Tekapo.
I am no ecologist but I think I can see where the Forks Stream is heading.
This is a continuation of a trend of adding dairy cows to places they haven’t been before.
But we are also adding cows to places where we already have lots of cows.
Nga¯ i Tahu is still planning on adding 14,000 dairy cows on to the banks of the Waimakariri River.
So, the intensification of the Canterbury plains is clearly continuing. Apparently, ECan’s new directives will require agriculture to reduce nitrate leaching by 15 per cent by 2030 and 30 per cent by 2040.
With these developments in mind, it doesn’t appear ECan is serious about water quality but the Government certainly is.
It made it clear how serious it
is in its discussion document
It has said, from this point onwards, our waterways are not going to get any worse.
Any further intensification cannot have an adverse effect on waterways. Over the next generation, the plan is to restore our waterways to health.
Central government has set new freshwater standards and is giving regional councils five years to draw up plans to manage their catchments in line with the new requirements.
Of course, farmer reaction was not so enthusiastic.
One headline read ‘Farmers despair’ and, judging by rural social media, farmers are indeed despairing.
The always forward-thinking optimists at Federated Farmers said: ‘‘The long-term targets for nitrogen reduction are effectively unachievable in some parts of the country, and will end pastoral farming in these areas.’’
One reason the Feds are claiming the targets are ‘‘unachievable’’ is the reduction in the nitrate concentration target from 6.9mg/L to 1mg/L.
That is an 85 per cent reduction but that does not mean an 85 per cent reduction in per farm nitrate leaching.
When a waterway has a nitrate concentration of 6.9mg/L, the fish will die from actual nitrate poisoning.
Farmers seem to be under the impression that fish can live in anything less than 6.9mg/L and that it is an appropriate target.
But in nature, a fish would have likely died from a lack of oxygen long before the waterway got anywhere near 6.9mg/L.
Slime forms in waterways when nitrate concentrations reach about 0.5mg/L.
The slime absorbs the oxygen from the water, leaving none for the fish to breathe.
The more nutrients in the waterway, the more slime there is and the less oxygen is available for the fish and other critters.
The limit of 1mg/L is a measure of a waterway that is under nutrient pressure but still has some life left in it.
If we allowed our rivers to get to 6.9 mg/L we would have no fish in any of them.
Most New Zealand waterways are well below the 1mg/L mark.
In fact, the top quartile (25 per cent) of rivers ranked by nitrate concentration has a mean of 0.866 mg/L.
There are actually very few rivers that exceed the 1mg/L criteria.
So the waterways around Hinds are in the small minority that exceed the 1mg/L limit.
The freshwater proposals are designed to ensure that those small number of rivers don’t get worse and then actually get better over the next generation.
In 2019, that is hardly an unachievable goal.