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Despite the best efforts of many and some undoubted successes, water quailty overall is expected to decline as intensive dairying expands, says Jan Wright in a major new report

Rural News
Despite the best efforts of many and some undoubted successes, water quailty overall is expected to decline as intensive dairying expands, says Jan Wright in a major new report
Periphyton in the lower Rangitīkei River in 2013.

The following is the Conclusion in the Parliamentary Commissioner for the Environment's report released today on water quality.


“The health of our waters is the principal measure of how we live on the land”

Over recent years, water quality has become a subject of high public concern and vigorous debate in New Zealand.

This investigation has explored the relationship between land use and the two nutrient pollutants that cause water quality problems – nitrogen and phosphorus.

Most of the nitrogen that ends up in fresh water has its origin in animal urine.

Nitrogen is ‘elusive’; it exists in highly soluble forms that readily leach through soil into groundwater. This makes it difficult to mitigate – to keep out of water.

Much of the phosphorus that ends up in water began as naturally occurring phosphorus in soil, and has been carried into water over many decades through erosion.

Phosphorus is ‘sticky’; most of it is attached to soil and sediment. On the one hand, this makes it relatively easy to mitigate.

On the other hand, when it gets into water it accumulates in the sediment on riverbeds and lakebeds, although some will be flushed out in rapidly flowing rivers.

This report is based on results obtained by linking two models. The first, known as LURNZ, is a simulation model of land use change.

The second, known as CLUES, can be used to estimate the nutrients lost from land to fresh water at a catchment scale.

Over recent years, shifting commodity prices have led to many sheep/beef farms on relatively flat and fertile land being converted to dairy farms. At the same time, large areas of hill country sheep/beef land have been planted in forest, and some have been left to revert to unproductive scrubland.

The LURNZ model predicts that these trends will continue.

The amounts of nitrogen and phosphorus travelling off land into water depend to a large extent on how the land is used. For instance, in a heavily forested catchment, there are few animals producing nitrogen-rich urine and phosphorus-rich dung, and the tree roots hold the soil (and the phosphorus it contains) on the land. In catchments dominated by pasture, especially dairy pasture, nutrient loss rates are much higher.

Consequently, when land uses change, the amount of nitrogen and phosphorus that is lost from the land into water also changes.

The land use change results from LURNZ have been ‘fed in’ to the second model – CLUES – to estimate their impact on the tonnes of nitrogen and phosphorus being added every year into the streams, rivers, lakes, aquifers and estuaries in different regions of the country.

The modelling shows annual nitrogen loads on fresh water continuing to rise in virtually every region. Figure 7.1 shows how these increasing nitrogen loads correlate with the expansion of dairy farming. Canterbury, Southland, and to a lesser extent, Otago, stand out. Other regions have lesser increases, although some, such as Waikato and Manawatū, already have high nitrogen loads and existing water quality problems. The increases in nitrogen loads shown in Figure 7.1 are regional averages. In some catchments, they will be much greater, and in other catchments much smaller.

The modelling shows much smaller changes in the annual phosphorus loads. The only significant increases between 1996 and 2020 are in Canterbury and Southland: 9% and 10% respectively.

In some regions, annual phosphorus loads are decreasing.

Nevertheless, much of the phosphorus entering fresh water will continue to accumulate in sediment.

Because dairy farming has expanded so quickly and is known to have high nutrient loss rates, mitigation has become a major focus of changing farm practices.

The modelling for this report has been done assuming that by 2020 reductions in nutrient losses from mitigation will offset increases from more intensive use of the land. This assumption is optimistic. Mitigation may be able to ‘hold the line’ or even reduce nutrient losses in some cases.

But mitigation cannot offset the increase in nutrients that comes from large-scale change to more intensive land uses.

While new dairy farms converted from exotic forests in the central North Island may employ extensive mitigation techniques, the nutrient losses are still at least ten times higher than they were when the land was covered in trees.

In catchments where there has been large-scale land use change to dairy farming the gains made by increased mitigation are swamped.

Excessive levels of nitrogen and phosphorus in fresh water make it too fertile, leading to accelerated plant growth and algal blooms, degrading swimming and fishing spots, and damaging fresh water ecosystems. At very high levels, too much nitrogen is toxic to fish and other aquatic life.

While water quality is complex, the science has established clear relationships, and these are well understood and accepted.

Although much depends on natural factors like flow rate, water quality tends to be worst in areas where nutrient loads are highest.

It has been theorised that in some cases nitrogen loads are less important, because the growth of excessive plant growth could be controlled by focussing on managing phosphorus. This may be possible under the right conditions, but relies on many factors being in alignment.

Such an approach would not, for example, protect the many nitrogen-limited estuaries which are already especially vulnerable because they lie at the bottom of catchments.

The passage of time may reveal a different land use future to the one forecast by the modelling. If, for instance, dairy farming expands more slowly and forestry expands more quickly, then nitrogen and phosphorus loads will be lower than predicted.

But the opposite, if anything, appears to be the case.

Unfortunately, if we continue to see large-scale conversion of land to more intensive uses, it is difficult to see how water quality will not continue to decline in the next few years.

This is despite the best efforts of many and some undoubted successes.

Understanding the links between land use, on-farm practices and water quality is essential for developing policies that achieve good outcomes – healthy rivers, lakes, estuaries and aquifers.

Hopefully, this report has clarified and deepened that understanding.

We welcome your comments below. If you are not already registered, please register to comment.

Remember we welcome robust, respectful and insightful debate. We don't welcome abusive or defamatory comments and will de-register those repeatedly making such comments. Our current comment policy is here.


If NZ moved to Dairy Factory farming like they do in many other countries the Nitrogen problem could be solved by using bio reactors to process the effluent like they are starting to do on pig farms.

The cost of milk in other Countries(eg China) is high because the feed costs are so high. NZ has lots of grass so couldn't we have the best of both worlds with increasing milk production and decreasing environmental costs? 


This comes as absolutely no surprise.


To a certain extent, it will be mitigated when the business model - it's fossil fuel; based and they're down to fracking; scraping the second half of the barrel - falls over.


But the effect will be more to compound things. Environmental impacts go out the door when you're faced with paying the bank, and fuel costs have hit your bottom line, and those of your customers.


Water quality will determine NZ's long-term prosperity.


Could you expand slightly?


Greedy highly-leveraged dairy farmers are pouring on the nitrogen to grow grass and make more money. They don't care about the long term damage to NZ's waterways. Time for a Nitrogen Tax!



It would be helpful if you reread the article and educate your self , fertilzer nitrogen is not the problem urine from all mammals is

i find it interesting that you get pleasure from criticising those who put food on your table obviously it too cheap   


Micks is actually quite correct, you see, more nitrogen fertiliser = more grass = more animals = more poos and wees going into the ground water.

The problem is, as with all forms of poultion, is the time lag effect.


Our waterways will get worse before they get better because of what we were putting on the farms decades ago - think of the top soil as a big sponge - it takes time to soak through into the gound water.



Watch this space Bernard Hickey - its like the ghost of the post of Allan Hubard that you cencered all those years ago - ..... 


Think of plant roots as a  filter which strip out nutrients in the 'sponge'.


According to the labour party farmers (multiple farm owners) make more money from capital gains, and they're probably right.

Fert N allows you to grow more grass provided suitable climatic conditions. To make money from it you need the skills to utilise the grass. I suppose another way to 'profitably' utilise that artificially boosted grass is a high stocking rate, which could put pressure on ground water quality. This is a system employed by some multiple farm owners. Another model would be like LandCorp, and spend mega bucks and not appear to stress about making a profit, but I don't know if that would have a positive contribution to GDP?


So do farmers make money operationally or speculatively?


Another load of rubbish written by a money hungry civil servant. These modern greenies (along with councils) are parasites who gravitate to whoever's making the most money. Councils on the one hand are trying to initiate large scale irrigation schemes to increase dairy farming, so that they can make money from consents and environmental restrictions. City investors are driving up prices for farmland as their greed for an easy buck requires farmers to make more money. As for the comment about hill country land being planted into pine trees, I think this is wishful thinking. Most hill country farmers in our area are doing a bit of farming, a bit of manuka honey, a bit of tourism, a bit of fishing, etc.

People forget that every year, in this country our forest parks have thousands of tons of 1080 poison dumped on them. (100% pure NZ yeah right!)

  The fencing of the waterways is a flawed policy, thought up by an audi driving greenie civil servant who knows nothing about the environment. It is not sustainable in the long term. If you permanently fence of waterways they will grow weeds, like gorse and blackberry. These weeds will clog waterways and gorse seed once established , stays in the ground for 100 years requiring constant spraying. Councils know this and this will grow their business as thousands of kilometres of waterways will require spraying and cleaning consents.

 Modern greenies are trying to make money! They are not the pot smoking hippies they used to be. They start environmental companies.

 If you think you are interested in the environment, take a look around your house.... how many chinese made goods do you own? The western world is addicted to cheap goods made in china, the largest burners of coal in the world. How many  cell phones have you owned in your life? 5? 10? 15? We are addicted to consumption.

So if you want your cake and eat it , keep believing the rubbish they write in articles like this.



excellent stuff tim.
Intensification on land is not helping, but in NZ those same people screaming for nutrient control are the same NIMBYs that oppose any form of contained farming.  They're also usually the ones calling for higher interest rates and taxation and wages, to reduce "inflation" that just results in less money to fix the problems on farm and in business.

I have yet to see a water quality report that addresses the speed of transfer for surface and ground waters. 

We were told fencing out stock was the magic bullet.
Now that it's proving that it caches nutrients and concentrates them in the riparian zone, in a highly active ecological niche, rather than having the well paid audi drivers fix their errors; we're being told that it must still somehow be the farmers fault - despite farmers predicting exactly the results they're getting.    egads, it's almost as if some farmers know about soil and growing plants!


"If you think you are interested in the environment"

LOL, while I dont agree with much you have said I certianly agree with this one.

Seems many ppls ideas of being green is install a low energy bulb and carry on driving their dogs in their SUV out to the countryside for a bit of exercise.  Then whine if they see a windmill or a cow patt in the process.

Cell phones, think Im on my third, sadly my second had to be binned, after after 6 years the case fell apart and I couldnt get a new case....pity the battery lasted over a week...this new one 3 days....

The pollution in the water ways though is a huge concern it has to be fixed.

Personally I think the biggest issues for us is being "debt junkies" that enslaves us and drives farmers to exploit the environment ever more, its diminishing returns and lacks resiliance. The correction is going to be huge....



@tim12-i get what u r saying: gorse seeds were shown to last for more than 900 years after a church that age was demolished in the UK and up came gorse.

A scientist said that water quality is temporary (can't remember who dammit), so when the dairy runoff stops, it wont be long before the water clears up.

Maybe once the dairy farmers pay for their land some of them might go right i'm sick of dairy cows, let's do beef or sheep. Some will just go for the $$ but it'll be interesting to see how land use changes over time.

While i'm at it, how come no-one seems to notice the pollution from human bodily wastes that goes into water? Last time i checked the local govt. act they'd cut out any info that the public could get.

Reminds me of something i heard an autioneer said when a woman said about a pot he was auctioning "it's got a hole in the bottom" he ad libs mid speel: " so have u so have i two in yours one in mine" Translation: wer'e all hypocrites.


Comment from a reader via email:


Subject water pollution, due to excessive algae. I am not familiar with your country's water pollution regulation, but I have to assume that they are similar to those in the USA and Europe. If they are they will also use an essential test incorrect and not only ignore 60% of the oxygen depletion pollution, but all the nitrogenous waste (urine and protein),while this waste also is a fertilizer for algae and for each pound capable of growing 20 pound of new algae. The incorrect use of this BOD test, developed around 1910 in England, by using its 5-day reading in stead of its full 30-day reading, is apparently so embarrassing that it is going to take more than 30 years to correct this test in the USA, after we now experience dead zones in most our open waters. Here too they blame the runoffs from farms and cities and although such runoffs contribute to excessive algae growth, the main reason still appear to over up this testing mistake that caused the failure of the Clean Water Act, the second largest federally funded public works program. You may want to find out how this Biochemical Oxygen Demand (BOD) is performed in NZ.

Regards, Peter Maier, PhD,PE


Mr Chaston

No point in just posting it here. Obviously If your reader is correct  it is serious.

If you are really a responsible Kiwi, and a good journalist, you would be passing it on to appropriate authorities, get an answer, and publish the answer for all to see.

Just putting a post in among a whole bunch of comments does not cut it.


The report, when read in full has some interesting reading.

On a per hectare basis, the highest losses of nitrogen come from land used for market gardening, in part because vegetables do not take up nitrogen efficiently.10  The lowest nitrogen loss per hectare comes from forested land and scrub. Losses from livestock farming lie in between.     Leaching rates of nitrogen are particularly high when cattle are break-fed in winter on forage crops such as swedes. Not always true.  Environment Southland this winter conducted some actual leaching testing on waterways where crops were being fed on two properties in the Waituna Catchment - one a sheep farm and one a dairy farm.  The nitrogen leaching was way below the acceptable level on both farms (which surprised) with the dairy farm leaching being lower than the sheep farm (an even bigger surprise).    Thick mats trailing tendrils of brown slime can be seen in many lowland streams and rivers in summer.14 Then we go to the explanation of 14 and we find it is actually referring to Didymo - an introduced weed by recreational fishers - nothing to do with farming.   14 Didymo is a type of periphyton that blooms only in very low nutrient rivers. This is because the bloom, of carbohydrate stalks, is actually the organism’s reaction to low nutrient water (Kilroy and Bothwell, 2011).      Is didymo the elephant in the room in relation to degradation of 'clean' rivers/lakes especially in the South Island? Didymo threatens aquatic habitat, biodiversity and recreational opportunities........Unlike many other aquatic invasive plants, didymo grows on the bottom of both flowing and still waters. It is characterized by the development of thick mat-like growths (blooms), which can last for months, even in fast flowing streams. During blooms, these mats may completely cover long stretches of stream beds, altering stream conditions and choking out many of the organisms that live on the stream bottom, which can affect trout and other fish by limiting their food.    There are many ways in which nutrient losses can be mitigated. These include: • Disposing of town sewage and dairy shed effluent on to land, thus using it as a fertiliser. Fonterra bans the use of human sewage (even if treated) as a fertiliser, bans the use of crops e.g. grass or lucerne fed with human waste fertiliser, as a feed on dairy farms, and bans the use of land that has had human waste fertiliser applied for three years after the last application.  Rotorua City Council has made 'Gardeners Gold' sewgae based fertiliser/compost available for years to the city gardeners. A Council 'ahead of its time?' • Planting poplars, willows and other trees to hold the soil on erosion-prone hill country. Some regional councils ban the planting of poplars and willows on erosion prone soils and have actively destroyed such trees growing in these situations. • Fencing gullies and letting them revert to native bush. • Nutrient budgeting to avoid using excess fertiliser.  It is a condition of supply to Fonterra. • Fencing streams and bridging crossings to exclude cattle thus reducing both direct deposition of dung and urine and erosion of banks.  • Planting riparian strips along stream banks so that nutrients will be absorbed by growing plants before they reach the water. As noted by Tim above in some cases fencing of streams in reality is not meeting the theory of the benefits. The report acknowledges that the benefits of this is on phosphorus not nitrogen. • Keeping cattle off pasture at critical times using concrete stand-off pads and wintering barns. • Constructing wetlands in low-lying areas.  Research is due to start on this in the Waituna catchment shortly.  Testing done on our (natural) wetland has shown definite nitrogen reductions, almost nil on phosphorus and substantially increased e-coli readings where water fowl settle.       The rise of dairy farming is not without issues. Irrigated land in particular has high nitrogen leaching according to Overseer. In Southland you now have to get a consent to convert a sheep farm to dairy - it is no longer a given right. This has slowed the rate of conversions down markedly in Southland.  The report doesn't appear to have taken this in to account in regards to Southland, or the nutrient caps/loading restrictions that regional councils are/have brought in.